CM3-Panel-7-basic technical documentation Buy

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")