RPPAL - Raspberry Pi Peripheral Access Library

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, 3B, 3B+, Compute, Compute 3, Zero and Zero W.

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

Documentation

Documentation for the latest release can be found at docs.golemparts.com/rppal. Documentation for earlier releases is stored at docs.rs/rppal.

Supported peripherals

GPIO

To ensure fast performance, RPPAL interfaces with the GPIO peripheral by directly accessing the registers through either /dev/gpiomem or /dev/mem. GPIO interrupts are controlled using the /dev/gpiochipN 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 configures 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 accesses 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

Usage

Add a dependency for rppal to your Cargo.toml.

[dependencies]
rppal = "0.8"

Link and import rppal from your crate root.

extern crate rppal;

Call Gpio::new() to create a new Gpio instance with the default settings. In production code, you'll want to parse the result rather than unwrap it.

use rppal::gpio::Gpio;

let mut gpio = Gpio::new().unwrap();

Example

extern crate rppal;

use std::thread;
use std::time::Duration;

use rppal::gpio::{Gpio, Mode, Level};
use rppal::system::DeviceInfo;

// The GPIO module uses BCM pin numbering. BCM GPIO 18 is tied to physical pin 12.
const GPIO_LED: u8 = 18;

fn main() {
    let device_info = DeviceInfo::new().unwrap();
    println!("Model: {} (SoC: {})", device_info.model(), device_info.soc());

    let mut gpio = Gpio::new().unwrap();
    gpio.set_mode(GPIO_LED, Mode::Output);

    // Blink an LED attached to the pin on and off
    gpio.write(GPIO_LED, Level::High);
    thread::sleep(Duration::from_millis(500));
    gpio.write(GPIO_LED, Level::Low);
}

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) 2017-2018 Rene van der Meer. Released under the MIT license.