diff --git a/docs/library/esp.rst b/docs/library/esp.rst
index 8920c8241ea0..9c20b5e8b2d8 100644
--- a/docs/library/esp.rst
+++ b/docs/library/esp.rst
@@ -62,12 +62,35 @@ Functions
 
 .. function:: flash_erase(sector_no)
 
-.. function:: osdebug(level)
+.. function:: osdebug(uart_no)
 
-    Turn esp os debugging messages on or off.
+    .. note:: This is the ESP8266 form of this function.
 
-    The *level* parameter sets the threshold for the log messages for all esp components.
-    The log levels are defined as constants:
+    Change the level of OS serial debug log messages. On boot,
+    OS serial debug log messages are disabled.
+
+    ``uart_no`` is the number of the UART peripheral which should receive
+    OS-level output, or ``None`` to disable OS serial debug log messages.
+
+.. function:: osdebug(uart_no, [level])
+    :no-index:
+
+    .. note:: This is the ESP32 form of this function.
+
+    Change the level of OS serial debug log messages. On boot, OS
+    serial debug log messages are limited to Error output only.
+
+    The behaviour of this function depends on the arguments passed to it. The
+    following combinations are supported:
+
+    ``osdebug(None)`` restores the default OS debug log message level
+    (``LOG_ERROR``).
+
+    ``osdebug(0)`` enables all available OS debug log messages (in the
+    default build configuration this is ``LOG_INFO``).
+
+    ``osdebug(0, level)`` sets the OS debug log message level to the
+     specified value. The log levels are defined as constants:
 
         * ``LOG_NONE`` -- No log output
         * ``LOG_ERROR`` -- Critical errors, software module can not recover on its own
@@ -77,6 +100,15 @@ Functions
         * ``LOG_VERBOSE`` -- Bigger chunks of debugging information, or frequent messages
           which can potentially flood the output
 
+    .. note:: ``LOG_DEBUG`` and ``LOG_VERBOSE`` are not compiled into the
+              MicroPython binary by default, to save size. A custom build with a
+              modified "``sdkconfig``" source file is needed to see any output
+              at these log levels.
+
+    .. note:: Log output on ESP32 is automatically suspended in "Raw REPL" mode,
+              to prevent communications issues. This means OS level logging is never
+              seen when using ``mpremote run`` and similar tools.
+
 .. function:: set_native_code_location(start, length)
 
     **Note**: ESP8266 only
diff --git a/examples/usercmodule/cppexample/example.cpp b/examples/usercmodule/cppexample/example.cpp
index 06809732a4d7..2df832baa76f 100644
--- a/examples/usercmodule/cppexample/example.cpp
+++ b/examples/usercmodule/cppexample/example.cpp
@@ -1,9 +1,16 @@
 extern "C" {
 #include <examplemodule.h>
+#include <py/objstr.h>
 
 // Here we implement the function using C++ code, but since it's
 // declaration has to be compatible with C everything goes in extern "C" scope.
 mp_obj_t cppfunc(mp_obj_t a_obj, mp_obj_t b_obj) {
+    // The following no-ops are just here to verify the static assertions used in
+    // the public API all compile with C++.
+    MP_STATIC_ASSERT_STR_ARRAY_COMPATIBLE;
+    if (mp_obj_is_type(a_obj, &mp_type_BaseException)) {
+    }
+
     // Prove we have (at least) C++11 features.
     const auto a = mp_obj_get_int(a_obj);
     const auto b = mp_obj_get_int(b_obj);
diff --git a/extmod/extmod.mk b/extmod/extmod.mk
index a04856bce205..84573ec86106 100644
--- a/extmod/extmod.mk
+++ b/extmod/extmod.mk
@@ -267,6 +267,9 @@ SRC_THIRDPARTY_C += $(addprefix $(LWIP_DIR)/,\
 	core/ipv6/nd6.c \
 	netif/ethernet.c \
 	)
+ifeq ($(MICROPY_PY_LWIP_LOOPBACK),1)
+CFLAGS_EXTMOD += -DLWIP_NETIF_LOOPBACK=1
+endif
 ifeq ($(MICROPY_PY_LWIP_SLIP),1)
 CFLAGS_EXTMOD += -DMICROPY_PY_LWIP_SLIP=1
 SRC_THIRDPARTY_C += $(LWIP_DIR)/netif/slipif.c
diff --git a/ports/esp32/boards/ARDUINO_NANO_ESP32/mpconfigboard.h b/ports/esp32/boards/ARDUINO_NANO_ESP32/mpconfigboard.h
index 3e98bb99d702..ec85a7bb3692 100644
--- a/ports/esp32/boards/ARDUINO_NANO_ESP32/mpconfigboard.h
+++ b/ports/esp32/boards/ARDUINO_NANO_ESP32/mpconfigboard.h
@@ -1,6 +1,9 @@
 #define MICROPY_HW_BOARD_NAME               "Arduino Nano ESP32"
 #define MICROPY_HW_MCU_NAME                 "ESP32S3"
 
+// Network config
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "mpy-nano-esp32"
+
 #define MICROPY_PY_MACHINE_DAC              (0)
 
 #define MICROPY_HW_I2C0_SCL                 (12)
diff --git a/ports/esp32/boards/ESP32_GENERIC/sdkconfig.d2wd b/ports/esp32/boards/ESP32_GENERIC/sdkconfig.d2wd
index f6e07893e937..2ac983693d3f 100644
--- a/ports/esp32/boards/ESP32_GENERIC/sdkconfig.d2wd
+++ b/ports/esp32/boards/ESP32_GENERIC/sdkconfig.d2wd
@@ -3,6 +3,10 @@ CONFIG_COMPILER_OPTIMIZATION_SIZE=y
 CONFIG_COMPILER_OPTIMIZATION_PERF=n
 CONFIG_COMPILER_OPTIMIZATION_CHECKS_SILENT=y
 
+# Change maximum log level to error, to reduce firmware size.
+CONFIG_LOG_MAXIMUM_LEVEL_ERROR=y
+CONFIG_LOG_MAXIMUM_LEVEL_INFO=n
+
 # Disable SPI Ethernet driver to reduce firmware size.
 CONFIG_ETH_USE_SPI_ETHERNET=n
 
diff --git a/ports/esp32/boards/sdkconfig.base b/ports/esp32/boards/sdkconfig.base
index 372633e711a6..2a7c9a1c5b8c 100644
--- a/ports/esp32/boards/sdkconfig.base
+++ b/ports/esp32/boards/sdkconfig.base
@@ -17,9 +17,18 @@ CONFIG_BOOTLOADER_SKIP_VALIDATE_IN_DEEP_SLEEP=y
 CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE=y
 
 # Change default log level to "ERROR" (instead of "INFO")
-CONFIG_LOG_DEFAULT_LEVEL_INFO=n
 CONFIG_LOG_DEFAULT_LEVEL_ERROR=y
-CONFIG_LOG_DEFAULT_LEVEL=1
+
+# Set the maximum included log level higher than the default,
+# so esp.osdebug() can enable more logging at runtime.
+#
+# To increase the max log verbosity to Debug or Verbose instead, comment
+# CONFIG_LOG_MAXIMUM_LEVEL_INFO=y and uncomment one of the other settings.
+#
+# If not needed, the next line can be commented entirely to save binary size.
+CONFIG_LOG_MAXIMUM_LEVEL_INFO=y
+#CONFIG_LOG_MAXIMUM_LEVEL_DEBUG=y
+#CONFIG_LOG_MAXIMUM_LEVEL_VERBOSE=y
 
 # Main XTAL Config
 # Only on: ESP32
diff --git a/ports/esp32/esp32_rmt.c b/ports/esp32/esp32_rmt.c
index 5d53018f4ba1..77a31ebc0f66 100644
--- a/ports/esp32/esp32_rmt.c
+++ b/ports/esp32/esp32_rmt.c
@@ -323,12 +323,18 @@ STATIC mp_obj_t esp32_rmt_write_pulses(size_t n_args, const mp_obj_t *args) {
         check_esp_err(rmt_wait_tx_done(self->channel_id, portMAX_DELAY));
     }
 
+    #if !CONFIG_IDF_TARGET_ESP32S3
+    check_esp_err(rmt_write_items(self->channel_id, self->items, num_items, false));
+    #endif
+
     if (self->loop_en) {
         check_esp_err(rmt_set_tx_intr_en(self->channel_id, false));
         check_esp_err(rmt_set_tx_loop_mode(self->channel_id, true));
     }
 
+    #if CONFIG_IDF_TARGET_ESP32S3
     check_esp_err(rmt_write_items(self->channel_id, self->items, num_items, false));
+    #endif
 
     return mp_const_none;
 }
diff --git a/ports/esp32/modesp.c b/ports/esp32/modesp.c
index 4726ce587420..f51ba6ab34d5 100644
--- a/ports/esp32/modesp.c
+++ b/ports/esp32/modesp.c
@@ -37,12 +37,12 @@
 #include "py/mphal.h"
 
 STATIC mp_obj_t esp_osdebug(size_t n_args, const mp_obj_t *args) {
-    esp_log_level_t level = LOG_LOCAL_LEVEL;
+    esp_log_level_t level = LOG_LOCAL_LEVEL; // Maximum available level
     if (n_args == 2) {
         level = mp_obj_get_int(args[1]);
     }
     if (args[0] == mp_const_none) {
-        // Disable logging
+        // Set logging back to boot default of ESP_LOG_ERROR
         esp_log_level_set("*", ESP_LOG_ERROR);
     } else {
         // Enable logging at the given level
diff --git a/ports/esp32/modsocket.c b/ports/esp32/modsocket.c
index cacc52dec568..ca8c63030cd7 100644
--- a/ports/esp32/modsocket.c
+++ b/ports/esp32/modsocket.c
@@ -36,6 +36,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "py/gc.h"
 #include "py/runtime0.h"
 #include "py/nlr.h"
 #include "py/objlist.h"
@@ -274,6 +275,13 @@ STATIC mp_obj_t socket_make_new(const mp_obj_type_t *type_in, size_t n_args, siz
     sock->state = sock->type == SOCK_STREAM ? SOCKET_STATE_NEW : SOCKET_STATE_CONNECTED;
 
     sock->fd = lwip_socket(sock->domain, sock->type, sock->proto);
+    if (sock->fd < 0 && errno == ENFILE) {
+        // ESP32 LWIP has a hard socket limit, ENFILE is returned when this is
+        // reached. Similar to the logic elsewhere for MemoryError, try running
+        // GC before failing outright.
+        gc_collect();
+        sock->fd = lwip_socket(sock->domain, sock->type, sock->proto);
+    }
     if (sock->fd < 0) {
         mp_raise_OSError(errno);
     }
diff --git a/ports/esp32/network_wlan.c b/ports/esp32/network_wlan.c
index 74c6e8f9303d..e8c75c619df6 100644
--- a/ports/esp32/network_wlan.c
+++ b/ports/esp32/network_wlan.c
@@ -41,6 +41,7 @@
 
 #include "esp_wifi.h"
 #include "esp_log.h"
+#include "esp_psram.h"
 
 #ifndef NO_QSTR
 #include "mdns.h"
@@ -206,6 +207,23 @@ void esp_initialise_wifi(void) {
         wlan_ap_obj.active = false;
 
         wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
+        #if CONFIG_SPIRAM_IGNORE_NOTFOUND
+        if (!esp_psram_is_initialized()) {
+            // If PSRAM failed to initialize, disable "Wi-Fi Cache TX Buffers"
+            // (default SPIRAM config ESP32_WIFI_CACHE_TX_BUFFER_NUM==32, this is 54,400 bytes of heap)
+            cfg.cache_tx_buf_num = 0;
+            cfg.feature_caps &= ~CONFIG_FEATURE_CACHE_TX_BUF_BIT;
+
+            // Set some other options back to the non-SPIRAM default values
+            // to save more RAM.
+            //
+            // These can be determined from ESP-IDF components/esp_wifi/Kconfig and the
+            // WIFI_INIT_CONFIG_DEFAULT macro
+            cfg.tx_buf_type = 1; // Dynamic, this "magic number" is defined in IDF KConfig
+            cfg.static_tx_buf_num = 0; // Probably don't need, due to tx_buf_type
+            cfg.dynamic_tx_buf_num = 32; // ESP-IDF default value (maximum)
+        }
+        #endif
         ESP_LOGD("modnetwork", "Initializing WiFi");
         esp_exceptions(esp_wifi_init(&cfg));
         esp_exceptions(esp_wifi_set_storage(WIFI_STORAGE_RAM));
diff --git a/ports/esp32/uart.c b/ports/esp32/uart.c
index fc69e279e33d..b82a638a5b27 100644
--- a/ports/esp32/uart.c
+++ b/ports/esp32/uart.c
@@ -34,12 +34,9 @@
 #if MICROPY_HW_ENABLE_UART_REPL
 
 #include <stdio.h>
+#include "driver/uart.h" // For uart_get_sclk_freq()
 #include "hal/uart_hal.h"
 
-// Backwards compatibility for when MICROPY_HW_UART_REPL was a ESP-IDF UART
-// driver enum. Only UART_NUM_0 was supported with that version of the driver.
-#define UART_NUM_0 0
-
 STATIC void uart_irq_handler(void *arg);
 
