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extmod/machine_pulse: Optimise time_pulse_us for code size.

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This implementation is based on the esp8266 custom implementation, and
further optimised for size and accuracy.

Testing on PYBD_SF2 and RPI_PICO2_W shows that it is at least as good as
the original implementation in performance.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George
2025-05-23 12:56:12 +10:00
parent 5676b45cbb
commit ef21ade602
1 changed files with 25 additions and 10 deletions
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35
extmod/machine_pulse.c
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@@ -31,19 +31,34 @@
#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_uint_t nchanges = 2;
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)-2;
for (;;) {
// Sample ticks and pin as close together as possible, and always in the same
// order each time around the loop. This gives the most accurate measurement.
mp_uint_t t = mp_hal_ticks_us();
int pin_value = mp_hal_pin_read(pin);
if (pin_value == pulse_level) {
// Pin is at desired value. Flip desired value and see if we are done.
pulse_level = 1 - pulse_level;
if (--nchanges == 0) {
return t - start;
}
start = t;
} else {
// Pin hasn't changed yet, check for timeout.
mp_uint_t dt = t - start;
if (dt >= timeout_us) {
return -nchanges;
}
// Allow a port to perform background task processing if needed.
#ifdef MICROPY_PY_MACHINE_TIME_PULSE_US_HOOK
MICROPY_PY_MACHINE_TIME_PULSE_US_HOOK(dt);
#endif
}
}
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_pulse_us_(size_t n_args, const mp_obj_t *args) {