/
rotary_encoder.py
112 lines (75 loc) · 2.65 KB
/
rotary_encoder.py
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#!/usr/bin/env python
import pigpio
class decoder:
"""Class to decode mechanical rotary encoder pulses."""
def __init__(self, pi, gpioA, gpioB, callback):
"""
Instantiate the class with the pi and gpios connected to
rotary encoder contacts A and B. The common contact
should be connected to ground. The callback is
called when the rotary encoder is turned. It takes
one parameter which is +1 for clockwise and -1 for
counterclockwise.
EXAMPLE BELOW
"""
self.pi = pi
self.gpioA = gpioA
self.gpioB = gpioB
self.callback = callback
self.levA = 0
self.levB = 0
self.lastSeq = 2
self.lastGpio = None
self.pi.set_mode(gpioA, pigpio.INPUT)
self.pi.set_mode(gpioB, pigpio.INPUT)
self.pi.set_pull_up_down(gpioA, pigpio.PUD_UP)
self.pi.set_pull_up_down(gpioB, pigpio.PUD_UP)
self.cbA = self.pi.callback(gpioA, pigpio.EITHER_EDGE, self._pulse)
self.cbB = self.pi.callback(gpioB, pigpio.EITHER_EDGE, self._pulse)
def _pulse(self, gpio, level, tick):
"""
Decode the rotary encoder pulse.
+---------+ +---------+ 0
| | | |
A | | | |
| | | |
+---------+ +---------+ +----- 1
+---------+ +---------+ 0
| | | |
B | | | |
| | | |
----+ +---------+ +---------+ 1
"""
if gpio == self.gpioA:
self.levA = level
else:
self.levB = level;
if gpio != self.lastGpio: # debounce
self.lastGpio = gpio
seq = (self.levA^self.levB) + (self.levA<<1)
if ((seq-self.lastSeq==1)or(seq-self.lastSeq==-3)):
self.callback(1)
elif ((seq-self.lastSeq==-1)or(seq-self.lastSeq==3)):
self.callback(-1)
self.lastSeq=seq
def cancel(self):
"""
Cancel the rotary encoder decoder.
"""
self.cbA.cancel()
self.cbB.cancel()
#EXAMPLE:
if __name__ == "__main__":
import time
import pigpio
import rotary_encoder
pos = 0
def callback(way):
global pos
pos += way
print("pos={}".format(pos))
pi = pigpio.pi()
decoder = rotary_encoder.decoder(pi, 9, 11, callback)
time.sleep(5)
decoder.cancel()
pi.stop()