Module linux 

Opening a GPIO line on a Linux board.

On a Raspberry Pi or any Linux board a pin is a line on a GPIO chip, a device file such as /dev/gpiochip0, and a line’s number on that chip is the one a board’s pinout calls its GPIO or BCM number. output and input open one through the GPIO character device backend of pamoja-hal and hand it back as a Line, which a Switch or a Contact sits over as it would over any other pin. The language bindings open lines through the same two functions, so a relay is driven the same way from Rust, TypeScript, Python, and C#.

A line is held by one process at a time, and the kernel names the holder, which gpioinfo prints; a line held by another program or claimed by a kernel driver cannot be opened until it is let go. On Raspberry Pi OS a user in the gpio group can open lines without root.

Only Linux has the GPIO character device. Everywhere else this module still builds and Line still names a type, but opening a line returns OpenError::Unsupported, so a program and the bindings compile on any platform and say plainly where no line opens.

Examples

use pamoja_gpio::linux;
use pamoja_gpio::pin::Level;
use pamoja_gpio::switch::{Contact, Switch};

// A relay board on GPIO17 that energizes on a low input, opened high so the pump stays
// off until it is asked to run, and a float switch to ground on GPIO27 with a pull-up.
let mut pump = Switch::active_low(linux::output("/dev/gpiochip0", 17, Level::High)?);
let mut float = Contact::active_low(linux::input("/dev/gpiochip0", 27)?);
pump.set(!float.is_asserted()?)?;

Structs

Line

A GPIO line opened on a Linux board, as an output or an input.

LineError

Why an open line could not be driven or read.

Enums

OpenError

Why a line could not be opened.

Constants

CONSUMER

The name the kernel shows as holding a line opened here, which gpioinfo prints.

Functions

input

Opens a line as an input.

output

Opens a line as an output, driving initial from the moment it is taken.