 // Declaring the HAL structure on the stack saves a tiny amount of static RAM
@@ -53,16 +50,18 @@ STATIC void uart_irq_handler(void *arg);
 
 void uart_stdout_init(void) {
     uart_hal_context_t repl_hal = REPL_HAL_DEFN();
-    uint32_t sclk_freq;
-
-    #if UART_SCLK_DEFAULT == SOC_MOD_CLK_APB
-    sclk_freq = APB_CLK_FREQ; // Assumes no frequency scaling
+    #if ESP_IDF_VERSION < ESP_IDF_VERSION_VAL(5, 3, 0)
+    uart_sclk_t sclk;
     #else
-    // ESP32-H2 and ESP32-C2, I think
-    #error "This SoC uses a different default UART SCLK source, code needs updating."
+    soc_module_clk_t sclk;
     #endif
+    uint32_t sclk_freq;
+
+    uart_hal_get_sclk(&repl_hal, &sclk); // To restore SCLK after uart_hal_init() resets it
+    ESP_ERROR_CHECK(uart_get_sclk_freq(sclk, &sclk_freq));
 
     uart_hal_init(&repl_hal, MICROPY_HW_UART_REPL); // Sets defaults: 8n1, no flow control
+    uart_hal_set_sclk(&repl_hal, sclk);
     uart_hal_set_baudrate(&repl_hal, MICROPY_HW_UART_REPL_BAUD, sclk_freq);
     uart_hal_rxfifo_rst(&repl_hal);
     uart_hal_txfifo_rst(&repl_hal);
diff --git a/ports/renesas-ra/boards/ARDUINO_PORTENTA_C33/mpconfigboard.h b/ports/renesas-ra/boards/ARDUINO_PORTENTA_C33/mpconfigboard.h
index aa1e28ab9d09..52346dedc44e 100644
--- a/ports/renesas-ra/boards/ARDUINO_PORTENTA_C33/mpconfigboard.h
+++ b/ports/renesas-ra/boards/ARDUINO_PORTENTA_C33/mpconfigboard.h
@@ -5,10 +5,14 @@
  */
 
 // MCU config
-#define MICROPY_HW_BOARD_NAME       "PORTENTA C33"
+#define MICROPY_HW_BOARD_NAME       "Arduino Portenta C33"
 #define MICROPY_HW_MCU_NAME         "RA6M5"
 #define MICROPY_HW_MCU_SYSCLK       200000000
 #define MICROPY_HW_MCU_PCLK         100000000
+#define MICROPY_HW_FLASH_FS_LABEL   "Portenta C33"
+
+// Network config
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "mpy-portenta-c33"
 
 // module config
 #define MICROPY_EMIT_THUMB          (1)
@@ -59,8 +63,8 @@ void PORTENTA_C33_board_enter_bootloader(void);
 #endif
 
 // I2C
-#define MICROPY_HW_I2C2_SCL         (pin_P407)
-#define MICROPY_HW_I2C2_SDA         (pin_P408)
+#define MICROPY_HW_I2C0_SCL         (pin_P408)
+#define MICROPY_HW_I2C0_SDA         (pin_P407)
 
 // SPI
 #define MICROPY_HW_SPI1_SSL         (pin_P104)
diff --git a/ports/renesas-ra/mphalport.h b/ports/renesas-ra/mphalport.h
index 2b25a36fbf85..e29a7fec7b81 100644
--- a/ports/renesas-ra/mphalport.h
+++ b/ports/renesas-ra/mphalport.h
@@ -29,6 +29,9 @@
 #include "pin.h"
 #include "py/ringbuf.h"
 
+#define MICROPY_PY_PENDSV_ENTER   uint32_t atomic_state = raise_irq_pri(IRQ_PRI_PENDSV)
+#define MICROPY_PY_PENDSV_EXIT    restore_irq_pri(atomic_state)
+
 #define MICROPY_HW_USB_CDC_TX_TIMEOUT (500)
 
 extern const unsigned char mp_hal_status_to_errno_table[4];
diff --git a/ports/renesas-ra/usbd.c b/ports/renesas-ra/usbd.c
index 7047503864f6..e7252b5f7acf 100644
--- a/ports/renesas-ra/usbd.c
+++ b/ports/renesas-ra/usbd.c
@@ -34,15 +34,8 @@
 
 void mp_usbd_port_get_serial_number(char *serial_buf) {
     const bsp_unique_id_t *id = R_BSP_UniqueIdGet();
-    // convert to hex
-    int hexlen = sizeof(id->unique_id_bytes) * 2;
-    MP_STATIC_ASSERT(hexlen <= MICROPY_HW_USB_DESC_STR_MAX);
-    for (int i = 0; i < hexlen; i += 2) {
-        static const char *hexdig = "0123456789abcdef";
-        serial_buf[i] = hexdig[id->unique_id_bytes[i / 2] >> 4];
-        serial_buf[i + 1] = hexdig[id->unique_id_bytes[i / 2] & 0x0f];
-    }
-    serial_buf[hexlen] = 0;
+    MP_STATIC_ASSERT(sizeof(id->unique_id_bytes) * 2 <= MICROPY_HW_USB_DESC_STR_MAX);
+    mp_usbd_hex_str(serial_buf, id->unique_id_bytes, sizeof(id->unique_id_bytes));
 }
 
 #endif
diff --git a/ports/rp2/CMakeLists.txt b/ports/rp2/CMakeLists.txt
index 15f6f6ca1c28..0f8c6d8e88a9 100644
--- a/ports/rp2/CMakeLists.txt
+++ b/ports/rp2/CMakeLists.txt
@@ -102,6 +102,7 @@ set(MICROPY_SOURCE_LIB
     ${MICROPY_DIR}/shared/runtime/mpirq.c
     ${MICROPY_DIR}/shared/runtime/pyexec.c
     ${MICROPY_DIR}/shared/runtime/stdout_helpers.c
+    ${MICROPY_DIR}/shared/runtime/softtimer.c
     ${MICROPY_DIR}/shared/runtime/sys_stdio_mphal.c
     ${MICROPY_DIR}/shared/timeutils/timeutils.c
     ${MICROPY_DIR}/shared/tinyusb/mp_cdc_common.c
diff --git a/ports/rp2/boards/ARDUINO_NANO_RP2040_CONNECT/mpconfigboard.h b/ports/rp2/boards/ARDUINO_NANO_RP2040_CONNECT/mpconfigboard.h
index 537c6d705705..b969341a7fe1 100644
--- a/ports/rp2/boards/ARDUINO_NANO_RP2040_CONNECT/mpconfigboard.h
+++ b/ports/rp2/boards/ARDUINO_NANO_RP2040_CONNECT/mpconfigboard.h
@@ -4,6 +4,9 @@
 #define MICROPY_HW_BOARD_NAME           "Arduino Nano RP2040 Connect"
 #define MICROPY_HW_FLASH_STORAGE_BYTES  (8 * 1024 * 1024)
 
+// Network config
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "mpy-nano-rp2040-connect"
+
 // Enable networking.
 #define MICROPY_PY_NETWORK              (1)
 
diff --git a/ports/rp2/cyw43_configport.h b/ports/rp2/cyw43_configport.h
index 8f64762df561..96324ee5ec96 100644
--- a/ports/rp2/cyw43_configport.h
+++ b/ports/rp2/cyw43_configport.h
@@ -104,11 +104,9 @@ void cyw43_post_poll_hook(void);
 extern volatile int cyw43_has_pending;
 
 static inline void cyw43_yield(void) {
-    uint32_t my_interrupts = save_and_disable_interrupts();
     if (!cyw43_has_pending) {
-        __WFI();
+        best_effort_wfe_or_timeout(make_timeout_time_ms(1));
     }
-    restore_interrupts(my_interrupts);
 }
 
 static inline void cyw43_delay_us(uint32_t us) {
@@ -118,12 +116,7 @@ static inline void cyw43_delay_us(uint32_t us) {
 }
 
 static inline void cyw43_delay_ms(uint32_t ms) {
-    uint32_t us = ms * 1000;
-    int32_t start = mp_hal_ticks_us();
-    while (mp_hal_ticks_us() - start < us) {
-        cyw43_yield();
-        MICROPY_EVENT_POLL_HOOK_FAST;
-    }
+    mp_hal_delay_ms(ms);
 }
 
 #define CYW43_EVENT_POLL_HOOK MICROPY_EVENT_POLL_HOOK_FAST
diff --git a/ports/rp2/main.c b/ports/rp2/main.c
index 682ea14476aa..43680a46cd68 100644
--- a/ports/rp2/main.c
+++ b/ports/rp2/main.c
@@ -37,6 +37,7 @@
 #include "shared/readline/readline.h"
 #include "shared/runtime/gchelper.h"
 #include "shared/runtime/pyexec.h"
+#include "shared/runtime/softtimer.h"
 #include "tusb.h"
 #include "uart.h"
 #include "modmachine.h"
@@ -212,6 +213,7 @@ int main(int argc, char **argv) {
         #if MICROPY_PY_THREAD
         mp_thread_deinit();
         #endif
+        soft_timer_deinit();
         gc_sweep_all();
         mp_deinit();
     }
diff --git a/ports/rp2/mpbthciport.c b/ports/rp2/mpbthciport.c
index 16d50ddacc3a..1aacbe881f9f 100644
--- a/ports/rp2/mpbthciport.c
+++ b/ports/rp2/mpbthciport.c
@@ -30,36 +30,37 @@
 #include "extmod/modbluetooth.h"
 #include "extmod/modmachine.h"
 #include "extmod/mpbthci.h"
+#include "shared/runtime/softtimer.h"
 #include "modmachine.h"
 #include "mpbthciport.h"
-#include "pico/stdlib.h"
 
 #if MICROPY_PY_BLUETOOTH
 
 #define debug_printf(...) // mp_printf(&mp_plat_print, "mpbthciport.c: " __VA_ARGS__)
 #define error_printf(...) mp_printf(&mp_plat_print, "mpbthciport.c: " __VA_ARGS__)
 
-// Poll timer ID.
-static alarm_id_t poll_timer_id = 0;
-
 uint8_t mp_bluetooth_hci_cmd_buf[4 + 256];
 
+// Soft timer and scheduling node for scheduling a HCI poll.
+static soft_timer_entry_t mp_bluetooth_hci_soft_timer;
 static mp_sched_node_t mp_bluetooth_hci_sched_node;
 
-void mp_bluetooth_hci_init(void) {
+// This is called by soft_timer and executes at PendSV level.
+static void mp_bluetooth_hci_soft_timer_callback(soft_timer_entry_t *self) {
+    mp_bluetooth_hci_poll_now();
 }
 
-static int64_t mp_bluetooth_hci_timer_callback(alarm_id_t id, void *user_data) {
-    poll_timer_id = 0;
-    mp_bluetooth_hci_poll_now();
-    return 0;
+void mp_bluetooth_hci_init(void) {
+    soft_timer_static_init(
+        &mp_bluetooth_hci_soft_timer,
+        SOFT_TIMER_MODE_ONE_SHOT,
+        0,
+        mp_bluetooth_hci_soft_timer_callback
+        );
 }
 
 void mp_bluetooth_hci_poll_in_ms(uint32_t ms) {
-    if (poll_timer_id != 0) {
-        cancel_alarm(poll_timer_id);
-    }
-    poll_timer_id = add_alarm_in_ms(ms, mp_bluetooth_hci_timer_callback, NULL, true);
+    soft_timer_reinsert(&mp_bluetooth_hci_soft_timer, ms);
 }
 
 // For synchronous mode, we run all BLE stack code inside a scheduled task.
@@ -110,10 +111,8 @@ int mp_bluetooth_hci_uart_deinit(void) {
     debug_printf("mp_bluetooth_hci_uart_deinit\n");
 
     // If a poll callback is set cancel it now.
-    if (poll_timer_id > 0) {
-        cancel_alarm(poll_timer_id);
-    }
-    poll_timer_id = 0;
+    soft_timer_remove(&mp_bluetooth_hci_soft_timer);
+
     return 0;
 }
 
diff --git a/ports/rp2/mphalport.c b/ports/rp2/mphalport.c
index 4b1c1fa1f5bf..1fb833f2e5dc 100644
--- a/ports/rp2/mphalport.c
+++ b/ports/rp2/mphalport.c
@@ -29,8 +29,10 @@
 #include "py/mphal.h"
 #include "extmod/misc.h"
 #include "shared/runtime/interrupt_char.h"
+#include "shared/runtime/softtimer.h"
 #include "shared/timeutils/timeutils.h"
 #include "shared/tinyusb/mp_usbd.h"
+#include "pendsv.h"
 #include "tusb.h"
 #include "uart.h"
 #include "hardware/rtc.h"
@@ -44,6 +46,8 @@
 // microseconds since the Epoch.
 STATIC uint64_t time_us_64_offset_from_epoch;
 
+static alarm_id_t soft_timer_alarm_id = 0;
+
 #if MICROPY_HW_ENABLE_UART_REPL || MICROPY_HW_USB_CDC
 
