uf-crsf

A no_std Rust library for parsing the TBS Crossfire protocol, designed for embedded environments without an allocator.

This library provides a two-layer API:

• A low-level layer for raw packet parsing from a byte stream.
• A higher-level layer that converts raw packets into idiomatic Rust structs.

Features

• no_std and allocator-free for embedded systems.
• Two-layer API for flexible parsing.
• Supports a wide range of CRSF packets.
• IO and MCU agnostic.
• Minimal dependencies.

Implementation status

Legend:

• 🟢 - Implemented
• 🔴 - Not Implemented

Note

Library is under active development and testing, API might change at any time.

Installation

Add uf-crsf to your Cargo.toml:

[dependencies]
uf-crsf = "*" # replace * by the latest version of the crate.

Or use the command line:

cargo add uf-crsf

Usage

Here is a basic example of how to parse a CRSF packet from a byte array:

use uf_crsf::CrsfParser;

fn main() {
    let mut parser = CrsfParser::new();

    // A sample CRSF packet payload for RC channels
    let buf: [u8; 26] = [
        0xC8, // Address
        0x18, // Length
        0x16, // Type (RC Channels)
        0x03, 0x1F, 0x58, 0xC0, 0x07, 0x16, 0xB0, 0x80, 0x05, 0x2C, 0x60, 0x01, 0x0B, 0xF8, 0xC0,
        0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 252,  // Packet
        0x42, // Crc
    ];

    for item in parser.iter_packets(&buf) {
        match item {
            Ok(p) => println!("{:?}", p),
            Err(e) => eprintln!("Error parsing packet: {:?}", e),
        }
    }
}

Here is a basic example of how to parse and print telemetry CRSF packets from an ELRS TX16S radio controller, though it should work with any other EdgeTX device. Simply configure telemetry mirroring to a USB serial port and connect the controller to your PC.

use std::env;
use std::io::ErrorKind;
use std::process::exit;
use std::time::Duration;
use uf_crsf::CrsfParser;

fn main() {
    let ports = match serialport::available_ports() {
        Ok(ports) => ports,
        Err(e) => {
            eprintln!("Failed to enumerate serial ports: {}", e);
            exit(1);
        }
    };

    if ports.is_empty() {
        eprintln!("No serial ports found.");
        eprintln!("Please specify a serial port path as an argument.");
        exit(1);
    }

    let path = env::args().nth(1).unwrap_or_else(|| {
        const DEFAULT_PORT: &str = "/dev/tty.usbmodem00000000001B1";
        if ports.iter().any(|p| p.port_name == DEFAULT_PORT) {
            println!(
                "No serial port specified. Using default port: {}",
                DEFAULT_PORT
            );
            DEFAULT_PORT.to_string()
        } else {
            println!("No serial port specified. Available ports:");
            for p in &ports {
                println!("  {}", p.port_name);
            }
            println!("\nUsing first available port: {}", ports[0].port_name);
            ports[0].port_name.clone()
        }
    });

    let mut port = serialport::new(&path, 420_000)
        .timeout(Duration::from_millis(10))
        .open()
        .unwrap_or_else(|e| {
            eprintln!("Failed to open serial port '{}': {}", &path, e);
            exit(1);
        });

    let mut buf = [0; 1024];
    let mut parser = CrsfParser::new();
    println!("Reading from serial port '{}'...", path);
    loop {
        match port.read(buf.as_mut_slice()) {
            Ok(n) => {
                for packet in parser.iter_packets(&buf[..n]) {
                    println!("{:?}", packet);
                }
            }
            Err(ref e) if e.kind() == ErrorKind::TimedOut => {
                // This is expected when no data is coming in
            }
            Err(e) => {
                eprintln!("Error reading from serial port: {}", e);
                break;
            }
        }
    }
}

License

This project is licensed under the Apache 2.0. See the LICENSE file for details.

Protocol Specification

• Official TBS CRSF Protocol Specification
• CRSF Working Group Fork