Gpiod
Revision as of 10:37, 7 January 2022 by RadxaYuntian (Talk | contribs)
Contents
Use gpiod to control GPIO pins
Traditionally GPIO pins are exposed by Linux kernel under /sys/class/gpio namespace. However, this interface has been deprecated since version 4.8. The replacement is a C binding called libgpiod, along with a set of user land tools called gpiod.
In this guide we will talk about some common usage of gpiod so you can start incorporate them in your projects.
Installation
Run following command under Debian/Ubuntu:
sudo apt update sudo apt install gpiod -y
List available GPIO controller
radxa@radxa-zero2:~$ sudo gpioinfo
gpiochip0 - 85 lines:
line 0: "PIN_27" unused input active-high
line 1: "PIN_28" unused input active-high
line 2: "PIN_7" unused input active-high
line 3: "PIN_11" unused input active-high
line 4: "PIN_13" unused input active-high
line 5: "PIN_14" unused input active-high
line 6: "PIN_18" unused input active-high
line 7: "PIN_40" unused input active-high
line 8: unnamed unused input active-high
line 9: unnamed unused input active-high
line 10: unnamed unused input active-high
line 11: unnamed unused input active-high
line 12: unnamed unused input active-high
line 13: unnamed unused input active-high
line 14: unnamed unused input active-high
line 15: unnamed unused input active-high
line 16: unnamed unused input active-high
line 17: unnamed unused input active-high
line 18: unnamed unused input active-high
line 19: unnamed unused input active-high
line 20: "PIN_19" unused input active-high
line 21: "PIN_21" unused input active-high
line 22: "PIN_24" unused input active-high
line 23: "PIN_23" unused input active-high
line 24: unnamed unused input active-high
line 25: unnamed unused input active-high
line 26: unnamed unused input active-high
line 27: unnamed unused input active-high
line 28: unnamed unused input active-high
line 29: unnamed unused input active-high
line 30: unnamed unused input active-high
line 31: unnamed unused input active-high
line 32: unnamed unused input active-high
line 33: unnamed unused input active-high
line 34: unnamed unused input active-high
line 35: unnamed unused input active-high
line 36: unnamed unused input active-high
line 37: unnamed "reset" output active-low [used]
line 38: unnamed unused input active-high
line 39: unnamed unused input active-high
line 40: unnamed unused input active-high
line 41: unnamed unused input active-high
line 42: unnamed unused input active-high
line 43: unnamed unused input active-high
line 44: unnamed unused input active-high
line 45: unnamed unused input active-high
line 46: unnamed unused input active-high
line 47: unnamed "cd" input active-low [used]
line 48: "PIN_36" unused input active-high
line 49: "PIN_32" unused input active-high
line 50: "PIN_12" unused input active-high
line 51: "PIN_35" unused input active-high
line 52: unnamed unused input active-high
line 53: unnamed unused input active-high
line 54: "PIN_38" unused input active-high
line 55: unnamed unused input active-high
line 56: unnamed unused input active-high
line 57: unnamed unused input active-high
line 58: unnamed unused input active-high
line 59: unnamed unused input active-high
line 60: unnamed unused input active-high
line 61: unnamed "green:status" output active-high [used]
line 62: "PIN_31" unused input active-high
line 63: "PIN_3" unused input active-high
line 64: "PIN_25" unused input active-high
line 65: unnamed unused input active-high
line 66: unnamed unused input active-high
line 67: unnamed unused input active-high
line 68: unnamed unused input active-high
line 69: unnamed unused input active-high
line 70: unnamed unused input active-high
line 71: unnamed "reset" output active-low [used]
line 72: unnamed unused input active-high
line 73: unnamed unused input active-high
line 74: unnamed unused input active-high
line 75: unnamed unused input active-high
line 76: unnamed unused input active-high
line 77: unnamed unused input active-high
line 78: unnamed unused input active-high
line 79: unnamed unused input active-high
line 80: unnamed unused input active-high
line 81: unnamed unused input active-high
line 82: unnamed "shutdown" output active-high [used]
line 83: unnamed unused input active-high
line 84: unnamed unused input active-high
gpiochip1 - 15 lines:
line 0: "PIN_8" unused input active-high
line 1: "PIN_10" unused input active-high
line 2: unnamed unused input active-high
line 3: unnamed "power" input active-low [used]
line 4: unnamed unused output active-high
line 5: unnamed unused input active-high
line 6: unnamed unused input active-high
line 7: "PIN_29" unused input active-high
line 8: "PIN_33" unused input active-high
line 9: "PIN_37" unused input active-high
line 10: unnamed unused input active-high
line 11: unnamed unused output active-high
line 12: unnamed unused input active-high
line 13: unnamed unused input active-high
line 14: unnamed unused input active-high
Convert 40-pin header number to gpiod device number
radxa@radxa-zero2:~$ sudo gpiofind PIN_8 gpiochip1 0
Read GPIO pin level
radxa@radxa-zero2:~$ sudo gpioget $(sudo gpiofind PIN_8) 1
Set GPIO pin level
radxa@radxa-zero2:~$ sudo gpioset $(sudo gpiofind PIN_8)=0 radxa@radxa-zero2:~$ sudo gpioset $(sudo gpiofind PIN_8)=1
Watch GPIO level change
You need to specify either -r for rising edge events or -f for falling edge events, but not both.
radxa@radxa-zero2:~$ sudo gpiomon -f $(sudo gpiofind PIN_37) event: FALLING EDGE offset: 0 timestamp: [ 3882.313792858]
A simple GPIO test script based on gpiod
Here is a sample script that uses gpiod to test all onboard GPIO pins.