 #ifndef MICROPY_HW_STDIN_BUFFER_LEN
@@ -188,10 +192,9 @@ void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
 
 void mp_hal_delay_ms(mp_uint_t ms) {
     absolute_time_t t = make_timeout_time_ms(ms);
-    while (!time_reached(t)) {
+    do {
         MICROPY_EVENT_POLL_HOOK_FAST;
-        best_effort_wfe_or_timeout(t);
-    }
+    } while (!best_effort_wfe_or_timeout(t));
 }
 
 void mp_hal_time_ns_set_from_rtc(void) {
@@ -260,3 +263,22 @@ void mp_hal_get_mac_ascii(int idx, size_t chr_off, size_t chr_len, char *dest) {
 uint32_t storage_read_blocks(uint8_t *dest, uint32_t block_num, uint32_t num_blocks) {
     panic_unsupported();
 }
+
+static int64_t soft_timer_callback(alarm_id_t id, void *user_data) {
+    soft_timer_alarm_id = 0;
+    pendsv_schedule_dispatch(PENDSV_DISPATCH_SOFT_TIMER, soft_timer_handler);
+    return 0; // don't reschedule this alarm
+}
+
+uint32_t soft_timer_get_ms(void) {
+    return mp_hal_ticks_ms();
+}
+
+void soft_timer_schedule_at_ms(uint32_t ticks_ms) {
+    if (soft_timer_alarm_id != 0) {
+        cancel_alarm(soft_timer_alarm_id);
+    }
+    int32_t ms = soft_timer_ticks_diff(ticks_ms, mp_hal_ticks_ms());
+    ms = MAX(0, ms);
+    soft_timer_alarm_id = add_alarm_in_ms(ms, soft_timer_callback, NULL, true);
+}
diff --git a/ports/rp2/mphalport.h b/ports/rp2/mphalport.h
index 95e7cba2c542..b8133c783e28 100644
--- a/ports/rp2/mphalport.h
+++ b/ports/rp2/mphalport.h
@@ -31,10 +31,14 @@
 #include "hardware/clocks.h"
 #include "hardware/structs/systick.h"
 #include "RP2040.h" // cmsis, for __WFI
+#include "pendsv.h"
 
 #define SYSTICK_MAX (0xffffff)
 #define MICROPY_HW_USB_CDC_TX_TIMEOUT (500)
 
+#define MICROPY_PY_PENDSV_ENTER   pendsv_suspend()
+#define MICROPY_PY_PENDSV_EXIT    pendsv_resume()
+
 extern int mp_interrupt_char;
 extern ringbuf_t stdin_ringbuf;
 
diff --git a/ports/rp2/mpnetworkport.c b/ports/rp2/mpnetworkport.c
index dac04760b846..09a543c2db34 100644
--- a/ports/rp2/mpnetworkport.c
+++ b/ports/rp2/mpnetworkport.c
@@ -30,13 +30,14 @@
 
 #if MICROPY_PY_LWIP
 
+#include "shared/runtime/softtimer.h"
 #include "lwip/timeouts.h"
-#include "pico/time.h"
 
 // Poll lwIP every 64ms by default
 #define LWIP_TICK_RATE_MS 64
 
-static alarm_id_t lwip_alarm_id = -1;
+// Soft timer for running lwIP in the background.
+static soft_timer_entry_t mp_network_soft_timer;
 
 #if MICROPY_PY_NETWORK_CYW43
 #include "lib/cyw43-driver/src/cyw43.h"
@@ -56,6 +57,7 @@ static void gpio_irq_handler(void) {
         // CYW43_POST_POLL_HOOK which is called at the end of cyw43_poll_func.
         gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, CYW43_IRQ_LEVEL, false);
         cyw43_has_pending = 1;
+        __SEV();
         pendsv_schedule_dispatch(PENDSV_DISPATCH_CYW43, cyw43_poll);
         CYW43_STAT_INC(IRQ_COUNT);
     }
@@ -88,11 +90,6 @@ u32_t sys_now(void) {
     return mp_hal_ticks_ms();
 }
 
-STATIC void lwip_poll(void) {
-    // Run the lwIP internal updates
-    sys_check_timeouts();
-}
-
 void lwip_lock_acquire(void) {
     // Prevent PendSV from running.
     pendsv_suspend();
@@ -103,22 +100,25 @@ void lwip_lock_release(void) {
     pendsv_resume();
 }
 
-STATIC int64_t alarm_callback(alarm_id_t id, void *user_data) {
-    pendsv_schedule_dispatch(PENDSV_DISPATCH_LWIP, lwip_poll);
+// This is called by soft_timer and executes at PendSV level.
+static void mp_network_soft_timer_callback(soft_timer_entry_t *self) {
+    // Run the lwIP internal updates.
+    sys_check_timeouts();
+
     #if MICROPY_PY_NETWORK_WIZNET5K
-    pendsv_schedule_dispatch(PENDSV_DISPATCH_WIZNET, wiznet5k_poll);
+    wiznet5k_poll();
     #endif
-    return LWIP_TICK_RATE_MS * 1000;
 }
 
 void mod_network_lwip_init(void) {
-    #if MICROPY_PY_NETWORK_WIZNET5K
-    wiznet5k_deinit();
-    #endif
-    if (lwip_alarm_id != -1) {
-        cancel_alarm(lwip_alarm_id);
-    }
-    lwip_alarm_id = add_alarm_in_us(LWIP_TICK_RATE_MS * 1000, alarm_callback, mp_const_true, true);
+    soft_timer_static_init(
+        &mp_network_soft_timer,
+        SOFT_TIMER_MODE_PERIODIC,
+        LWIP_TICK_RATE_MS,
+        mp_network_soft_timer_callback
+        );
+
+    soft_timer_reinsert(&mp_network_soft_timer, LWIP_TICK_RATE_MS);
 }
 
 #endif // MICROPY_PY_LWIP
diff --git a/ports/rp2/mpnimbleport.c b/ports/rp2/mpnimbleport.c
index 74e9ecb02602..fbeaf2beca80 100644
--- a/ports/rp2/mpnimbleport.c
+++ b/ports/rp2/mpnimbleport.c
@@ -69,9 +69,8 @@ void mp_bluetooth_hci_poll(void) {
 // --- Port-specific helpers for the generic NimBLE bindings. -----------------
 
 void mp_bluetooth_nimble_hci_uart_wfi(void) {
-    #if defined(__WFI)
-    __WFI();
-    #endif
+    best_effort_wfe_or_timeout(make_timeout_time_ms(1));
+
     // This is called while NimBLE is waiting in ble_npl_sem_pend, i.e. waiting for an HCI ACK.
     // Do not need to run events here (it must not invoke Python code), only processing incoming HCI data.
     mp_bluetooth_nimble_hci_uart_process(false);
diff --git a/ports/rp2/pendsv.h b/ports/rp2/pendsv.h
index 294cef3c70b6..bc8e8d61c8c0 100644
--- a/ports/rp2/pendsv.h
+++ b/ports/rp2/pendsv.h
@@ -29,9 +29,7 @@
 #include <stddef.h>
 
 enum {
-    #if MICROPY_PY_LWIP
-    PENDSV_DISPATCH_LWIP,
-    #endif
+    PENDSV_DISPATCH_SOFT_TIMER,
     #if MICROPY_PY_NETWORK_CYW43
     PENDSV_DISPATCH_CYW43,
     #endif
diff --git a/ports/rp2/usbd.c b/ports/rp2/usbd.c
index 568b6284169b..8724f802f074 100644
--- a/ports/rp2/usbd.c
+++ b/ports/rp2/usbd.c
@@ -36,15 +36,8 @@
 void mp_usbd_port_get_serial_number(char *serial_buf) {
     pico_unique_board_id_t id;
     pico_get_unique_board_id(&id);
-    // convert to hex
-    int hexlen = sizeof(id.id) * 2;
-    MP_STATIC_ASSERT(hexlen <= MICROPY_HW_USB_DESC_STR_MAX);
-    for (int i = 0; i < hexlen; i += 2) {
-        static const char *hexdig = "0123456789abcdef";
-        serial_buf[i] = hexdig[id.id[i / 2] >> 4];
-        serial_buf[i + 1] = hexdig[id.id[i / 2] & 0x0f];
-    }
-    serial_buf[hexlen] = 0;
+    MP_STATIC_ASSERT(sizeof(id.id) * 2 <= MICROPY_HW_USB_DESC_STR_MAX);
+    mp_usbd_hex_str(serial_buf, id.id, sizeof(id.id));
 }
 
 #endif
diff --git a/ports/samd/Makefile b/ports/samd/Makefile
index 12223e6ded8f..95d0f3bd18f4 100644
--- a/ports/samd/Makefile
+++ b/ports/samd/Makefile
@@ -55,6 +55,7 @@ INC += -I$(TOP)/lib/asf4/$(MCU_SERIES_LOWER)/hpl/tc
 INC += -I$(TOP)/lib/asf4/$(MCU_SERIES_LOWER)/include
 INC += -I$(TOP)/lib/asf4/$(MCU_SERIES_LOWER)/include/pio
 INC += -I$(TOP)/lib/tinyusb/src
+INC += -I$(TOP)/shared/tinyusb/
 
 MAKE_PINS = boards/make-pins.py
 BOARD_PINS = $(BOARD_DIR)/pins.csv
@@ -117,7 +118,7 @@ SRC_C += \
 	samd_qspiflash.c \
 	samd_soc.c \
 	samd_spiflash.c \
-	tusb_port.c \
+	usbd.c \
 
 SHARED_SRC_C += \
 	drivers/dht/dht.c \
@@ -133,7 +134,8 @@ SHARED_SRC_C += \
 	shared/runtime/sys_stdio_mphal.c \
 	shared/timeutils/timeutils.c \
 	shared/tinyusb/mp_cdc_common.c \
-	shared/tinyusb/mp_usbd.c
+	shared/tinyusb/mp_usbd.c \
+	shared/tinyusb/mp_usbd_descriptor.c \
 
 ASF4_SRC_C += $(addprefix lib/asf4/$(MCU_SERIES_LOWER)/,\
 	hal/src/hal_atomic.c \
diff --git a/ports/samd/mcu/samd21/mpconfigmcu.mk b/ports/samd/mcu/samd21/mpconfigmcu.mk
index 35f442d86990..b3092837cbd1 100644
--- a/ports/samd/mcu/samd21/mpconfigmcu.mk
+++ b/ports/samd/mcu/samd21/mpconfigmcu.mk
@@ -1,5 +1,7 @@
 CFLAGS_MCU += -mtune=cortex-m0plus -mcpu=cortex-m0plus -msoft-float
 
+CFLAGS_MCU += -DCFG_TUSB_MCU=OPT_MCU_SAMD21
+
 MPY_CROSS_MCU_ARCH = armv6m
 
 MICROPY_HW_CODESIZE ?= 184K
diff --git a/ports/samd/mcu/samd51/mpconfigmcu.mk b/ports/samd/mcu/samd51/mpconfigmcu.mk
index c706331aca45..0201bacffeef 100644
--- a/ports/samd/mcu/samd51/mpconfigmcu.mk
+++ b/ports/samd/mcu/samd51/mpconfigmcu.mk
@@ -1,5 +1,7 @@
 CFLAGS_MCU += -mtune=cortex-m4 -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard
 
+CFLAGS_MCU += -DCFG_TUSB_MCU=OPT_MCU_SAMD51
+
 MPY_CROSS_MCU_ARCH = armv7m
 
 MICROPY_HW_CODESIZE ?= 368K
diff --git a/ports/samd/modmachine.c b/ports/samd/modmachine.c
index 7c3d96eb0136..8c4808075e7a 100644
--- a/ports/samd/modmachine.c
+++ b/ports/samd/modmachine.c
@@ -92,45 +92,9 @@ STATIC mp_obj_t machine_freq(size_t n_args, const mp_obj_t *args) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_freq_obj, 0, 1, machine_freq);
 
 STATIC mp_obj_t machine_unique_id(void) {
-    // Each device has a unique 128-bit serial number which is a concatenation of four 32-bit
-    // words contained at the following addresses. The uniqueness of the serial number is
-    // guaranteed only when using all 128 bits.
-    // Atmel SAM D21E / SAM D21G / SAM D21J
-    // SMART ARM-Based Microcontroller
-    // DATASHEET
-    // 9.6 (SAMD51) or 9.3.3 (or 10.3.3 depending on which manual)(SAMD21) Serial Number
-    //
-    // EXAMPLE (SAMD21)
-    // ----------------
-    // OpenOCD:
-    // Word0:
-    // > at91samd21g18.cpu mdw 0x0080A00C 1
-    // 0x0080a00c: 6e27f15f
-    // Words 1-3:
-    // > at91samd21g18.cpu mdw 0x0080A040 3
-    // 0x0080a040: 50534b54 332e3120 ff091645
-    //
-    // MicroPython (this code and same order as shown in Arduino IDE)
-    // >>> binascii.hexlify(machine.unique_id())
-    // b'6e27f15f50534b54332e3120ff091645'
-
-    #if defined(MCU_SAMD21)
-    uint32_t *id_addresses[4] = {(uint32_t *)0x0080A00C, (uint32_t *)0x0080A040,
-                                 (uint32_t *)0x0080A044, (uint32_t *)0x0080A048};
-    #elif defined(MCU_SAMD51)
-    uint32_t *id_addresses[4] = {(uint32_t *)0x008061FC, (uint32_t *)0x00806010,
-                                 (uint32_t *)0x00806014, (uint32_t *)0x00806018};
-    #endif
-    uint8_t raw_id[16];
-
-    for (int i = 0; i < 4; i++) {
-        for (int k = 0; k < 4; k++) {
-            // 'Reverse' the read bytes into a 32 bit word (Consistent with Arduino)
-            raw_id[4 * i + k] = (*(id_addresses[i]) >> (24 - k * 8)) & 0xff;
-        }
-    }
-
-    return mp_obj_new_bytes((byte *)&raw_id, sizeof(raw_id));
+    samd_unique_id_t id;
+    samd_get_unique_id(&id);
+    return mp_obj_new_bytes((byte *)&id.bytes, sizeof(id.bytes));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(machine_unique_id_obj, machine_unique_id);
 
diff --git a/ports/samd/mpconfigport.h b/ports/samd/mpconfigport.h
index 91a7c1a10d87..3684457b48e0 100644
--- a/ports/samd/mpconfigport.h
+++ b/ports/samd/mpconfigport.h
@@ -62,6 +62,18 @@
 #define MICROPY_HW_ENABLE_USBDEV            (1)
 #define MICROPY_HW_USB_CDC_1200BPS_TOUCH    (1)
 
