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GPIO Control

Note

Please use WalnutPi OS v2.3 or above.

About Pin Numbering​

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

gpio pins

gpio_pins

For detailed operations, please refer to: GPIO Command-Line Operations. This will not be repeated here.

Sample Code​

Here is a sample program: when the button on the WalnutPi board is pressed, the LED turns on; when released, the LED turns off.

#include <stdio.h>
#include <unistd.h>
#include "gpio.h" // GPIO control library

#define KEY 41
#define LED 42
// These pin numbers are 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 to the compilation command. The following command compiles test.c in the current directory into an executable named test:

gcc -Wall -o test test.c -lgpio

Run the compiled program. Note that you need administrator privileges to control GPIO:

sudo ./test

Geany IDE Compilation​

For instructions on using Geany IDE, refer to this tutorial: Compiling C Code on the Board

If you are using the Geany IDE that comes pre-installed with the WalnutPi desktop system, you need to make the following configuration changes.

Open Build > Set Build Commands:

c4

c4

Add -lgpio at the end of the Build command so that the GPIO library is included during compilation when you click the Build button:

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

Add sudo before the Execute command so that the program runs with administrator privileges when you click the Run button:

sudo "./%e"

Click OK to save.