CM3-Panel-7-basic technical documentation

Using pigpiod daemon to manage the GPIO on CM3-Panel

This article explains how to use the GPIO lines available on EXP1 and EXP2 connector of CM3-Panel-7-basic using Python3 and pigpio library

Install pigpiod

sudo apt update
sudo apt install pigpiod
sudo apt install python3-pigpio

Launch the pigpiod daemon at startup by editing rc.local:

sudo nano /etc/rc.local

Add this line

/usr/bin/pgpiod
exit 0

Examples

Simple gpio input

import pigpio

gpio=pigpio.pi()

gpio.set_mode(28,pigpio.INPUT)
gpio.set_mode(29,pigpio.INPUT)


gpio.set_pull_up_down(28, pigpio.PUD_UP)
gpio.set_pull_up_down(29, pigpio.PUD_UP)

print(gpio.read(28))
print(gpio.read(29))

Simple gpio output

This example works well with the GPIO lines:

  • 25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41

and not with:

  • 22 works but change the LCD backlight state
  • 23 works but is used also for the led of Raspicam
  • 24 works but is used also for shutdown line of Raspicam
  • 42 used by the int line of touch screen
  • 43 used by the reset line of display
  • 44 and 45 are used for the I2C bus used by the touch screen and Raspicam

Example

import pigpio
import time

LED=27

gpio=pigpio.pi()
gpio.set_mode(LED,pigpio.OUTPUT)

while True:
    gpio.write(LED,0)
    time.sleep(1)
    gpio.write(LED,1)
    time.sleep(1)

Callback function on GPIO changes with steady filter

import pigpio
import time

def gpio_28(gpio, level, tick):
    print("GPIO 28 low")
    print(gpio, level, tick)
    return  

def gpio_29(gpio, level, tick):
    print("GPIO 29 low")
    print(gpio, level, tick)
    return  

gpio=pigpio.pi()

gpio.set_mode(28,pigpio.INPUT)
gpio.set_mode(29,pigpio.INPUT)


gpio.set_glitch_filter(28,50000)
gpio.set_glitch_filter(29,50000)

gpio.set_pull_up_down(28, pigpio.PUD_UP)
gpio.set_pull_up_down(29, pigpio.PUD_UP)

gpio.callback(28,pigpio.FALLING_EDGE,gpio_28)
gpio.callback(29,pigpio.FALLING_EDGE,gpio_29)

while True:
    time.sleep(1)
    print("Loop")

Links

CM3-Panel-7-basic technical documentation