+#if MICROPY_HW_ENABLE_USBDEV
+// Enable USB-CDC serial port
+#ifndef MICROPY_HW_USB_CDC
+#define MICROPY_HW_USB_CDC (1)
+#endif
+// SAMD unique ID is 16 bytes (hex string == 32)
+#ifndef MICROPY_HW_USB_DESC_STR_MAX
+#define MICROPY_HW_USB_DESC_STR_MAX (32)
+#endif
+
+#endif
+
 // Control over Python builtins
 #define MICROPY_PY_BUILTINS_BYTES_HEX       (1)
 #define MICROPY_PY_BUILTINS_MEMORYVIEW      (1)
@@ -141,6 +153,15 @@
 
 #define MP_STATE_PORT MP_STATE_VM
 
+// Miscellaneous settings
+
+#ifndef MICROPY_HW_USB_VID
+#define MICROPY_HW_USB_VID (0xf055)
+#endif
+#ifndef MICROPY_HW_USB_PID
+#define MICROPY_HW_USB_PID (0x9802)
+#endif
+
 // Additional entries for use with pendsv_schedule_dispatch.
 #ifndef MICROPY_BOARD_PENDSV_ENTRIES
 #define MICROPY_BOARD_PENDSV_ENTRIES
diff --git a/ports/samd/mphalport.c b/ports/samd/mphalport.c
index dc38ea2964eb..3c803403f213 100644
--- a/ports/samd/mphalport.c
+++ b/ports/samd/mphalport.c
@@ -29,6 +29,7 @@
 #include "py/mphal.h"
 #include "py/stream.h"
 #include "shared/runtime/interrupt_char.h"
+#include "shared/tinyusb/mp_usbd.h"
 #include "extmod/misc.h"
 #include "samd_soc.h"
 #include "tusb.h"
@@ -42,6 +43,14 @@ extern volatile uint32_t ticks_us64_upper;
 STATIC uint8_t stdin_ringbuf_array[MICROPY_HW_STDIN_BUFFER_LEN];
 ringbuf_t stdin_ringbuf = { stdin_ringbuf_array, sizeof(stdin_ringbuf_array), 0, 0 };
 
+// Explicitly run the USB stack in case the scheduler is locked (eg we are in an
+// interrupt handler) and there is in/out data pending on the USB CDC interface.
+#define MICROPY_EVENT_POLL_HOOK_WITH_USB \
+    do { \
+        MICROPY_EVENT_POLL_HOOK; \
+        mp_usbd_task(); \
+    } while (0)
+
 uint8_t cdc_itf_pending; // keep track of cdc interfaces which need attention to poll
 
 void poll_cdc_interfaces(void) {
@@ -187,7 +196,7 @@ int mp_hal_stdin_rx_chr(void) {
             return dupterm_c;
         }
         #endif
-        MICROPY_EVENT_POLL_HOOK
+        MICROPY_EVENT_POLL_HOOK_WITH_USB;
     }
 }
 
@@ -201,7 +210,7 @@ void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
             int timeout = 0;
             // Wait with a max of USC_CDC_TIMEOUT ms
             while (n > tud_cdc_write_available() && timeout++ < MICROPY_HW_USB_CDC_TX_TIMEOUT) {
-                MICROPY_EVENT_POLL_HOOK
+                MICROPY_EVENT_POLL_HOOK_WITH_USB;
             }
             if (timeout >= MICROPY_HW_USB_CDC_TX_TIMEOUT) {
                 break;
diff --git a/ports/samd/mphalport.h b/ports/samd/mphalport.h
index 83ccf44222d3..ee33e7446286 100644
--- a/ports/samd/mphalport.h
+++ b/ports/samd/mphalport.h
@@ -35,6 +35,9 @@
 #include "hpl_time_measure.h"
 #include "sam.h"
 
+#define MICROPY_PY_PENDSV_ENTER   uint32_t atomic_state = raise_irq_pri(IRQ_PRI_PENDSV)
+#define MICROPY_PY_PENDSV_EXIT    restore_irq_pri(atomic_state)
+
 #define MICROPY_HW_USB_CDC_TX_TIMEOUT (500)
 
 extern int mp_interrupt_char;
diff --git a/ports/samd/samd_soc.c b/ports/samd/samd_soc.c
index ad5910301cfc..dcfff9dc2274 100644
--- a/ports/samd/samd_soc.c
+++ b/ports/samd/samd_soc.c
@@ -153,3 +153,39 @@ void sercom_deinit_all(void) {
 }
 
 #endif
+
+void samd_get_unique_id(samd_unique_id_t *id) {
+    // Atmel SAM D21E / SAM D21G / SAM D21J
+    // SMART ARM-Based Microcontroller
+    // DATASHEET
+    // 9.6 (SAMD51) or 9.3.3 (or 10.3.3 depending on which manual)(SAMD21) Serial Number
+    //
+    // EXAMPLE (SAMD21)
+    // ----------------
+    // OpenOCD:
+    // Word0:
+    // > at91samd21g18.cpu mdw 0x0080A00C 1
+    // 0x0080a00c: 6e27f15f
+    // Words 1-3:
+    // > at91samd21g18.cpu mdw 0x0080A040 3
+    // 0x0080a040: 50534b54 332e3120 ff091645
+    //
+    // MicroPython (this code and same order as shown in Arduino IDE)
+    // >>> binascii.hexlify(machine.unique_id())
+    // b'6e27f15f50534b54332e3120ff091645'
+
+    #if defined(MCU_SAMD21)
+    uint32_t *id_addresses[4] = {(uint32_t *)0x0080A00C, (uint32_t *)0x0080A040,
+                                 (uint32_t *)0x0080A044, (uint32_t *)0x0080A048};
+    #elif defined(MCU_SAMD51)
+    uint32_t *id_addresses[4] = {(uint32_t *)0x008061FC, (uint32_t *)0x00806010,
+                                 (uint32_t *)0x00806014, (uint32_t *)0x00806018};
+    #endif
+
+    for (int i = 0; i < 4; i++) {
+        for (int k = 0; k < 4; k++) {
+            // 'Reverse' the read bytes into a 32 bit word (Consistent with Arduino)
+            id->bytes[4 * i + k] = (*(id_addresses[i]) >> (24 - k * 8)) & 0xff;
+        }
+    }
+}
diff --git a/ports/samd/samd_soc.h b/ports/samd/samd_soc.h
index 90a5a57ffa14..707d2f8edfa9 100644
--- a/ports/samd/samd_soc.h
+++ b/ports/samd/samd_soc.h
@@ -30,6 +30,10 @@
 #include "sam.h"
 #include "clock_config.h"
 
+typedef struct _samd_unique_id_t {
+    uint8_t bytes[16];
+} samd_unique_id_t;
+
 extern Sercom *sercom_instance[];
 
 void samd_init(void);
@@ -40,6 +44,10 @@ void USB_Handler_wrapper(void);
 void sercom_enable(Sercom *spi, int state);
 void sercom_register_irq(int sercom_id, void (*sercom_irq_handler));
 
+// Each device has a unique 128-bit serial number. The uniqueness of the serial number is
+// guaranteed only when using all 128 bits.
+void samd_get_unique_id(samd_unique_id_t *id);
+
 #define SERCOM_IRQ_TYPE_UART  (0)
 #define SERCOM_IRQ_TYPE_SPI   (1)
 #define SERCOM_IRQ_TYPE_I2C   (2)
diff --git a/ports/samd/tusb_port.c b/ports/samd/tusb_port.c
deleted file mode 100644
index e56ef0fd6af0..000000000000
--- a/ports/samd/tusb_port.c
+++ /dev/null
@@ -1,122 +0,0 @@
-/*
- * This file is part of the MicroPython project, http://micropython.org/
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2019 Damien P. George
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "samd_soc.h"
-#include "tusb.h"
-
-#ifndef MICROPY_HW_USB_VID
-#define MICROPY_HW_USB_VID (0xf055)
-#define MICROPY_HW_USB_PID (0x9802)
-#endif
-
-#define USBD_DESC_LEN (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN)
-#define USBD_MAX_POWER_MA (250)
-
-#define USBD_ITF_CDC (0) // needs 2 interfaces
-#define USBD_ITF_MAX (2)
-
-#define USBD_CDC_EP_CMD (0x81)
-#define USBD_CDC_EP_OUT (0x02)
-#define USBD_CDC_EP_IN (0x82)
-#define USBD_CDC_CMD_MAX_SIZE (8)
-#define USBD_CDC_IN_OUT_MAX_SIZE (64)
-
-#define USBD_STR_0 (0x00)
-#define USBD_STR_MANUF (0x01)
-#define USBD_STR_PRODUCT (0x02)
-#define USBD_STR_SERIAL (0x03)
-#define USBD_STR_CDC (0x04)
-
-// Note: descriptors returned from callbacks must exist long enough for transfer to complete
-
-static const tusb_desc_device_t usbd_desc_device = {
-    .bLength = sizeof(tusb_desc_device_t),
-    .bDescriptorType = TUSB_DESC_DEVICE,
-    .bcdUSB = 0x0200,
-    .bDeviceClass = TUSB_CLASS_MISC,
-    .bDeviceSubClass = MISC_SUBCLASS_COMMON,
-    .bDeviceProtocol = MISC_PROTOCOL_IAD,
-    .bMaxPacketSize0 = CFG_TUD_ENDOINT0_SIZE,
-    .idVendor = MICROPY_HW_USB_VID,
-    .idProduct = MICROPY_HW_USB_PID,
-    .bcdDevice = 0x0100,
-    .iManufacturer = USBD_STR_MANUF,
-    .iProduct = USBD_STR_PRODUCT,
-    .iSerialNumber = USBD_STR_SERIAL,
-    .bNumConfigurations = 1,
-};
-
-static const uint8_t usbd_desc_cfg[USBD_DESC_LEN] = {
-    TUD_CONFIG_DESCRIPTOR(1, USBD_ITF_MAX, USBD_STR_0, USBD_DESC_LEN,
-        TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, USBD_MAX_POWER_MA),
-
-    TUD_CDC_DESCRIPTOR(USBD_ITF_CDC, USBD_STR_CDC, USBD_CDC_EP_CMD,
-        USBD_CDC_CMD_MAX_SIZE, USBD_CDC_EP_OUT, USBD_CDC_EP_IN, USBD_CDC_IN_OUT_MAX_SIZE),
-};
-
-static const char *const usbd_desc_str[] = {
-    [USBD_STR_MANUF] = "MicroPython",
-    [USBD_STR_PRODUCT] = "Board in FS mode",
-    [USBD_STR_SERIAL] = "000000000000", // TODO
-    [USBD_STR_CDC] = "Board CDC",
-};
-
-const uint8_t *tud_descriptor_device_cb(void) {
-    return (const uint8_t *)&usbd_desc_device;
-}
-
-const uint8_t *tud_descriptor_configuration_cb(uint8_t index) {
-    (void)index;
-    return usbd_desc_cfg;
-}
-
-const uint16_t *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
-    #define DESC_STR_MAX (20)
-    static uint16_t desc_str[DESC_STR_MAX];
-
-    uint8_t len;
-    if (index == 0) {
-        desc_str[1] = 0x0409; // supported language is English
-        len = 1;
-    } else {
-        if (index >= sizeof(usbd_desc_str) / sizeof(usbd_desc_str[0])) {
-            return NULL;
-        }
-        const char *str = usbd_desc_str[index];
-        for (len = 0; len < DESC_STR_MAX - 1 && str[len]; ++len) {
-            desc_str[1 + len] = str[len];
-        }
-    }
-
-    // first byte is length (including header), second byte is string type
-    desc_str[0] = (TUSB_DESC_STRING << 8) | (2 * len + 2);
-
-    return desc_str;
-}
-
-void USB_Handler_wrapper(void) {
-    tud_int_handler(0);
-}
diff --git a/ports/samd/tusb_config.h b/ports/samd/usbd.c
similarity index 64%
rename from ports/samd/tusb_config.h
rename to ports/samd/usbd.c
index 07fa680cbbb6..2e3200ad7d2b 100644
--- a/ports/samd/tusb_config.h
+++ b/ports/samd/usbd.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2019 Damien P. George
+ * Copyright (c) 2023 Angus Gratton
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -23,25 +23,25 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-#ifndef MICROPY_INCLUDED_SAMD_TUSB_CONFIG_H
-#define MICROPY_INCLUDED_SAMD_TUSB_CONFIG_H
 
-// Common configuration
+#include "py/mpconfig.h"
 
-#if defined(MCU_SAMD21)
-#define CFG_TUSB_MCU                OPT_MCU_SAMD21
-#elif defined(MCU_SAMD51)
-#define CFG_TUSB_MCU                OPT_MCU_SAMD51
-#endif
-#define CFG_TUSB_RHPORT0_MODE       OPT_MODE_DEVICE
-#define CFG_TUSB_MEM_SECTION
-#define CFG_TUSB_MEM_ALIGN          TU_ATTR_ALIGNED(4)
+#if MICROPY_HW_ENABLE_USBDEV
+
+#include "mp_usbd.h"
+#include "string.h"
+#include "tusb.h"
+#include "samd_soc.h"
 
