My platform is orin, we use external PWM trigger to synchronize between multiple lenses, the lens is controlled by the pulse width to control the exposure. The commands to control exposure are as follows:
import RPi.GPIO as GPIO
import time
output_pins = {
'JETSON_XAVIER': 18,
'JETSON_NANO': 33,
'JETSON_NX': 33,
'CLARA_AGX_XAVIER': 18,
'JETSON_TX2_NX': 32,
'JETSON_ORIN': 18,
'JETSON_ORIN_NX': 33,
'JETSON_ORIN_NANO': 33
}
output_pin = output_pins.get(GPIO.model, None)
if output_pin is None:
raise Exception('PWM not supported on this board')
print(output_pin)
def main():
# Pin Setup:
# Board pin-numbering scheme
GPIO.setmode(GPIO.BOARD)
# set pin as an output pin with optional initial state of HIGH
GPIO.setup(output_pin, GPIO.OUT, initial=GPIO.HIGH)
p = GPIO.PWM(output_pin, 10)
val = 100
incr = 5
p.start(val)
print("PWM running. Press CTRL+C to exit.")
try:
while True:
time.sleep(0.25)
#if val >= 100:
# incr = -incr
#if val <= 0:
# incr = -incr
#val += incr
#p.ChangeDutyCycle(val)
finally:
p.stop()
GPIO.cleanup()
if __name__ == '__main__':
main()
We will start the simple pwm.py script first, and then use the command to control the exposure. But I ran into a problem when I set the value above 99800000 and there was no trigger signal. May I ask why?
I’ve checked with internal.
The clock rate of parent clock (pllp_out0) for pwm5 is 408M, which results in max rate at 1.5M (clk_rate / (256 * 1))
You could find more details in TRM document (PWM->Programming Guidelines).
Please configure pwm period to 1.5M and try different value for duty cycle.
According to the formula, it is not clear why there is a limit of 200000~99800000. Because the project requires that the hardware trigger needs to be triggered ten times per second, so the period here can only be set to 100000000, and I hope that the duty cycle can be set to 99.99% on this basis. There is also how I can determine the current PWM5 clock size.
Do you mean 10Hz? Why you need to configure the period to 100M?
It is relating to the clock accuracy.
Please just configure the /sys/class/pwm/pwmchip2/pwm0/period to 1000000 and try with different duty cycle (0%-100%)
Thank you very much for your patient reply. I have tried the method you mentioned, and his working range is between 2000 and 998000, which is a hundred times smaller than the previous phenomenon.
Sorry that I’m not clear about these relationship.
Could you help to clarify and explain more details? Why 10Hz (10 times/second) results period to be 100M?
Okay, you’re not quite understanding what I’m saying, so let’s ignore the frequency. This period is measured in nanoseconds, and if I set the period to 100000000 ns, that means I have 10 cycles per second. The number of cycles is the trigger frequency I need.
What do you mean about “not work”?
Could you configure this value w/o modifying the parent clock for pwm0?
Or there’s no waveform output when you configure this value.
