std/gpio — Digital I/O pins

import std/gpio

The GPIO module provides digital pin control, organised per port. Every operation exists once for each port letter the architecture defines, with the port letter as the function suffix.

Ports

The module defines functions for ports a, b, c, d, e, f, g, h, j, k, l, m, q, and r — the full set of AVR port letters across the device family. Only the ports that physically exist on your selected target are usable; calling into a port the device does not have is not meaningful. The examples below use the _b port functions, since PB5 is a common on-board LED pin.

Each port X exposes the same four operations. They are documented once for port b; substitute the letter for any other port.

Operations

@pin_mode_b($pin: u8, $mode: u8)

Configure the direction of pin $pin (0–7) on the port. $mode is 1 for output and 0 for input — this drives the port’s Data Direction Register bit for that pin.

@digital_write_b($pin: u8, $val: u8)

Drive pin $pin (0–7) to $val: 1 sets the pin high, 0 sets it low. On a pin configured as input, writing 1 enables the internal pull-up, per the AVR port model.

@digital_read_b($pin: u8) -> u8

Read pin $pin (0–7) and return 1 if it is high or 0 if it is low.

@toggle_b($pin: u8)

Flip the output state of pin $pin (0–7).

Other ports

The identical set exists for every port letter:

• @pin_mode_a / @digital_write_a / @digital_read_a / @toggle_a

• @pin_mode_c / @digital_write_c / @digital_read_c / @toggle_c

• @pin_mode_d / @digital_write_d / @digital_read_d / @toggle_d

• … and so on for ports e, f, g, h, j, k, l, m, q, r.

Example

target atmega328p
import std/gpio

@main {
    @pin_mode_b(5, 1)              # PB5 as output (mode 1 = output)
    @pin_mode_b(0, 0)              # PB0 as input  (mode 0 = input)...
    @digital_write_b(0, 1)         # ...writing 1 to an input enables its pull-up

    loop * {
        ? @digital_read_b(0) == 0 {   # button pulls the pin low when pressed
            @toggle_b(5)              # flip the LED each time we read it low
        }
    }
}