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GPIO usage

GPIOD Introduction​

The GPIO sysfs interface has been deprecated since Linux 4.8. Userspace should instead use libgpiod to interact with GPIO character devices.

Key features​

  • Easy to use: libgpiod provides a simple API that makes controlling and operating GPIO devices easy to understand. Developers only need to understand basic GPIO concepts and function interfaces to use it.
  • Efficient Event Listening: libgpiod provides functionality for asynchronous event listening, such as waiting for GPIO state changes. This allows developers to implement efficient event-driven applications.
  • GPIO specification support: libgpiod provides support for different GPIO specifications and numbering methods, including GPIO numbering and physical pin numbering.

Command Line Tools​

libgpiod provides a variety of command line tools, for viewing and control GPIO devices.

gpiodetect​

List all GPIO controllers in the system:

radxa：/$ gpiodetect
gpiochip0 [gpio0] (32 lines)
gpiochip1 [gpio1] (32 lines)
gpiochip2 [gpio2] (32 lines)
gpiochip3 [gpio3] (32 lines)
gpiochip4 [gpio4] (32 lines)

gpioinfo​

Display GPIO device information:

radxa：/$ 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_15"       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
...
info

When using the 'libgpiod' command-line tool to control GPIO, ensure that GPIO is in an unused state

gpioget​

Set GPIO to input mode and obtain the input status of GPIO:

radxa：/$ gpioget gpiochip0 0
1

gpioset​

Set GPIO to output mode and set the output status of GPIO:

radxa：/$ gpioset gpiochip0 0=1

gpiomon​

Monitor GPIO events:

radxa：/$ gpiomon gpiochip0 0
(GPIO event output)

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