// Mimicking Arduino's pulseIn function
// return how long it takes a pin to go from HIGH to LOW or LOW to HIGH
static uint32_t ppd42ns_pulse_in(const ppd42ns_context dev,
bool high_low_value)
{
assert(dev != NULL);
// we run for no more than 1 second at a time
upm_clock_t max_time;
upm_clock_t pulse_time;
uint32_t total_pulse_time = 0;
upm_clock_init(&max_time);
bool pin_level;
bool is_timing = false;
do {
pin_level = (bool)mraa_gpio_read(dev->gpio);
if (!is_timing && pin_level == high_low_value)
{
// level is desired level, but not currently timing
upm_clock_init(&pulse_time);
is_timing = true;
}
else if (is_timing && pin_level != high_low_value)
{
// we started timing, but level changed
total_pulse_time += upm_elapsed_us(&pulse_time);
is_timing = false;
}
else
{
// not timing and/or level is not equal to desired level
// so we "wait".
upm_delay_us(10);
}
} while (upm_elapsed_ms(&max_time) < 1000); // 1 second
if (is_timing)
{
// if we were still timing when the loop expired, add the
// accumulated time.
total_pulse_time += upm_elapsed_us(&pulse_time);
}
return total_pulse_time;
}
void upm_delay_us(unsigned int time)
{
if (time <= 0)
time = 1;
#if defined(UPM_PLATFORM_LINUX)
struct timespec delay_time;
delay_time.tv_sec = time / 1000000;
delay_time.tv_nsec = (time % 1000000) * 1000;
// here we spin until the delay is complete - detecting signals
// and continuing where we left off
while (nanosleep(&delay_time, &delay_time) && errno == EINTR)
; // loop
#elif defined(UPM_PLATFORM_ZEPHYR)
# if KERNEL_VERSION_MAJOR == 1 && KERNEL_VERSION_MINOR >= 6
// we will use a upm_clock to do microsecond timings here as k_timer has
// only a millisecond resolution. So we init a clock and spin.
upm_clock_t timer;
upm_clock_init(&timer);
while (upm_elapsed_us(&timer) < time)
; // spin
# else
struct nano_timer timer;
void *timer_data[1];
nano_timer_init(&timer, timer_data);
nano_timer_start(&timer, USEC(time) + 1);
nano_timer_test(&timer, TICKS_UNLIMITED);
# endif
#endif
}
