Use rpi.gpio for servo control

[Iain-S]

~Using gpiozero seemed to crash the Pi so~ we could switch to RPi.GPIO. The following is known to work but it doesn't seem to support hardware PWM (so is pretty hard to control).

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)
GPIO.setup(37, GPIO.OUT)

p = GPIO.PWM(37, 50)
p.start(5)
p.start(7)
p.start(10)

for i in range(11):
  p.ChangeDutyCycle(5+i*0.5)
  sleep(0.5)

p.stop()

Note that

1. We are using GPIO.BOARD numbering so physical pin 37 is GPIO pin 26 in the image below
2. The servo works on 50Hz freq (20ms period). 1ms on (5% of 20ms) is 0 degrees an 2ms on (10%) is 180 degrees. See here for more.

note the crash could have been from trying to turn some kind of important system pin into a Servo.

[Iain-S]

Alternatively, we could use pigpio, which does support hardware PWM.

sudo pigpiod
python

import gpiozero

s = gpiozero.Servo(13, pin_factory=gpiozero.pins.pigpio.PiGPIOFactory())
s.min()
s.mid()
s.max()
s.value = 0.9 (close to max)
s.detach()

[Iain-S]

Closing as we do want to use gpiozero after all. See comment above for code to move a Servo.

Notes:

• positive values / s.max() move the servo cog anti-clockwise (as viewed from the top of the servo looking down)
• you must start the pigpio daemon before trying to create a Servo object.