Beginners • Specific number of nanosecond pulses generation

Code:

# Starting point: https://raspberrypi.stackexchange.com/a/113709/131225import pigpio # https://github.com/joan2937/pigpiofrom time import sleepfrom time import perf_counter_nsfrom timeit import default_timer as timerimport ctypeslibc = ctypes.CDLL('libc.so.6')def usleep(seconds):libc.usleep(int(seconds*1e6))def spinwait_us(seconds):target = perf_counter_ns() + seconds*1e6 * 1000while perf_counter_ns() < target:passdef brute_force_sleep(seconds):start = timer()while timer()-start < seconds:passclass PulseGenerator:PWM_FREQ = int(1000) # PWMfreq 1-125e6, http://abyz.me.uk/rpi/pigpio/python.html#PWMfreq, don't make the PWM frequency too high because it could fail in generating only one pulse, as we rely on the software to turn off the PWM in the middle of one cycle in order to get a single pulse.MAGIC_FACTOR = 1e6 # The factor `1e6` comes from http://abyz.me.uk/rpi/pigpio/python.html#PWMdutydef __init__(self, output_pin:int):self._output_pin = output_pinself._max_pulse_duration = PulseGenerator.PWM_FREQ**-1/2self._min_pulse_duration = 1/PulseGenerator.MAGIC_FACTOR/PulseGenerator.PWM_FREQ # This will happen when the "duty cycle" parameter is 1.self.PI = pigpio.pi()self.PI.hardware_PWM(self._output_pin, PulseGenerator.PWM_FREQ, 0) # Start the PWM hardware but outputing nothing (duty cycle = 0).def generate_pulses(self, pulse_duration:float, n_pulses:int):if pulse_duration > self._max_pulse_duration:raise ValueError(f'Pulse duration cannot be higher than {self._max_pulse_duration:.2e}, received {pulse_duration:.2e}. ')if pulse_duration < self._min_pulse_duration:raise ValueError(f'Pulse duration cannot be lower than {self._min_pulse_duration:.2e}, received {pulse_duration:.2e}. ')duty_cycle = int(PulseGenerator.MAGIC_FACTOR*pulse_duration*PulseGenerator.PWM_FREQ)sleep_time = 1/PulseGenerator.PWM_FREQ*(n_pulses-.1)self.PI.hardware_PWM(self._output_pin, PulseGenerator.PWM_FREQ, duty_cycle)brute_force_sleep(sleep_time) # We have faith that the program will make it, but this could fail if the processor is too busy.self.PI.hardware_PWM(self._output_pin, PulseGenerator.PWM_FREQ, 0) # The only way I found so far of stopping the PWM, setting a duty cycle of 0.if __name__ == '__main__':pulse_generator = PulseGenerator(12)while True:pulse_generator.generate_pulses(pulse_duration=100e-9, n_pulses=5)