40pin IO Development

Experiment 04 - PWM Output

Hardware Connection

Connect servo/motor/oscilloscope to IO33 (X5 mainboard supports IO32 and IO33 PWM output).

Software Operation

Enter the user home directory and run:

cd user
sudo python3 ./PWM_out.py

Terminal as shown:

You can see: the initial duty cycle is 25%, then increases by 5% every 0.25 seconds, reaches 100%, then decreases by 5% every 0.25 seconds.

#!/usr/bin/env python3
import sys
import signal
import Hobot.GPIO as GPIO
import time

def signal_handler(signal, frame):
    sys.exit(0)

# PWM capable pins: 32 and 33, ensure the pin is not used by other functions
output_pin = 33

GPIO.setwarnings(False)

def main():
    # Pin Setup:
    # Board pin-numbering scheme
    GPIO.setmode(GPIO.BOARD)
    # Supported frequency range: X3: 48KHz ~ 192MHz X5: 0.05HZ ~ 100MHZ
    p = GPIO.PWM(output_pin, 48000)
    # Initial duty cycle 25%, increase 5% every 0.25s, then decrease after 100%
    val = 25
    incr = 5
    p.ChangeDutyCycle(val)
    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__':
    signal.signal(signal.SIGINT, signal_handler)
    main()