machine: Add wait_opposite to time_pulse_us func.

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 func counts the duration that the pin is equal to *pulse_level*. Signed-off-by: IhorNehrutsa <[email protected]> Co-Authored-By: Robert Hammelrath <[email protected]>
IhorNehrutsa · Dec 16, 2024 · dd7b953 · dd7b953
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Showing 5 changed files with 27 additions and 13 deletions.
diff --git a/docs/library/machine.rst b/docs/library/machine.rst
@@ -181,19 +181,22 @@ Miscellaneous functions
    varies by hardware (so use substring of a full value if you expect a short
    ID). In some MicroPython ports, ID corresponds to the network MAC address.
 
-.. function:: time_pulse_us(pin, pulse_level, timeout_us=1000000, /)
+.. function:: time_pulse_us(pin, pulse_level, timeout_us=1000000, wait_opposite=false, /)
 
    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 current input value of the pin is different to *pulse_level*,
-   the function first (*) waits until the pin input becomes equal to *pulse_level*,
-   then (**) times the duration that the pin is equal to *pulse_level*.
+   If *wait_opposite* is true, if the pin is initially equal to *pulse_level* then first
+   waits until the pin input becomes different from *pulse_level* (***).
+   Then if the current input value of the pin is different to *pulse_level*,
+   the function first (**) waits until the pin input becomes equal to *pulse_level*,
+   then (*) times the duration that the pin is equal to *pulse_level*.
    If the pin is already equal to *pulse_level* then timing starts straight away.
 
+   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, and -1 if there was timeout during the main measurement, marked (*)
    above. The timeout is the same for both cases and given by *timeout_us* (which
    is in microseconds).
 

diff --git a/drivers/dht/dht.c b/drivers/dht/dht.c
@@ -71,16 +71,17 @@ static mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
         }
     }
 
+    #define WAIT_OPPOSITE false
     // time pulse, should be 80us
-    ticks = machine_time_pulse_us(pin, 1, 150);
+    ticks = machine_time_pulse_us(pin, 1, 150, WAIT_OPPOSITE);
     if ((mp_int_t)ticks < 0) {
         goto timeout;
     }
 
     // time 40 pulses for data (either 26us or 70us)
     uint8_t *buf = bufinfo.buf;
     for (int i = 0; i < 40; ++i) {
-        ticks = machine_time_pulse_us(pin, 1, 100);
+        ticks = machine_time_pulse_us(pin, 1, 100, WAIT_OPPOSITE);
         if ((mp_int_t)ticks < 0) {
             goto timeout;
         }

diff --git a/extmod/machine_pulse.c b/extmod/machine_pulse.c
@@ -30,8 +30,14 @@
 
 #if MICROPY_PY_MACHINE_PULSE
 
-MP_WEAK mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us) {
+MP_WEAK mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us, bool wait_opposite) {
     mp_uint_t start = mp_hal_ticks_us();
+    while (wait_opposite && (mp_hal_pin_read(pin) == pulse_level)) {
+        if ((uint64_t)(mp_hal_ticks_us() - start) >= (uint64_t)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;
@@ -56,10 +62,14 @@ static mp_obj_t machine_time_pulse_us_(size_t n_args, const mp_obj_t *args) {
     if (n_args > 2) {
         timeout_us = mp_obj_get_int(args[2]);
     }
-    mp_uint_t us = machine_time_pulse_us(pin, level, timeout_us);
-    // May return -1 or -2 in case of timeout
+    bool wait_opposite = false;
+    if (n_args > 3) {
+        wait_opposite = mp_obj_is_true(args[3]);
+    }
+    mp_uint_t us = machine_time_pulse_us(pin, level, timeout_us, wait_opposite);
+    // 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_pulse_us_obj, 2, 3, machine_time_pulse_us_);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_pulse_us_obj, 2, 4, machine_time_pulse_us_);
 
 #endif
diff --git a/extmod/modmachine.h b/extmod/modmachine.h
@@ -244,7 +244,7 @@ uintptr_t MICROPY_MACHINE_MEM_GET_WRITE_ADDR(mp_obj_t addr_o, uint align);
 
 NORETURN mp_obj_t machine_bootloader(size_t n_args, const mp_obj_t *args);
 void machine_bitstream_high_low(mp_hal_pin_obj_t pin, uint32_t *timing_ns, const uint8_t *buf, size_t len);
-mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us);
+mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us, bool wait_opposite);
 
 MP_DECLARE_CONST_FUN_OBJ_0(machine_unique_id_obj);
 MP_DECLARE_CONST_FUN_OBJ_0(machine_reset_obj);

diff --git a/ports/esp8266/modmachine.c b/ports/esp8266/modmachine.c
@@ -329,7 +329,7 @@ MP_DEFINE_CONST_OBJ_TYPE(
     );
 
 // Custom version of this function that feeds system WDT if necessary
-mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us) {
+mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us, bool wait_opposite) {
     int nchanges = 2;
     uint32_t start = system_get_time(); // in microseconds
     for (;;) {