-// Device configuration
+void mp_usbd_port_get_serial_number(char *serial_buf) {
+    samd_unique_id_t id;
+    samd_get_unique_id(&id);
+    MP_STATIC_ASSERT(sizeof(id.bytes) * 2 <= MICROPY_HW_USB_DESC_STR_MAX);
+    mp_usbd_hex_str(serial_buf, id.bytes, sizeof(id.bytes));
+}
 
-#define CFG_TUD_ENDOINT0_SIZE       (64)
-#define CFG_TUD_CDC                 (1)
-#define CFG_TUD_CDC_RX_BUFSIZE      (64)
-#define CFG_TUD_CDC_TX_BUFSIZE      (64)
+void USB_Handler_wrapper(void) {
+    tud_int_handler(0);
+}
 
-#endif // MICROPY_INCLUDED_SAMD_TUSB_CONFIG_H
+#endif
diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index edebd2db9d8f..56b5a1020c5e 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -408,7 +408,7 @@ HAL_SRC_C += $(addprefix $(STM32LIB_HAL_BASE)/Src/stm32$(MCU_SERIES)xx_,\
 	)
 endif
 
-ifeq ($(MCU_SERIES),$(filter $(MCU_SERIES),f4 f7 h7 l4))
+ifeq ($(MCU_SERIES),$(filter $(MCU_SERIES),f4 f7 h5 h7 l4))
 HAL_SRC_C += $(addprefix $(STM32LIB_HAL_BASE)/Src/stm32$(MCU_SERIES)xx_,\
 	hal_sd.c \
 	ll_sdmmc.c \
diff --git a/ports/stm32/boards/ARDUINO_GIGA/mpconfigboard.h b/ports/stm32/boards/ARDUINO_GIGA/mpconfigboard.h
index ec9bbed5ea6e..b278fa005b75 100644
--- a/ports/stm32/boards/ARDUINO_GIGA/mpconfigboard.h
+++ b/ports/stm32/boards/ARDUINO_GIGA/mpconfigboard.h
@@ -4,10 +4,12 @@
  * Copyright (c) 2023 Arduino SA
  */
 
-#define MICROPY_HW_BOARD_NAME       "GIGA"
+#define MICROPY_HW_BOARD_NAME       "Arduino GIGA R1 WiFi"
 #define MICROPY_HW_MCU_NAME         "STM32H747"
-#define MICROPY_PY_SYS_PLATFORM     "Giga"
-#define MICROPY_HW_FLASH_FS_LABEL   "Giga"
+#define MICROPY_HW_FLASH_FS_LABEL   "GIGA R1 WiFi"
+
+// Network config
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "mpy-giga-r1-wifi"
 
 #define MICROPY_OBJ_REPR            (MICROPY_OBJ_REPR_C)
 #define UINT_FMT                    "%u"
diff --git a/ports/stm32/boards/ARDUINO_NICLA_VISION/mpconfigboard.h b/ports/stm32/boards/ARDUINO_NICLA_VISION/mpconfigboard.h
index 3cae9b25fa34..3a2def4d4044 100644
--- a/ports/stm32/boards/ARDUINO_NICLA_VISION/mpconfigboard.h
+++ b/ports/stm32/boards/ARDUINO_NICLA_VISION/mpconfigboard.h
@@ -4,10 +4,12 @@
  * Copyright (c) 2023 Arduino SA
  */
 
-#define MICROPY_HW_BOARD_NAME       "NICLAVISION"
+#define MICROPY_HW_BOARD_NAME       "Arduino Nicla Vision"
 #define MICROPY_HW_MCU_NAME         "STM32H747"
-#define MICROPY_PY_SYS_PLATFORM     "Nicla Vision"
-#define MICROPY_HW_FLASH_FS_LABEL   "niclavision"
+#define MICROPY_HW_FLASH_FS_LABEL   "Nicla Vision"
+
+// Network config
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "mpy-nicla-vision"
 
 #define MICROPY_OBJ_REPR            (MICROPY_OBJ_REPR_C)
 #define UINT_FMT                    "%u"
diff --git a/ports/stm32/boards/ARDUINO_PORTENTA_H7/mpconfigboard.h b/ports/stm32/boards/ARDUINO_PORTENTA_H7/mpconfigboard.h
index 133158c60add..e2e6956a47d6 100644
--- a/ports/stm32/boards/ARDUINO_PORTENTA_H7/mpconfigboard.h
+++ b/ports/stm32/boards/ARDUINO_PORTENTA_H7/mpconfigboard.h
@@ -4,12 +4,12 @@
  * Copyright (c) 2022 Arduino SA
  */
 
-#define MICROPY_HW_BOARD_NAME       "PORTENTA"
+#define MICROPY_HW_BOARD_NAME       "Arduino Portenta H7"
 #define MICROPY_HW_MCU_NAME         "STM32H747"
-#define MICROPY_PY_SYS_PLATFORM     "Portenta"
-#define MICROPY_HW_FLASH_FS_LABEL   "portenta"
+#define MICROPY_HW_FLASH_FS_LABEL   "Portenta H7"
 
-#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "Portenta"
+// Network config
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "mpy-portenta-h7"
 
 #define MICROPY_OBJ_REPR            (MICROPY_OBJ_REPR_C)
 #define UINT_FMT                    "%u"
diff --git a/ports/stm32/boards/NUCLEO_F446RE/mpconfigboard.h b/ports/stm32/boards/NUCLEO_F446RE/mpconfigboard.h
index 88bfd39b4166..a0a6dbf8c51e 100644
--- a/ports/stm32/boards/NUCLEO_F446RE/mpconfigboard.h
+++ b/ports/stm32/boards/NUCLEO_F446RE/mpconfigboard.h
@@ -16,10 +16,20 @@
 #define MICROPY_HW_CLK_PLLQ (7)
 
