GPIO (Class)

Quick Details

How Does it Work?

The GPIO pins on the BeagleBone can be controlled through special files located in the /sys/class/gpio folder. This folder contains a bunch of subdirectories, each one referring to a single GPIO pin. Rather than using names such as P9_14, the folders are named according to each pin's absolute number. You can check the BeagleBone manual for a table of absolute pin numbers.

Setting the Direction

To set the direction (input or output) of the pin, you can write to the GPIO pin's direction file:

• To set the pin as output: echo out > direction
• To set the pin as input: echo in > direction

Setting the Value

To set the value of the pin during output mode, you can write to the pin's value file:

• To set the output to LOW: echo 0 > value
• To set the output to HIGH: echo 1 > value

Getting the Value

To read the value of the pin, you can read from the pin's value file:

• To set the output to LOW: cat value
• To set the output to HIGH: cat value

Exporting Pins

If the necessary pin is not available in the gpio folder, you may be able to enable it by writing the pin number to the export file. After you are done, you should unexport the pin by writing the pin number to the unexport file.

Functions

GPIO(const char *key);

GPIOMode SetMode(GPIOMode mode);

GPIOValue DigitalRead();

GPIOValue DigitalWrite(GPIOValue value);