Get current position of servo with MicroPython on a Raspberry Pi Pico - micropython

Question

I am running MicroPython on a Raspberry Pi Pico. I can set the position of the servo by changing the duty cycles:
from machine import Pin, PWM
servo = PWM(Pin(0))
servo.freq(50)
servo.duty_u16(1350) # sets position to 0 degrees
I may have missed something, but I have read through the docs and couldn't find any way to read the current position of the servo. Is there any way to do this?

Answer 1

Most servos do not provide any sort of position information. You know what the position is because you set it. You can write code that will keep track of this value for you. For example, something like:
from machine import Pin, PWM
class Servo:
min_duty = 40
max_duty = 1115
def __init__(self, pin):
servo = PWM(Pin(pin))
servo.freq(50)
self.servo = servo
self.setpos(90)
def setpos(self, pos):
'''Scale the angular position to a value between self.min_duty
and self.max_duty.'''
if pos < 0 or pos > 180:
raise ValueError(pos)
self.pos = pos
duty = int((pos/180) * (self.max_duty - self.min_duty) + self.min_duty)
self.servo.duty(duty)
You would use the Servo class like this:
>>> s = Servo(18)
>>> s.pos
90
>>> s.setpos(180)
>>> s.pos
180
>>> s.setpos(0)
>>> s.pos
0
>>>
In your question, you have:
servo.duty_u16(1350)
I'm suspicious of this value: at 50Hz, the duty cycle is typically between 40 and 115 (+/1 some small amount at either end), corresponding to ≈ 1ms (duty=40) to 2ms (duty=115).