rppal 0.10.0

Interface for the Raspberry Pi's GPIO, I2C, PWM and SPI peripherals.
Documentation

RPPAL - Raspberry Pi Peripheral Access Library

Build Status crates.io MIT licensed Minimum rustc version

RPPAL is a Rust library that provides access to the Raspberry Pi's GPIO, I2C, PWM and SPI peripherals. Support for additional peripherals will be added in future updates. The library is compatible with the Raspberry Pi A, A+, B, B+, 2B, 3A+, 3B, 3B+, Compute, Compute 3, Zero and Zero W.

Backwards compatibility for minor revisions isn't guaranteed until the library reaches v1.0.0.

RPPAL is currently under active development on the master branch of the repository on GitHub. If you're looking for the README.md or the examples folder for the latest release or any of the earlier releases, visit crates.io, download an archived release from the GitHub releases page, or clone and checkout the relevant release tag.

Documentation

Online documentation is available for the latest release, older releases, and the version currently in development.

Usage

Add a dependency for rppal to your Cargo.toml.

[dependencies]
rppal = "0.10"

Call new() on any of the peripherals to construct a new instance.

use rppal::gpio::Gpio;
use rppal::i2c::I2c;
use rppal::pwm::{Channel, Pwm};
use rppal::spi::{Bus, Mode, SlaveSelect, Spi};

let gpio = Gpio::new()?;
let i2c = I2c::new()?;
let pwm = Pwm::new(Channel::Pwm0)?;
let spi = Spi::new(Bus::Spi0, SlaveSelect::Ss0, 16_000_000, Mode::Mode0)?;

Some peripherals may need to be enabled first through sudo raspi-config or by editing /boot/config.txt. Refer to the relevant module's documentation for any required steps.

Examples

This example demonstrates how to blink an LED connected to a GPIO pin. Remember to add a resistor of an appropriate value in series, to prevent exceeding the maximum current rating of the GPIO pin and the LED.

use std::error::Error;
use std::thread;
use std::time::Duration;

use rppal::gpio::Gpio;
use rppal::system::DeviceInfo;

// Gpio uses BCM pin numbering. BCM GPIO 23 is tied to physical pin 16.
const GPIO_LED: u8 = 23;

fn main() -> Result<(), Box<dyn Error>> {
    println!("Blinking an LED on a {}.", DeviceInfo::new()?.model());

    let mut pin = Gpio::new()?.get(GPIO_LED)?.into_output();

    // Blink the LED by setting the pin's logic level high for 500ms.
    pin.set_high();
    thread::sleep(Duration::from_millis(500));
    pin.set_low();

    Ok(())
}

Additional examples can be found in the examples directory.

Supported peripherals

GPIO

To ensure fast performance, RPPAL controls the GPIO peripheral by directly accessing the registers through either /dev/gpiomem or /dev/mem. GPIO interrupts are configured using the gpiochip character device.

Features

  • Get/set pin modes
  • Read/write pin logic levels
  • Activate built-in pull-up/pull-down resistors
  • Configure synchronous and asynchronous interrupt handlers

I2C

The Broadcom Serial Controller (BSC) peripheral controls a proprietary bus compliant with the I2C bus/interface. RPPAL communicates with the BSC using the i2cdev device interface.

Features

  • Single master, 7-bit slave addresses, transfer rates up to 400kbit/s (Fast-mode)
  • I2C basic read/write, block read/write, combined write+read
  • SMBus protocols: Quick Command, Send/Receive Byte, Read/Write Byte/Word, Process Call, Block Write, PEC

PWM

RPPAL controls the Raspberry Pi's PWM peripheral through the /sys/class/pwm sysfs interface.

Features

  • Up to two hardware PWM channels
  • Configurable frequency/period, duty cycle and polarity

SPI

RPPAL controls the Raspberry Pi's main and auxiliary SPI peripherals through the spidev device interface.

Features

  • SPI master, mode 0-3, Slave Select active-low/active-high, 8 bits per word, configurable clock speed
  • Half-duplex reads, writes, and multi-segment transfers
  • Full-duplex transfers and multi-segment transfers
  • Customizable options for each segment in a multi-segment transfer (clock speed, delay, SS change)
  • Reverse bit order helper function

Caution

Always be careful when working with the Raspberry Pi's peripherals, especially if you attach any external components to the GPIO pins. Improper use can lead to permanent damage.

Cross compilation

If you're not working directly on a Raspberry Pi, you'll likely need to cross compile your code for the appropriate ARM architecture. Check out this guide for more information, or try the cross project for "zero setup" cross compilation.

Copyright and license

Copyright (c) 2017-2019 Rene van der Meer. Released under the MIT license.