# RPPAL - Raspberry Pi Peripheral Access Library
[](https://travis-ci.org/golemparts/rppal)
[](https://crates.io/crates/rppal)
[](LICENSE)
[](https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html)
RPPAL provides access to the Raspberry Pi's GPIO, I2C, PWM and SPI peripherals through a user-friendly interface. In addition to peripheral access, communicating with USB serial devices is supported as well. The library can be used in conjunction with a variety of platform-agnostic drivers through its `embedded-hal` trait implementations by enabling the optional `hal` feature.
RPPAL requires Raspbian or any similar, recent, Linux distribution. Both `gnu` and `musl` libc targets are supported. RPPAL is compatible with the Raspberry Pi A, A+, B, B+, 2B, 3A+, 3B, 3B+, CM, CM 3, CM 3+, Zero and Zero W. Backwards compatibility for minor revisions isn't guaranteed until v1.0.0.
This library is under active development on the [master branch](https://github.com/golemparts/rppal/tree/master) of the repository on GitHub. If you're looking for the `README.md` or the `examples` directory for the latest release or any of the earlier releases, visit [crates.io](https://crates.io/crates/rppal), download an archived release from the GitHub [releases](https://github.com/golemparts/rppal/releases) page, or clone and checkout the relevant release tag.
## Table of contents
- [Documentation](#documentation)
- [Usage](#usage)
- [Examples](#examples)
- [Optional features](#optional-features)
- [Supported peripherals](#supported-peripherals)
- [GPIO](#gpio)
- [I2C](#i2c)
- [PWM](#pwm)
- [SPI](#spi)
- [Cross compilation](#cross-compilation)
- [Cargo](#cargo)
- [RLS](#rls)
- [Caution](#caution)
- [Copyright and license](#copyright-and-license)
## Documentation
Online documentation is available for the latest release, older releases, and the version currently in development.
* Latest release: [docs.golemparts.com/rppal](https://docs.golemparts.com/rppal)
* Older releases: [docs.rs/rppal](https://docs.rs/rppal)
* In development: [docs.golemparts.com/rppal-dev](https://docs.golemparts.com/rppal-dev)
## Usage
Add a dependency for `rppal` to your `Cargo.toml`.
```toml
[dependencies]
rppal = "0.11"
```
If your project requires `embedded-hal` trait implementations, specify the `hal` feature in the dependency declaration.
```toml
[dependencies]
rppal = { version = "0.11", features = ["hal"] }
```
Call `new()` on any of the peripherals to construct a new instance.
```rust
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)?;
```
Access to 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.
```rust
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 500 ms.
pin.set_high();
thread::sleep(Duration::from_millis(500));
pin.set_low();
Ok(())
}
```
Additional examples can be found in the `examples` directory.
## Optional features
By default, all optional features are disabled. You can enable a feature by specifying the relevant feature name(s) in the dependency declaration for the `rppal` crate.
* `hal` - Adds `embedded-hal` trait implementations for all supported peripherals. Doesn't include unproven traits.
## Supported peripherals
### [GPIO](https://docs.golemparts.com/rppal/latest/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
* Software-based PWM implementation
* Optional `embedded-hal` trait implementations (`OutputPin`, `PwmPin`)
### [I2C](https://docs.golemparts.com/rppal/latest/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 400 kbit/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
* Optional `embedded-hal` trait implementations (`Read`, `Write`, `WriteRead`)
### [PWM](https://docs.golemparts.com/rppal/latest/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, duty cycle and polarity
* Optional `embedded-hal` trait implementations (`PwmPin`)
### [SPI](https://docs.golemparts.com/rppal/latest/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
* Optional `embedded-hal` trait implementations (`FullDuplex `, `Transfer `, `Write `)
## Cross compilation
If you're not working directly on a Raspberry Pi, you'll have to cross-compile your code for the appropriate ARM architecture. Check out [this guide](https://github.com/japaric/rust-cross) for more information, or try the [cross](https://github.com/japaric/cross) project for "zero setup" cross compilation.
### Cargo
While additional steps may be necessary to cross-compile binaries on your platform, checking your code with `cargo check` only requires the installation of an appropriate target. Most Raspberry Pi models need the `armv7-unknown-linux-gnueabihf` target. For some models, like the Raspberry Pi Zero, a different target triple is required.
Install the relevant target using `rustup`.
```bash
rustup target install armv7-unknown-linux-gnueabihf
```
In the root directory of your project, create a `.cargo` subdirectory, and then save the following snippet to `.cargo/config`.
```toml
[build]
target = "armv7-unknown-linux-gnueabihf"
```
### RLS
RLS needs to be made aware of the target platform by setting the `rust.target` configuration option. The location of this option is IDE-specific.
#### Visual Studio Code
In the root directory of your project, create a `.vscode` subdirectory, and then save the following snippet to `.vscode/settings.json`.
```json
{
"rust.target": "armv7-unknown-linux-gnueabihf"
}
```
## 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.
## Copyright and license
Copyright (c) 2017-2019 Rene van der Meer. Released under the [MIT license](LICENSE).