 // UART config
-#define MICROPY_HW_UART2_TX     (pin_A2)
-#define MICROPY_HW_UART2_RX     (pin_A3)
-#define MICROPY_HW_UART6_TX     (pin_C6)
-#define MICROPY_HW_UART6_RX     (pin_C7)
+#define MICROPY_HW_UART1_TX     (pin_B6)    // Arduino D10, pin 17 on CN10
+#define MICROPY_HW_UART1_RX     (pin_B7)    //              pin 21 on CN7
+#define MICROPY_HW_UART2_TX     (pin_A2)    // Arduino D1,  pin 35 on CN10
+#define MICROPY_HW_UART2_RX     (pin_A3)    // Arduino D0,  pin 37 on CN10
+#define MICROPY_HW_UART2_RTS    (pin_A1)    // Arduino A1,  pin 30 on CN7
+#define MICROPY_HW_UART2_CTS    (pin_A0)    // Arduino A0,  pin 28 on CN7
+#define MICROPY_HW_UART3_TX     (pin_B10)   // Arduino D6,  pin 25 on CN10
+#define MICROPY_HW_UART3_RX     (pin_C5)    //              pin  6 on CN10
+#define MICROPY_HW_UART3_RTS    (pin_B14)   //              pin 28 on CN10
+#define MICROPY_HW_UART3_CTS    (pin_B13)   //              pin 30 on CN10
+#define MICROPY_HW_UART4_TX     (pin_A0)    // Arduino A0,  pin 28 on CN7
+#define MICROPY_HW_UART4_RX     (pin_A1)    // Arduino A1,  pin 30 on CN7
+#define MICROPY_HW_UART6_TX     (pin_C6)    //              pin  4 on CN10
+#define MICROPY_HW_UART6_RX     (pin_C7)    // Arduino D9,  pin 19 on CN10
 // UART 2 connects to the STM32F103 (STLINK) on the Nucleo board
 // and this is exposed as a USB Serial port.
 #define MICROPY_HW_UART_REPL        PYB_UART_2
diff --git a/ports/stm32/boards/NUCLEO_H563ZI/board.json b/ports/stm32/boards/NUCLEO_H563ZI/board.json
new file mode 100644
index 000000000000..b9c4e41b3eb3
--- /dev/null
+++ b/ports/stm32/boards/NUCLEO_H563ZI/board.json
@@ -0,0 +1,15 @@
+{
+    "deploy": [
+        "../deploy.md"
+    ],
+    "docs": "",
+    "features": [],
+    "images": [
+        "nucleo_h563zi.jpg"
+    ],
+    "mcu": "stm32h5",
+    "product": "Nucleo H563ZI",
+    "thumbnail": "",
+    "url": "",
+    "vendor": "ST Microelectronics"
+}
diff --git a/ports/stm32/boards/NUCLEO_H563ZI/mpconfigboard.h b/ports/stm32/boards/NUCLEO_H563ZI/mpconfigboard.h
new file mode 100644
index 000000000000..1e802eda5b04
--- /dev/null
+++ b/ports/stm32/boards/NUCLEO_H563ZI/mpconfigboard.h
@@ -0,0 +1,91 @@
+#define MICROPY_HW_BOARD_NAME               "NUCLEO_H563ZI"
+#define MICROPY_HW_MCU_NAME                 "STM32H563ZI"
+
+#define MICROPY_PY_PYB_LEGACY               (0)
+#define MICROPY_HW_ENABLE_INTERNAL_FLASH_STORAGE (1)
+#define MICROPY_HW_ENABLE_RTC               (1)
+#define MICROPY_HW_ENABLE_RNG               (1)
+#define MICROPY_HW_ENABLE_ADC               (1)
+#define MICROPY_HW_ENABLE_DAC               (1)
+#define MICROPY_HW_ENABLE_USB               (1)
+#define MICROPY_HW_HAS_SWITCH               (1)
+#define MICROPY_HW_HAS_FLASH                (1)
+
+// The board has a 8MHz oscillator, the following gives 250MHz CPU speed
+#define MICROPY_HW_CLK_USE_BYPASS           (1)
+#define MICROPY_HW_CLK_PLLM                 (2)
+#define MICROPY_HW_CLK_PLLN                 (125)
+#define MICROPY_HW_CLK_PLLP                 (2)
+#define MICROPY_HW_CLK_PLLQ                 (2)
+#define MICROPY_HW_CLK_PLLR                 (2)
+#define MICROPY_HW_CLK_PLLVCI_LL            (LL_RCC_PLLINPUTRANGE_4_8)
+#define MICROPY_HW_CLK_PLLVCO_LL            (LL_RCC_PLLVCORANGE_WIDE)
+#define MICROPY_HW_CLK_PLLFRAC              (0)
+
+// PLL3 with Q output at 48MHz for USB
+// #define MICROPY_HW_CLK_USE_PLL3_FOR_USB
+#define MICROPY_HW_CLK_PLL3M                (8)
+#define MICROPY_HW_CLK_PLL3N                (192)
+#define MICROPY_HW_CLK_PLL3P                (2)
+#define MICROPY_HW_CLK_PLL3Q                (4)
+#define MICROPY_HW_CLK_PLL3R                (2)
+#define MICROPY_HW_CLK_PLL3FRAC             (0)
+#define MICROPY_HW_CLK_PLL3VCI_LL           (LL_RCC_PLLINPUTRANGE_1_2)
+#define MICROPY_HW_CLK_PLL3VCO_LL           (LL_RCC_PLLVCORANGE_MEDIUM)
+
+// 5 wait states, according to Table 37, Reference Manual (RM0481 Rev 1)
+#define MICROPY_HW_FLASH_LATENCY            FLASH_LATENCY_5
+
+// There is an external 32kHz oscillator
+#define MICROPY_HW_RTC_USE_LSE              (1)
+
+// UART config
+#define MICROPY_HW_UART1_TX                 (pin_B6) // SB14: Arduino Connector CN10-Pin14 (D1)
+#define MICROPY_HW_UART1_RX                 (pin_B7) // SB63: Arduino Connector CN10-Pin16 (D0)
+#define MICROPY_HW_UART3_TX                 (pin_D8) // SB23: ST-Link
+#define MICROPY_HW_UART3_RX                 (pin_D9) // SB18: ST-Link
+
+// Connect REPL to UART3 which is provided on ST-Link USB interface
+#define MICROPY_HW_UART_REPL                PYB_UART_3
+#define MICROPY_HW_UART_REPL_BAUD           115200
+
+// I2C buses
+#define MICROPY_HW_I2C1_SCL                 (pin_B8) // Arduino Connector CN7-Pin2 (D15)
+#define MICROPY_HW_I2C1_SDA                 (pin_B9) // Arduino Connector CN7-Pin4 (D14)
+#define MICROPY_HW_I2C2_SCL                 (pin_F1) // Connector CN9-Pin19
+#define MICROPY_HW_I2C2_SDA                 (pin_F0) // Connector CN9-Pin21
+
+// SPI buses
+// PD14 according to datasheet not working as SPI1_NSS, have to use as GPIO, not as AF
+#define MICROPY_HW_SPI1_NSS                 (pin_D14) // Arduino Connector CN7-Pin16 (D10)
+#define MICROPY_HW_SPI1_SCK                 (pin_A5) // Arduino Connector CN7-Pin10 (D13)
+#define MICROPY_HW_SPI1_MISO                (pin_G9) // Arduino Connector CN7-Pin12 (D12)
+#define MICROPY_HW_SPI1_MOSI                (pin_B5) // Arduino Connector CN7-Pin14 (D11)
+
+// USRSW is pulled low. Pressing the button makes the input go high.
+#define MICROPY_HW_USRSW_PIN                (pin_C13)
+#define MICROPY_HW_USRSW_PULL               (GPIO_NOPULL)
+#define MICROPY_HW_USRSW_EXTI_MODE          (GPIO_MODE_IT_RISING)
+#define MICROPY_HW_USRSW_PRESSED            (1)
+
+// LEDs
+#define MICROPY_HW_LED1                     (pin_B0) // Green
+#define MICROPY_HW_LED2                     (pin_F4) // Orange
+#define MICROPY_HW_LED3                     (pin_G4) // Red
+#define MICROPY_HW_LED_ON(pin)              (mp_hal_pin_high(pin))
+#define MICROPY_HW_LED_OFF(pin)             (mp_hal_pin_low(pin))
+
+// USB config
+#define MICROPY_HW_USB_FS                   (1)
+#define MICROPY_HW_USB_MAIN_DEV             (USB_PHY_FS_ID)
+
+// Ethernet via RMII
+#define MICROPY_HW_ETH_MDC          (pin_C1)
+#define MICROPY_HW_ETH_MDIO         (pin_A2)
+#define MICROPY_HW_ETH_RMII_REF_CLK (pin_A1)
+#define MICROPY_HW_ETH_RMII_CRS_DV  (pin_A7)
+#define MICROPY_HW_ETH_RMII_RXD0    (pin_C4)
+#define MICROPY_HW_ETH_RMII_RXD1    (pin_C5)
+#define MICROPY_HW_ETH_RMII_TX_EN   (pin_G11)
+#define MICROPY_HW_ETH_RMII_TXD0    (pin_G13)
+#define MICROPY_HW_ETH_RMII_TXD1    (pin_B15)
diff --git a/ports/stm32/boards/NUCLEO_H563ZI/mpconfigboard.mk b/ports/stm32/boards/NUCLEO_H563ZI/mpconfigboard.mk
new file mode 100644
index 000000000000..a55a54d1c76d
--- /dev/null
+++ b/ports/stm32/boards/NUCLEO_H563ZI/mpconfigboard.mk
@@ -0,0 +1,23 @@
+USE_MBOOT ?= 0
+
+# MCU settings
+MCU_SERIES = h5
+CMSIS_MCU = STM32H573xx
+MICROPY_FLOAT_IMPL = single
+AF_FILE = boards/stm32h573_af.csv
+
+ifeq ($(USE_MBOOT),1)
+# When using Mboot everything goes after the bootloader
+# TODO: not tested
+LD_FILES = boards/stm32h573xi.ld boards/common_bl.ld
+TEXT0_ADDR = 0x08008000
+else
+# When not using Mboot everything goes at the start of flash
+LD_FILES = boards/stm32h573xi.ld boards/common_basic.ld
+TEXT0_ADDR = 0x08000000
+endif
+
+# MicroPython settings
+MICROPY_PY_LWIP = 1
+MICROPY_PY_SSL = 1
+MICROPY_SSL_MBEDTLS = 1
diff --git a/ports/stm32/boards/NUCLEO_H563ZI/pins.csv b/ports/stm32/boards/NUCLEO_H563ZI/pins.csv
new file mode 100644
index 000000000000..1f83e8a505b8
--- /dev/null
+++ b/ports/stm32/boards/NUCLEO_H563ZI/pins.csv
@@ -0,0 +1,130 @@
+,PA0
+,PA1
+,PA2
+,PA3
+,PA4
+,PA5
+,PA7
+,PA8
+,PA9
+,PA10
+,PA11
+,PA12
+,PA13
+,PA14
+,PA15
+,PB0
+,PB2
+,PB3
+,PB4
+,PB5
+,PB6
+,PB7
+,PB8
+,PB9
+,PB10
+,PB11
+,PB12
+,PB13
+,PB14
+,PB15
+,PC1
+,PC4
+,PC5
+,PC6
+,PC7
+,PC8
+,PC9
+,PC10
+,PC11
+,PC12
+,PC13
+,PC14
+,PC15
+,PD0
+,PD1
+,PD2
+,PD3
+,PD4
+,PD5
+,PD6
+,PD7
+,PD8
+,PD9
+,PD10
+,PD11
+,PD12
+,PD13
+,PD14
+,PE0
+,PE1
+,PE2
+,PE3
+,PE4
+,PE5
+,PE6
+,PE7
+,PE8
+,PE10
+,PE12
+,PE15
+,PF0
+,PF1
+,PF2
+,PF4
+,PF5
+,PF6
+,PF7
+,PF8
+,PF9
+,PF10
+,PF12
+,PF13
+,PF14
+,PF15
+,PG0
+,PG1
+,PG2
+,PG3
+,PG4
+,PG5
+,PG6
+,PG7
+,PG8
+,PG9
+,PG10
+,PG11
+,PG13
+,PG15
+A0,PA6
+A1,PC0
+A2,PC3
+A3,PB1
+A4,PC2
+A5,PF11
+D2,PG14
+D3,PE13
+D4,PE14
+D5,PE11
+D6,PE9
+D7,PG12
+D8,PF3
+D9,PD15
+UART1_TX,PB6
+UART1_RX,PB7
+UART3_TX,PD8
+UART3_RX,PD9
+LED_GREEN,PB0
+LED_ORANGE,PF4
+LED_RED,PG4
+SW,PC13
+I2C1_SDA,PB9
+I2C1_SCL,PB8
+I2C2_SDA,PF1
+I2C2_SCL,PF0
+USB_DM,PA11
+USB_DP,PA12
+SPI_A_CS,PD14
+SPI_A_SCK,PA5
+SPI_A_MOSI,PB5
+SPI_A_MISO,PG9
diff --git a/ports/stm32/boards/NUCLEO_H563ZI/stm32h5xx_hal_conf.h b/ports/stm32/boards/NUCLEO_H563ZI/stm32h5xx_hal_conf.h
new file mode 100644
index 000000000000..f86c9300e387
--- /dev/null
+++ b/ports/stm32/boards/NUCLEO_H563ZI/stm32h5xx_hal_conf.h
@@ -0,0 +1,19 @@
+/* This file is part of the MicroPython project, http://micropython.org/
+ * The MIT License (MIT)
+ * Copyright (c) 2023 Damien P. George
+ */
+#ifndef MICROPY_INCLUDED_STM32H5XX_HAL_CONF_H
+#define MICROPY_INCLUDED_STM32H5XX_HAL_CONF_H
+
+// Oscillator values in Hz
+#define HSE_VALUE (8000000)
+#define LSE_VALUE (32768)
+#define EXTERNAL_CLOCK_VALUE (12288000)
+
+// Oscillator timeouts in ms
+#define HSE_STARTUP_TIMEOUT (100)
+#define LSE_STARTUP_TIMEOUT (5000)
+
+#include "boards/stm32h5xx_hal_conf_base.h"
+
+#endif // MICROPY_INCLUDED_STM32H5XX_HAL_CONF_H
diff --git a/ports/stm32/boards/STM32H573I_DK/mpconfigboard.h b/ports/stm32/boards/STM32H573I_DK/mpconfigboard.h
index fba14329a5ce..c8e0340af1ec 100644
--- a/ports/stm32/boards/STM32H573I_DK/mpconfigboard.h
+++ b/ports/stm32/boards/STM32H573I_DK/mpconfigboard.h
@@ -8,6 +8,7 @@
 #define MICROPY_HW_ENABLE_ADC               (1)
 #define MICROPY_HW_ENABLE_DAC               (1)
 #define MICROPY_HW_ENABLE_USB               (1)
+#define MICROPY_HW_ENABLE_SDCARD            (1)
 #define MICROPY_HW_HAS_SWITCH               (1)
 #define MICROPY_HW_HAS_FLASH                (1)
 
@@ -106,6 +107,11 @@
 #define MICROPY_HW_USB_FS                   (1)
 #define MICROPY_HW_USB_MAIN_DEV             (USB_PHY_FS_ID)
 
+// SD card
+#define MICROPY_HW_SDCARD_DETECT_PIN        (pin_H14)
+#define MICROPY_HW_SDCARD_DETECT_PULL       (GPIO_PULLUP)
+#define MICROPY_HW_SDCARD_DETECT_PRESENT    (GPIO_PIN_RESET)
+
 // Ethernet via RMII
 #define MICROPY_HW_ETH_MDC                  (pin_C1)
 #define MICROPY_HW_ETH_MDIO                 (pin_A2)
diff --git a/ports/stm32/dma.c b/ports/stm32/dma.c
index 0a5d25c16cc7..af56d812367c 100644
--- a/ports/stm32/dma.c
+++ b/ports/stm32/dma.c
@@ -156,7 +156,7 @@ static const DMA_InitTypeDef dma_init_struct_i2s = {
 };
 #endif
 
-#if ENABLE_SDIO && !defined(STM32H7)
+#if ENABLE_SDIO && !defined(STM32H5) && !defined(STM32H7)
 // Parameters to dma_init() for SDIO tx and rx.
 static const DMA_InitTypeDef dma_init_struct_sdio = {
     #if defined(STM32F4) || defined(STM32F7)
diff --git a/ports/stm32/i2c.c b/ports/stm32/i2c.c
index 42aba2eccbe5..52f227a950eb 100644
--- a/ports/stm32/i2c.c
+++ b/ports/stm32/i2c.c
@@ -24,6 +24,7 @@
  * THE SOFTWARE.
  */
 
+#include <string.h>
 #include "py/mperrno.h"
 #include "py/mphal.h"
 #include "py/runtime.h"
diff --git a/ports/stm32/lwip_inc/lwipopts.h b/ports/stm32/lwip_inc/lwipopts.h
index 7b2460fa80aa..f641cf515add 100644
--- a/ports/stm32/lwip_inc/lwipopts.h
+++ b/ports/stm32/lwip_inc/lwipopts.h
@@ -24,6 +24,9 @@
 #define LWIP_NETIF_HOSTNAME             1
 #define LWIP_NETIF_EXT_STATUS_CALLBACK  1
 
+#define LWIP_LOOPIF_MULTICAST           1
+#define LWIP_LOOPBACK_MAX_PBUFS         8
+
 #define LWIP_IPV6                       0
 #define LWIP_DHCP                       1
 #define LWIP_DHCP_CHECK_LINK_UP         1
diff --git a/ports/stm32/machine_i2s.c b/ports/stm32/machine_i2s.c
index dbcd9352d5bd..b3e1cee34f32 100644
--- a/ports/stm32/machine_i2s.c
+++ b/ports/stm32/machine_i2s.c
@@ -29,6 +29,7 @@
 // extmod/machine_i2s.c via MICROPY_PY_MACHINE_I2S_INCLUDEFILE.
 
 #include <stdlib.h>
+#include <string.h>
 #include "py/mphal.h"
 #include "pin.h"
 #include "dma.h"
diff --git a/ports/stm32/mpnetworkport.c b/ports/stm32/mpnetworkport.c
index 62f780a35a04..3b9591213a8d 100644
--- a/ports/stm32/mpnetworkport.c
+++ b/ports/stm32/mpnetworkport.c
@@ -72,6 +72,10 @@ STATIC void pyb_lwip_poll(void) {
 
     // Run the lwIP internal updates
     sys_check_timeouts();
+
+    #if LWIP_NETIF_LOOPBACK
+    netif_poll_all();
+    #endif
 }
 
 void mod_network_lwip_poll_wrapper(uint32_t ticks_ms) {
diff --git a/ports/stm32/mpu.h b/ports/stm32/mpu.h
index e95a07da91a8..b3e2aec2d807 100644
--- a/ports/stm32/mpu.h
+++ b/ports/stm32/mpu.h
@@ -26,7 +26,7 @@
 #ifndef MICROPY_INCLUDED_STM32_MPU_H
 #define MICROPY_INCLUDED_STM32_MPU_H
 
-#if (defined(STM32F4) && defined(MICROPY_HW_ETH_MDC)) || defined(STM32F7) || defined(STM32H7)
+#if (defined(STM32F4) && defined(MICROPY_HW_ETH_MDC)) || defined(STM32F7) || defined(STM32H7) || defined(STM32WB)
 
 #define MPU_REGION_ETH      (MPU_REGION_NUMBER0)
 #define MPU_REGION_QSPI1    (MPU_REGION_NUMBER1)
diff --git a/ports/stm32/pin_static_af.h b/ports/stm32/pin_static_af.h
index 49580a278746..86ae90ba4c6c 100644
--- a/ports/stm32/pin_static_af.h
+++ b/ports/stm32/pin_static_af.h
@@ -26,6 +26,9 @@
 #ifndef MICROPY_INCLUDED_STM32_PIN_STATIC_AF_H
 #define MICROPY_INCLUDED_STM32_PIN_STATIC_AF_H
 
+// For debug builds some of the macros expand to use strcmp.
+#include <string.h>
+
 #include "py/mphal.h"
 #include "genhdr/pins.h"
 #include "genhdr/pins_af_defs.h"
diff --git a/ports/stm32/sdcard.c b/ports/stm32/sdcard.c
index d09ee21d09bf..a903f79ed216 100644
--- a/ports/stm32/sdcard.c
+++ b/ports/stm32/sdcard.c
@@ -40,7 +40,7 @@
 
 #if MICROPY_HW_ENABLE_SDCARD || MICROPY_HW_ENABLE_MMCARD
 
-#if defined(STM32F7) || defined(STM32H7) || defined(STM32L4)
+#if defined(STM32F7) || defined(STM32H5) || defined(STM32H7) || defined(STM32L4)
 
