Using libgpiod to detect input events

Mon, 17 May 2021 00:00:00 +0000

Using libgpiod to detect input events

One of the most fundamental requirements for GPIO is the ability to execute user defined code when an external event has happened. This is typically done when a GPIO pin, configured as an input, changes from high-to-low, or low-to-high. In this case we detect on the falling edge or rising edge of this pin change. For example a sensor we communicate through GPIO has data ready. In the micro-controller world this is called as an interrupt where the CPU will change it program counter and handle the interrupt. The interrupt makes sense when we have no Operating System. In the case of Linux and the Raspberry Pi it’s not an interrupt but considered an event as we likely have in interrupt deep inside the kernel code, however, we’re several levels of abstraction past this. Unix has the “Universal File Model” so this input pin is mapped to a file. With Unix we have many multiple ways to know if “events” have happened to this file. Examples of events are that the file is ready for reading, writing, or other events have happened.

The new GPIO Interface on the Raspberry PI: libgpiod

Sun, 02 May 2021 00:00:00 +0000

The new GPIO Interface on the Raspberry PI: libgpiod

Allegedly, The GPIO Sysfs Interface is deprecated. The deprecated Sysfs would interact with GPIO using the /sys/class/gpio pseudo-filesytem. The Application Binary Interface - ABI - provides a character device based device driver and tools. The ABI is the new way to interact with GPIO on the Raspberry Pi. I really don’t like the name ABI, as it’s WAY too generic of a name. Rather, I believe the proper name for this project is libgpiod.

Gpio on Lloyd Rochester's Geek Blog

Using libgpiod to detect input events

Using libgpiod to detect input events

The new GPIO Interface on the Raspberry PI: libgpiod

The new GPIO Interface on the Raspberry PI: libgpiod