machine: Add time_hardware_pulse_us function.

The difference from `time_pulse_us` is that if the pin is initially equal to *pulse_level* then `time_pulse_us` counts the pulse duration immediately, but `time_hardware_pulse_us` first waits for the different *pulse_level*, then waits the equal to *pulse_level* and then counts pulse duration. Signed-off-by: IhorNehrutsa <[email protected]>
IhorNehrutsa · Nov 5, 2024 · 7a9b45d · 7a9b45d
1 parent 594670e
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diff --git a/docs/library/machine.rst b/docs/library/machine.rst
@@ -198,6 +198,29 @@ Miscellaneous functions
    above. The timeout is the same for both cases and given by *timeout_us* (which
    is in microseconds).
 
+.. function:: time_hardware_pulse_us(pin, pulse_level, timeout_us=1000000, /)
+
+   Time a pulse on the given *pin*, and return the duration of the pulse in
+   microseconds.  The *pulse_level* argument should be 0 to time a low pulse
+   or 1 to time a high pulse.
+
+   If the pin is initially equal to *pulse_level* then first waits until
+   the pin input becomes different from *pulse_level* (***).
+   Then the function waits until the pin input becomes equal to *pulse_level* (**),
+   then the function counts the duration that the pin is equal to *pulse_level* (*).
+
+   The function returns -3 if there was timeout waiting for condition marked (***) above.
+   The function will return -2 if there was timeout waiting for condition marked
+   (**) above, and -1 if there was timeout during the main measurement, marked (*)
+   above. The timeout is the same for all cases and given by *timeout_us* (which
+   is in microseconds).
+
+   The difference from `time_pulse_us` is that if the pin is initially equal to *pulse_level*
+   then `time_pulse_us` counts the pulse duration immediately,
+   but `time_hardware_pulse_us` first waits for the different *pulse_level*,
+   then waits the equal to *pulse_level* and then counts pulse duration.
+   A little bit longer, but higher accuracy.
+
 .. function:: bitstream(pin, encoding, timing, data, /)
 
    Transmits *data* by bit-banging the specified *pin*. The *encoding* argument

diff --git a/extmod/machine_pulse.c b/extmod/machine_pulse.c
@@ -62,4 +62,42 @@ static mp_obj_t machine_time_pulse_us_(size_t n_args, const mp_obj_t *args) {
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_pulse_us_obj, 2, 3, machine_time_pulse_us_);
 
+MP_WEAK mp_uint_t machine_time_hardware_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us) {
+    mp_uint_t start = mp_hal_ticks_us();
+    while (mp_hal_pin_read(pin) == pulse_level) {
+        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout_us) {
+            return (mp_uint_t)-3;
+        }
+    }
+    start = mp_hal_ticks_us();
+    while (mp_hal_pin_read(pin) != pulse_level) {
+        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout_us) {
+            return (mp_uint_t)-2;
+        }
+    }
+    start = mp_hal_ticks_us();
+    while (mp_hal_pin_read(pin) == pulse_level) {
+        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout_us) {
+            return (mp_uint_t)-1;
+        }
+    }
+    return mp_hal_ticks_us() - start;
+}
+
+static mp_obj_t machine_time_hardware_pulse_us_(size_t n_args, const mp_obj_t *args) {
+    mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(args[0]);
+    int level = 0;
+    if (mp_obj_is_true(args[1])) {
+        level = 1;
+    }
+    mp_uint_t timeout_us = 1000000;
+    if (n_args > 2) {
+        timeout_us = mp_obj_get_int(args[2]);
+    }
+    mp_uint_t us = machine_time_hardware_pulse_us(pin, level, timeout_us);
+    // May return -1 or -2 or -3 in case of timeout
+    return mp_obj_new_int(us);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_hardware_pulse_us_obj, 2, 3, machine_time_hardware_pulse_us_);
+
 #endif
diff --git a/extmod/modmachine.c b/extmod/modmachine.c
@@ -188,6 +188,7 @@ static const mp_rom_map_elem_t machine_module_globals_table[] = {
     #endif
     #if MICROPY_PY_MACHINE_PULSE
     { MP_ROM_QSTR(MP_QSTR_time_pulse_us), MP_ROM_PTR(&machine_time_pulse_us_obj) },
+    { MP_ROM_QSTR(MP_QSTR_time_hardware_pulse_us), MP_ROM_PTR(&machine_time_hardware_pulse_us_obj) },
     #endif
 
     // Classes for PinBase and Signal.

diff --git a/extmod/modmachine.h b/extmod/modmachine.h
@@ -255,6 +255,7 @@ MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(machine_deepsleep_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(machine_bootloader_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(machine_bitstream_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_pulse_us_obj);
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_hardware_pulse_us_obj);
 
 #if MICROPY_PY_MACHINE_I2C
 int mp_machine_i2c_transfer_adaptor(mp_obj_base_t *self, uint16_t addr, size_t n, mp_machine_i2c_buf_t *bufs, unsigned int flags);