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IO Control

Note

Please use WalnutPi OS v2.3 or above.

About Pin Numbering​

Run the following command to view the status of each pin. In subsequent programming, use the Physical numbers from this table to refer to the pins.

gpio pins

gpio_pins

For detailed operation instructions, please refer to: GPIO Command Operations section. This will not be repeated here.

Example Code​

Here is an example: pressing the button on the WalnutPi development board turns on the LED, and releasing it turns off the LED.

#include <stdio.h>
#include <unistd.h>
#include "gpio.h" // Library for controlling GPIO

#define KEY 41
#define LED 42
// These two pin numbers can be obtained using the gpio pins command

int main()
{
    pin_set_mode(LED, OUTPUT); 
    pin_set_mode(KEY, INPUT); 
    pin_set_pullUpDn(KEY, PULL_UP); // Enable internal pull-up
    while (1)
    {
        if (pin_read(KEY) == 0)
            pin_write(LED, 1);
        else
            pin_write(LED, 0);
    }
    return 0;
}

Command Line Compilation and Execution​

To compile the code, since the GPIO library exists as a dynamic library, you need to add -lgpio during compilation. The following command compiles the test.c file in the current directory into the executable test.

gcc -Wall -o test test.c -lgpio

Run the compiled program. Note that administrator privileges are required to control GPIO:

sudo ./test

Geany IDE Compilation​

For how to use Geany IDE, refer to this tutorial: Compiling C Code on the Development Board

If you are using the Geany IDE that comes with the WalnutPi desktop system, you need to make some settings.

Open Build--Set Build Commands:

c4

c4

Add -lgpio at the end of the Build command, so that when you click the build button in the software, the GPIO library will also participate in the compilation process:

gcc -Wall -o "%e" "%f" -lgpio

Add sudo before the Execute command, so that when you click the run button in the software, it will run with administrator privileges:

sudo "./%e"

Click OK to save.