 // The H7/F7/L4 have 2 SDMMC peripherals, but at the moment this driver only supports
 // using one of them in a given build, selected by MICROPY_HW_SDCARD_SDMMC.
@@ -104,7 +104,7 @@
 #define SDIO_HARDWARE_FLOW_CONTROL_DISABLE  SDMMC_HARDWARE_FLOW_CONTROL_DISABLE
 #define SDIO_HARDWARE_FLOW_CONTROL_ENABLE   SDMMC_HARDWARE_FLOW_CONTROL_ENABLE
 
-#if defined(STM32H7)
+#if defined(STM32H5) || defined(STM32H7)
 #define SDIO_TRANSFER_CLK_DIV               SDMMC_NSpeed_CLK_DIV
 #define SDIO_USE_GPDMA                      0
 #else
@@ -268,7 +268,7 @@ STATIC HAL_StatusTypeDef sdmmc_init_sd(void) {
     // SD device interface configuration
     sdmmc_handle.sd.Instance = SDIO;
     sdmmc_handle.sd.Init.ClockEdge = SDIO_CLOCK_EDGE_RISING;
-    #ifndef STM32H7
+    #if !defined(STM32H5) && !defined(STM32H7)
     sdmmc_handle.sd.Init.ClockBypass = SDIO_CLOCK_BYPASS_DISABLE;
     #endif
     sdmmc_handle.sd.Init.ClockPowerSave = SDIO_CLOCK_POWER_SAVE_ENABLE;
diff --git a/ports/stm32/spi.c b/ports/stm32/spi.c
index 47714a28725b..ee2301c803b8 100644
--- a/ports/stm32/spi.c
+++ b/ports/stm32/spi.c
@@ -24,6 +24,7 @@
  * THE SOFTWARE.
  */
 
+#include <string.h>
 #include "py/runtime.h"
 #include "py/mperrno.h"
 #include "py/mphal.h"
diff --git a/py/misc.h b/py/misc.h
index 352a9f34c451..e19a535720fb 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -52,10 +52,15 @@ typedef unsigned int uint;
 
 // Static assertion macro
 #define MP_STATIC_ASSERT(cond) ((void)sizeof(char[1 - 2 * !(cond)]))
-#if defined(_MSC_VER)
-#define MP_STATIC_ASSERT_NOT_MSC(cond) (1)
+// In C++ things like comparing extern const pointers are not constant-expressions so cannot be used
+// in MP_STATIC_ASSERT. Note that not all possible compiler versions will reject this. Some gcc versions
+// do, others only with -Werror=vla, msvc always does.
+// The (void) is needed to avoid "left operand of comma operator has no effect [-Werror=unused-value]"
+// when using this macro on the left-hand side of a comma.
+#if defined(_MSC_VER) || defined(__cplusplus)
+#define MP_STATIC_ASSERT_NONCONSTEXPR(cond) ((void)1)
 #else
-#define MP_STATIC_ASSERT_NOT_MSC(cond) MP_STATIC_ASSERT(cond)
+#define MP_STATIC_ASSERT_NONCONSTEXPR(cond) MP_STATIC_ASSERT(cond)
 #endif
 
 // Round-up integer division
diff --git a/py/mkrules.cmake b/py/mkrules.cmake
index 7622cd903a88..743302aea98e 100644
--- a/py/mkrules.cmake
+++ b/py/mkrules.cmake
@@ -218,10 +218,27 @@ if(MICROPY_FROZEN_MANIFEST)
         set(MICROPY_CROSS_FLAGS "-f${MICROPY_CROSS_FLAGS}")
     endif()
 
+    # Set default path variables to be passed to makemanifest.py. These will
+    # be available in path substitutions. Additional variables can be set
+    # per-board in mpconfigboard.cmake.
+    set(MICROPY_MANIFEST_PORT_DIR ${MICROPY_PORT_DIR})
+    set(MICROPY_MANIFEST_BOARD_DIR ${MICROPY_BOARD_DIR})
+    set(MICROPY_MANIFEST_MPY_DIR ${MICROPY_DIR})
+    set(MICROPY_MANIFEST_MPY_LIB_DIR ${MICROPY_LIB_DIR})
+
+    # Find all MICROPY_MANIFEST_* variables and turn them into command line arguments.
+    get_cmake_property(_manifest_vars VARIABLES)
+    list(FILTER _manifest_vars INCLUDE REGEX "MICROPY_MANIFEST_.*")
+    foreach(_manifest_var IN LISTS _manifest_vars)
+        list(APPEND _manifest_var_args "-v")
+        string(REGEX REPLACE "MICROPY_MANIFEST_(.*)" "\\1" _manifest_var_name ${_manifest_var})
+        list(APPEND _manifest_var_args "${_manifest_var_name}=${${_manifest_var}}")
+    endforeach()
+
     add_custom_target(
         BUILD_FROZEN_CONTENT ALL
         BYPRODUCTS ${MICROPY_FROZEN_CONTENT}
-        COMMAND ${Python3_EXECUTABLE} ${MICROPY_DIR}/tools/makemanifest.py -o ${MICROPY_FROZEN_CONTENT} -v "MPY_DIR=${MICROPY_DIR}" -v "MPY_LIB_DIR=${MICROPY_LIB_DIR}" -v "PORT_DIR=${MICROPY_PORT_DIR}" -v "BOARD_DIR=${MICROPY_BOARD_DIR}" -b "${CMAKE_BINARY_DIR}" ${MICROPY_CROSS_FLAGS} --mpy-tool-flags=${MICROPY_MPY_TOOL_FLAGS} ${MICROPY_FROZEN_MANIFEST}
+        COMMAND ${Python3_EXECUTABLE} ${MICROPY_DIR}/tools/makemanifest.py -o ${MICROPY_FROZEN_CONTENT} ${_manifest_var_args} -b "${CMAKE_BINARY_DIR}" ${MICROPY_CROSS_FLAGS} --mpy-tool-flags=${MICROPY_MPY_TOOL_FLAGS} ${MICROPY_FROZEN_MANIFEST}
         DEPENDS
             ${MICROPY_QSTRDEFS_GENERATED}
             ${MICROPY_ROOT_POINTERS}
diff --git a/py/mkrules.mk b/py/mkrules.mk
index 507655932834..7ecb2a5f66b3 100644
--- a/py/mkrules.mk
+++ b/py/mkrules.mk
@@ -199,10 +199,21 @@ CFLAGS += -DMICROPY_QSTR_EXTRA_POOL=mp_qstr_frozen_const_pool
 CFLAGS += -DMICROPY_MODULE_FROZEN_MPY
 CFLAGS += -DMICROPY_MODULE_FROZEN_STR
 
+# Set default path variables to be passed to makemanifest.py. These will be
+# available in path substitutions. Additional variables can be set per-board
+# in mpconfigboard.mk or on the make command line.
+MICROPY_MANIFEST_MPY_LIB_DIR = $(MPY_LIB_DIR)
+MICROPY_MANIFEST_PORT_DIR = $(shell pwd)
+MICROPY_MANIFEST_BOARD_DIR = $(BOARD_DIR)
+MICROPY_MANIFEST_MPY_DIR = $(TOP)
+
+# Find all MICROPY_MANIFEST_* variables and turn them into command line arguments.
+MANIFEST_VARIABLES = $(foreach var,$(filter MICROPY_MANIFEST_%, $(.VARIABLES)),-v "$(subst MICROPY_MANIFEST_,,$(var))=$($(var))")
+
 # to build frozen_content.c from a manifest
 $(BUILD)/frozen_content.c: FORCE $(BUILD)/genhdr/qstrdefs.generated.h $(BUILD)/genhdr/root_pointers.h | $(MICROPY_MPYCROSS_DEPENDENCY)
 	$(Q)test -e "$(MPY_LIB_DIR)/README.md" || (echo -e $(HELP_MPY_LIB_SUBMODULE); false)
-	$(Q)$(MAKE_MANIFEST) -o $@ -v "MPY_DIR=$(TOP)" -v "MPY_LIB_DIR=$(MPY_LIB_DIR)" -v "PORT_DIR=$(shell pwd)" -v "BOARD_DIR=$(BOARD_DIR)" -b "$(BUILD)" $(if $(MPY_CROSS_FLAGS),-f"$(MPY_CROSS_FLAGS)",) --mpy-tool-flags="$(MPY_TOOL_FLAGS)" $(FROZEN_MANIFEST)
+	$(Q)$(MAKE_MANIFEST) -o $@ $(MANIFEST_VARIABLES) -b "$(BUILD)" $(if $(MPY_CROSS_FLAGS),-f"$(MPY_CROSS_FLAGS)",) --mpy-tool-flags="$(MPY_TOOL_FLAGS)" $(FROZEN_MANIFEST)
 endif
 
 ifneq ($(PROG),)
diff --git a/py/modbuiltins.c b/py/modbuiltins.c
index da29e5b67da8..4ff7d445097d 100644
--- a/py/modbuiltins.c
+++ b/py/modbuiltins.c
@@ -137,30 +137,12 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_callable_obj, mp_builtin_callable);
 STATIC mp_obj_t mp_builtin_chr(mp_obj_t o_in) {
     #if MICROPY_PY_BUILTINS_STR_UNICODE
     mp_uint_t c = mp_obj_get_int(o_in);
-    uint8_t str[4];
-    int len = 0;
-    if (c < 0x80) {
-        *str = c;
-        len = 1;
-    } else if (c < 0x800) {
-        str[0] = (c >> 6) | 0xC0;
-        str[1] = (c & 0x3F) | 0x80;
-        len = 2;
-    } else if (c < 0x10000) {
-        str[0] = (c >> 12) | 0xE0;
-        str[1] = ((c >> 6) & 0x3F) | 0x80;
-        str[2] = (c & 0x3F) | 0x80;
-        len = 3;
-    } else if (c < 0x110000) {
-        str[0] = (c >> 18) | 0xF0;
-        str[1] = ((c >> 12) & 0x3F) | 0x80;
-        str[2] = ((c >> 6) & 0x3F) | 0x80;
-        str[3] = (c & 0x3F) | 0x80;
-        len = 4;
-    } else {
+    if (c >= 0x110000) {
         mp_raise_ValueError(MP_ERROR_TEXT("chr() arg not in range(0x110000)"));
     }
-    return mp_obj_new_str_via_qstr((char *)str, len);
+    VSTR_FIXED(buf, 4);
+    vstr_add_char(&buf, c);
+    return mp_obj_new_str_via_qstr(buf.buf, buf.len);
     #else
     mp_int_t ord = mp_obj_get_int(o_in);
     if (0 <= ord && ord <= 0xff) {
diff --git a/py/obj.h b/py/obj.h
index 56ae62172fce..c7b7db0c3834 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -928,10 +928,10 @@ void *mp_obj_malloc_helper(size_t num_bytes, const mp_obj_type_t *type);
 // optimizations (other tricks like using ({ expr; exper; }) or (exp, expr, expr) in mp_obj_is_type() result
 // in missed optimizations)
 #define mp_type_assert_not_bool_int_str_nonetype(t) (                                     \
-    MP_STATIC_ASSERT_NOT_MSC((t) != &mp_type_bool), assert((t) != &mp_type_bool),         \
-    MP_STATIC_ASSERT_NOT_MSC((t) != &mp_type_int), assert((t) != &mp_type_int),           \
-    MP_STATIC_ASSERT_NOT_MSC((t) != &mp_type_str), assert((t) != &mp_type_str),           \
-    MP_STATIC_ASSERT_NOT_MSC((t) != &mp_type_NoneType), assert((t) != &mp_type_NoneType), \
+    MP_STATIC_ASSERT_NONCONSTEXPR((t) != &mp_type_bool), assert((t) != &mp_type_bool),         \
+    MP_STATIC_ASSERT_NONCONSTEXPR((t) != &mp_type_int), assert((t) != &mp_type_int),           \
+    MP_STATIC_ASSERT_NONCONSTEXPR((t) != &mp_type_str), assert((t) != &mp_type_str),           \
+    MP_STATIC_ASSERT_NONCONSTEXPR((t) != &mp_type_NoneType), assert((t) != &mp_type_NoneType), \
     1)
 
 #define mp_obj_is_type(o, t) (mp_type_assert_not_bool_int_str_nonetype(t) && mp_obj_is_exact_type(o, t))
diff --git a/py/objslice.c b/py/objslice.c
index 75fa3bc3f55e..dcd6af8b2856 100644
--- a/py/objslice.c
+++ b/py/objslice.c
@@ -54,7 +54,7 @@ STATIC mp_obj_t slice_unary_op(mp_unary_op_t op, mp_obj_t o_in) {
 
 #if MICROPY_PY_BUILTINS_SLICE_INDICES
 STATIC mp_obj_t slice_indices(mp_obj_t self_in, mp_obj_t length_obj) {
-    mp_int_t length = mp_obj_int_get_checked(length_obj);
+    mp_int_t length = mp_obj_get_int(length_obj);
     mp_bound_slice_t bound_indices;
     mp_obj_slice_indices(self_in, length, &bound_indices);
 
diff --git a/shared/runtime/softtimer.c b/shared/runtime/softtimer.c
index 267610b2694d..468fa95b7208 100644
--- a/shared/runtime/softtimer.c
+++ b/shared/runtime/softtimer.c
@@ -30,42 +30,43 @@
 #include "py/runtime.h"
 #include "softtimer.h"
 
+#ifdef MICROPY_SOFT_TIMER_TICKS_MS
+
 extern __IO uint32_t MICROPY_SOFT_TIMER_TICKS_MS;
 
 volatile uint32_t soft_timer_next;
 
