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I'm currently developping (improving) an Octoprint plugin that is used to control servo motors with the pigpio library. I always thought that I had to initialize the servos at the start of the code by sending a pulsewidth of 0 μs, doing pi.set_servo_pulsewidth(pin, 0) on Python http://abyz.me.uk/rpi/pigpio/python.html#set_servo_pulsewidth .

My problem is that I need to read the actual angular position of the servo on start. And after "initializing" it, I would get '0' after settings the pulsewidth to 0 by using pi.get_servo_pulsewidth(pin) on the same GPIO.

After reading the doc, I think that I just don't need at all to initialize the servo, and I could get the actual pulsewidth at the start of the code....

Does anybody could answer me by experience or try it please ? I don't have any Raspberry or servo motor where I am currently.

Thanks

1 Answer 1

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Servos move to a commanded position when given a valid pulse width. A pulse width of 0 is used to tell pigpio to stop sending servo pulses.

The get_servo_pulsewidth() function tells you the last commanded position. It tells you nothing about the current servo position.

Most hobby servos provide no method of discovering the position. You need a special servo or additional hardware to find a servo's position.

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  • Never knew such things existed. Just been reading up on the and resistive and Hall effect versions - not cheap to say the least.
    – user115418
    Nov 13, 2020 at 22:55
  • Thank you very much for this answer. I hopefully have the solution to send a "autohome" position on server startup, but this movement will be harsh... After this, I can easily track the current position. Happy day!
    – Franfran
    Nov 14, 2020 at 1:21

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