Linux is a popular operating system used in many devices, including those based on ARM architecture. One of the key features of Linux is its ability to control the General Purpose Input/Output (GPIO) pins on ARM-based devices. In this article, we will explore the basics of Linux drivers for ARM GPIO and pin control.
GPIO pins are versatile pins that can be configured as either input or output pins. They are commonly used to interface with external devices such as sensors, buttons, LEDs, and more. Linux provides a framework for controlling these GPIO pins through device drivers.
Device Tree
In Linux, the Device Tree is a data structure that describes the hardware components of a device. It provides a way for the operating system to understand the hardware configuration and initialize the necessary drivers. The Device Tree contains information about the GPIO pins available on the device.
GPIO Subsystem
The GPIO subsystem in Linux provides an interface for controlling GPIO pins. It allows users to set the direction of a pin as either input or output, read the value of an input pin, and write a value to an output pin. The GPIO subsystem is accessed through the /sys/class/gpio directory.
Using GPIOs
To use a GPIO pin, you first need to export it. This makes the pin available for use by creating a corresponding directory in the /sys/class/gpio directory. You can export a pin by writing its number to the export file:
echo <pin_number> > /sys/class/gpio/export
Once exported, you can set the direction of the pin by writing either in or out to the direction file:
echo <in/out> > /sys/class/gpio/gpio<pin_number>/direction
If the pin is set as an output, you can write a value to it by writing 0 or 1 to the value file:
echo <0/1> > /sys/class/gpio/gpio<pin_number>/value
If the pin is set as an input, you can read its value by reading the value file:
cat /sys/class/gpio/gpio<pin_number>/value
Pin Control Subsystem
In addition to GPIO pins, some ARM-based devices also have pins that can be used for other purposes, such as I2C, SPI, or UART. The Pin Control subsystem in Linux provides an interface for controlling these pins.
Conclusion
Understanding Linux drivers for ARM GPIO and pin control is essential for working with GPIO pins and other configurable pins on ARM-based devices. With the GPIO and Pin Control subsystems, you can easily configure and control these pins to interface with external devices. By utilizing the Device Tree, you can ensure that the operating system recognizes and initializes the necessary drivers for your specific hardware configuration.
| Reference | Link |
|---|---|
| Linux GPIO Documentation | https://www.kernel.org/doc/Documentation/gpio/ |
| Linux Pin Control Documentation | https://www.kernel.org/doc/Documentation/pinctrl/ |