Pigpio not calling Callback for first rising or falling edge

Question

I have some sample code (taken out of my larger program) that regularly (but not always) missing the first rising edge:

#!/usr/bin/python
import pigpio, time

def callback(g, l, t):
  print("Callback trigger "+ str(g)+ " " +str(l)+ " " +str(t))

pi = pigpio.pi()
if not pi.connected:  # Check connected
  print("Not connected to PIGPIO Daemon")
else:
  print("Connected to PIGPIO Daemon")
  pinStartGate = 20

  pi.set_mode(pinStartGate, pigpio.INPUT)
  pi.set_pull_up_down(pinStartGate, pigpio.PUD_DOWN)  
  pi.set_noise_filter(pinStartGate, 50000, 50000)  # Debounce switch
  # pi.set_glitch_filter(pinStartGate, 50000)  # Debounce switch

  cb1 = pi.callback(pinStartGate, pigpio.FALLING_EDGE, callback)


while(True):
  print("Direct trigger" + str(pi.read(pinStartGate)))
  time.sleep(1)

running this, with pin 20 initially not connected, and then connecting to 3.3v or 5v gives:

Direct trigger0
Direct trigger0
Direct trigger1
Direct trigger1
Direct trigger0
Direct trigger0
Callback trigger 20 0 2414139526
Direct trigger1
Direct trigger1
Direct trigger0
Direct trigger0
Callback trigger 20 0 2418808728
Direct trigger1
Direct trigger1

You can see that the first trigger, does not trigger the Callback.

I am also suprised by the way around that I need to use 'pigpio.FALLING_EDGE' as in electrical terms it is the Rising edge that I am triggering based upon (going from not connected, so pigpio.PUD_DOWN = 0v to externally connected to 3.3v or 5v?

Running Raspbian Stretch, Python 3.5.3 and pigpio v64

Thanks very much Kevin

Answer 1

pigpio reports level changes via Python callbacks.

NEVER connect more than 3V3 to a Pi GPIO (you will eventually destroy the GPIO and then the Pi).

I would not use the noise filter for switch debounce. If you suffer from switch bounce use the glitch filter.

Your output does look odd. I suggest while testing you change the callback to either edge and print out pi.get_current_tick() in the direct read so we can see how the events are interleaved.

#!/usr/bin/python

import pigpio, time

def callback(g, l, t):
  print("Callback " + str(l) + " " + str(t))

pi = pigpio.pi()
if not pi.connected:
   exit()

pin = 20

pi.set_mode(pin, pigpio.INPUT)
pi.set_pull_up_down(pin, pigpio.PUD_DOWN)  

cb1 = pi.callback(pin, pigpio.EITHER_EDGE, callback)

while True:
  print("Direct " + str(pi.read(pin)) + " " + str(pi.get_current_tick()))
  time.sleep(1)

This gave the following output when I set GPIO 20 up/down with pigs in another terminal window.

Direct 0 3068153032
Direct 0 3069154220
Direct 0 3070156011
Callback 1 3070974455
Direct 1 3071157718
Direct 1 3072159517
Direct 1 3073161135
Direct 1 3074162919
Direct 1 3075164671
Direct 1 3076165956
Direct 1 3077167750
Callback 0 3077950413
Direct 0 3078169474
Direct 0 3079171260
Direct 0 3080173127
Direct 0 3081174929
Direct 0 3082176712
Direct 0 3083178524
Direct 0 3084180331
Callback 1 3084236329
Direct 1 3085182138
Direct 1 3086183936
Direct 1 3087185751
Direct 1 3088187540
Direct 1 3089189351
Callback 0 3089332637
Direct 0 3090191219
Direct 0 3091192091