+static inline uint32_t soft_timer_get_ms(void) {
+    return MICROPY_SOFT_TIMER_TICKS_MS;
+}
+
+static void soft_timer_schedule_at_ms(uint32_t ticks_ms) {
+    uint32_t atomic_state = MICROPY_BEGIN_ATOMIC_SECTION();
+    uint32_t uw_tick = MICROPY_SOFT_TIMER_TICKS_MS;
+    if (soft_timer_ticks_diff(ticks_ms, uw_tick) <= 0) {
+        soft_timer_next = uw_tick + 1;
+    } else {
+        soft_timer_next = ticks_ms;
+    }
+    MICROPY_END_ATOMIC_SECTION(atomic_state);
+}
+
+#endif
+
 // Pointer to the pairheap of soft timer objects.
 // This may contain bss/data pointers as well as GC-heap pointers,
 // and is explicitly GC traced by soft_timer_gc_mark_all().
 STATIC soft_timer_entry_t *soft_timer_heap;
 
-static inline int32_t ticks_diff(uint32_t t1, uint32_t t0) {
-    // t1 is after t0 (i.e. positive result) if there exists a uint32_t X <= INT_MAX
-    // such that t0 + X = t1. Otherwise t1 is interpreted to be earlier than
-    // t0 (negative result).
-    return t1 - t0;
-}
-
 STATIC int soft_timer_lt(mp_pairheap_t *n1, mp_pairheap_t *n2) {
     soft_timer_entry_t *e1 = (soft_timer_entry_t *)n1;
     soft_timer_entry_t *e2 = (soft_timer_entry_t *)n2;
-    return ticks_diff(e1->expiry_ms, e2->expiry_ms) < 0;
-}
-
-STATIC void soft_timer_schedule_systick(uint32_t ticks_ms) {
-    uint32_t irq_state = disable_irq();
-    uint32_t uw_tick = MICROPY_SOFT_TIMER_TICKS_MS;
-    if (ticks_diff(ticks_ms, uw_tick) <= 0) {
-        soft_timer_next = uw_tick + 1;
-    } else {
-        soft_timer_next = ticks_ms;
-    }
-    enable_irq(irq_state);
+    return soft_timer_ticks_diff(e1->expiry_ms, e2->expiry_ms) < 0;
 }
 
 void soft_timer_deinit(void) {
     // Pop off all the nodes which are allocated on the GC-heap.
-    uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
+    MICROPY_PY_PENDSV_ENTER;
     soft_timer_entry_t *heap_from = soft_timer_heap;
     soft_timer_entry_t *heap_to = (soft_timer_entry_t *)mp_pairheap_new(soft_timer_lt);
     while (heap_from != NULL) {
@@ -76,14 +77,14 @@ void soft_timer_deinit(void) {
         }
     }
     soft_timer_heap = heap_to;
-    restore_irq_pri(irq_state);
+    MICROPY_PY_PENDSV_EXIT;
 }
 
 // Must be executed at IRQ_PRI_PENDSV
 void soft_timer_handler(void) {
-    uint32_t ticks_ms = MICROPY_SOFT_TIMER_TICKS_MS;
+    uint32_t ticks_ms = soft_timer_get_ms();
     soft_timer_entry_t *heap = soft_timer_heap;
-    while (heap != NULL && ticks_diff(heap->expiry_ms, ticks_ms) <= 0) {
+    while (heap != NULL && soft_timer_ticks_diff(heap->expiry_ms, ticks_ms) <= 0) {
         soft_timer_entry_t *entry = heap;
         heap = (soft_timer_entry_t *)mp_pairheap_pop(soft_timer_lt, &heap->pairheap);
         if (entry->flags & SOFT_TIMER_FLAG_PY_CALLBACK) {
@@ -97,19 +98,17 @@ void soft_timer_handler(void) {
         }
     }
     soft_timer_heap = heap;
-    if (heap == NULL) {
-        // No more timers left, set largest delay possible
-        soft_timer_next = MICROPY_SOFT_TIMER_TICKS_MS;
-    } else {
-        // Set soft_timer_next so SysTick calls us back at the correct time
-        soft_timer_schedule_systick(heap->expiry_ms);
+
+    // Schedule the port's timer to call us back at the correct time.
+    if (heap != NULL) {
+        soft_timer_schedule_at_ms(heap->expiry_ms);
     }
 }
 
 void soft_timer_gc_mark_all(void) {
     // Mark all soft timer nodes that are allocated on the GC-heap.
     // To avoid deep C recursion, pop and recreate the pairheap as nodes are marked.
-    uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
+    MICROPY_PY_PENDSV_ENTER;
     soft_timer_entry_t *heap_from = soft_timer_heap;
     soft_timer_entry_t *heap_to = (soft_timer_entry_t *)mp_pairheap_new(soft_timer_lt);
     while (heap_from != NULL) {
@@ -121,7 +120,7 @@ void soft_timer_gc_mark_all(void) {
         heap_to = (soft_timer_entry_t *)mp_pairheap_push(soft_timer_lt, &heap_to->pairheap, &entry->pairheap);
     }
     soft_timer_heap = heap_to;
-    restore_irq_pri(irq_state);
+    MICROPY_PY_PENDSV_EXIT;
 }
 
 void soft_timer_static_init(soft_timer_entry_t *entry, uint16_t mode, uint32_t delta_ms, void (*cb)(soft_timer_entry_t *)) {
@@ -134,18 +133,18 @@ void soft_timer_static_init(soft_timer_entry_t *entry, uint16_t mode, uint32_t d
 
 void soft_timer_insert(soft_timer_entry_t *entry, uint32_t initial_delta_ms) {
     mp_pairheap_init_node(soft_timer_lt, &entry->pairheap);
-    entry->expiry_ms = MICROPY_SOFT_TIMER_TICKS_MS + initial_delta_ms;
-    uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
+    entry->expiry_ms = soft_timer_get_ms() + initial_delta_ms;
+    MICROPY_PY_PENDSV_ENTER;
     soft_timer_heap = (soft_timer_entry_t *)mp_pairheap_push(soft_timer_lt, &soft_timer_heap->pairheap, &entry->pairheap);
     if (entry == soft_timer_heap) {
-        // This new timer became the earliest one so set soft_timer_next
-        soft_timer_schedule_systick(entry->expiry_ms);
+        // This new timer became the earliest one so schedule a callback.
+        soft_timer_schedule_at_ms(entry->expiry_ms);
     }
-    restore_irq_pri(irq_state);
+    MICROPY_PY_PENDSV_EXIT;
 }
 
 void soft_timer_remove(soft_timer_entry_t *entry) {
-    uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
+    MICROPY_PY_PENDSV_ENTER;
     soft_timer_heap = (soft_timer_entry_t *)mp_pairheap_delete(soft_timer_lt, &soft_timer_heap->pairheap, &entry->pairheap);
-    restore_irq_pri(irq_state);
+    MICROPY_PY_PENDSV_EXIT;
 }
diff --git a/shared/runtime/softtimer.h b/shared/runtime/softtimer.h
index 8603ea13f070..fe5d02b90787 100644
--- a/shared/runtime/softtimer.h
+++ b/shared/runtime/softtimer.h
@@ -48,6 +48,13 @@ typedef struct _soft_timer_entry_t {
 
 extern volatile uint32_t soft_timer_next;
 
+static inline int32_t soft_timer_ticks_diff(uint32_t t1, uint32_t t0) {
+    // t1 is after t0 (i.e. positive result) if there exists a uint32_t X <= INT_MAX
+    // such that t0 + X = t1. Otherwise t1 is interpreted to be earlier than
+    // t0 (negative result).
+    return t1 - t0;
+}
+
 void soft_timer_deinit(void);
 void soft_timer_handler(void);
 void soft_timer_gc_mark_all(void);
@@ -63,4 +70,17 @@ static inline void soft_timer_reinsert(soft_timer_entry_t *entry, uint32_t initi
     soft_timer_insert(entry, initial_delta_ms);
 }
 
+#if !defined(MICROPY_SOFT_TIMER_TICKS_MS)
+// IF MICROPY_SOFT_TIMER_TICKS_MS is not defined then the port must provide the
+// following timer functions:
+// - soft_timer_get_ms() must return a 32-bit millisecond counter that wraps around.
+// - soft_timer_schedule_at_ms(ticks_ms) must schedule a callback of soft_timer_handler()
+//   when the above millisecond counter reaches the given ticks_ms value.  If ticks_ms
+//   is behind the current counter (using int32_t arithmetic) then the callback should
+//   be scheduled immediately.  The callback of soft_timer_handler() should be made at
+//   pend-SV IRQ level, or equivalent.
+uint32_t soft_timer_get_ms(void);
+void soft_timer_schedule_at_ms(uint32_t ticks_ms);
+#endif
+
 #endif // MICROPY_INCLUDED_SHARED_RUNTIME_SOFTTIMER_H
diff --git a/shared/tinyusb/mp_usbd.c b/shared/tinyusb/mp_usbd.c
index 55af3d4fb479..74b3f074927b 100644
--- a/shared/tinyusb/mp_usbd.c
+++ b/shared/tinyusb/mp_usbd.c
@@ -62,4 +62,14 @@ static void mp_usbd_task_callback(mp_sched_node_t *node) {
     mp_usbd_task();
 }
 
+void mp_usbd_hex_str(char *out_str, const uint8_t *bytes, size_t bytes_len) {
+    size_t hex_len = bytes_len * 2;
+    for (int i = 0; i < hex_len; i += 2) {
+        static const char *hexdig = "0123456789abcdef";
+        out_str[i] = hexdig[bytes[i / 2] >> 4];
+        out_str[i + 1] = hexdig[bytes[i / 2] & 0x0f];
+    }
+    out_str[hex_len] = 0;
+}
+
 #endif
diff --git a/shared/tinyusb/mp_usbd.h b/shared/tinyusb/mp_usbd.h
index 340637c95f9c..83a8f8617c08 100644
--- a/shared/tinyusb/mp_usbd.h
+++ b/shared/tinyusb/mp_usbd.h
@@ -36,4 +36,9 @@ void mp_usbd_task(void);
 // Can write a string up to MICROPY_HW_USB_DESC_STR_MAX characters long, plus terminating byte.
 extern void mp_usbd_port_get_serial_number(char *buf);
 
+// Most ports need to write a hexadecimal serial number from a byte array, this
+// is a helper function for this. out_str must be long enough to hold a string of total
+// length (2 * bytes_len + 1) (including NUL terminator).
+void mp_usbd_hex_str(char *out_str, const uint8_t *bytes, size_t bytes_len);
+
 #endif // MICROPY_INCLUDED_SHARED_TINYUSB_USBD_H
diff --git a/tests/basics/slice_indices.py b/tests/basics/slice_indices.py
index b7f439ccca26..ccd7667e9b36 100644
--- a/tests/basics/slice_indices.py
+++ b/tests/basics/slice_indices.py
@@ -25,3 +25,8 @@ def __getitem__(self, idx):
 print(A()[2:7:-2].indices(5))
 print(A()[7:2:2].indices(5))
 print(A()[7:2:-2].indices(5))
+
+try:
+    print(A()[::].indices(None))
+except TypeError:
+    print("TypeError")
diff --git a/tests/net_hosted/asyncio_loopback.py b/tests/net_hosted/asyncio_loopback.py
new file mode 100644
index 000000000000..fd4674544ce7
--- /dev/null
+++ b/tests/net_hosted/asyncio_loopback.py
@@ -0,0 +1,64 @@
+# Test network loopback behaviour
+
+try:
+    import asyncio
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+
+async def client(host, port):
+    print(f"client open_connection to {host}:{port}")
+    reader, writer = await asyncio.open_connection(host, port)
+
+    data_in = b"A" * 100
+
+    print("client writing")
+    writer.write(data_in)
+    await writer.drain()
+
+    await asyncio.sleep(0.1)
+
+    print("client reading")
+    data = await reader.readexactly(100)
+    print(f"client got {len(data)} bytes")
+
+    assert data_in == data
+
+    print("client closing")
+
+    writer.close()
+    await writer.wait_closed()
+
+    print("client closed")
+
+
+async def echo_handler(reader, writer):
+    print("handler reading")
+    await asyncio.sleep(0.1)
+    data = await reader.readexactly(100)
+    print(f"handler got {len(data)} bytes")
+
+    print("handler writing")
+    writer.write(data)
+    await writer.drain()
+
+    print("handler closing")
+
+    writer.close()
+    await writer.wait_closed()
+
+    print("handler closed")
+
+
+async def test(host, port):
+    print(f"create server on {host}:{port}")
+    server = await asyncio.start_server(echo_handler, host, port)
+
+    async with server:
+        print("server started")
+        await client("127.0.0.1", 8080)
+    print("server closed")
+
+
+asyncio.run(test("0.0.0.0", 8080))
diff --git a/tests/net_hosted/asyncio_loopback.py.exp b/tests/net_hosted/asyncio_loopback.py.exp
new file mode 100644
index 000000000000..7110b35e12ca
--- /dev/null
+++ b/tests/net_hosted/asyncio_loopback.py.exp
@@ -0,0 +1,14 @@
+create server on 0.0.0.0:8080
+server started
+client open_connection to 127.0.0.1:8080
+client writing
+handler reading
+client reading
+handler got 100 bytes
+handler writing
+handler closing
+handler closed
+client got 100 bytes
+client closing
+client closed
+server closed