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

Packet Name	Packet Address	Status
Broadcast Frames
GPS	0x02	🟢
GPS Time	0x03	🟢
GPS Extended	0x06	🟢
Variometer Sensor	0x07	🟢
Battery Sensor	0x08	🟢
Barometric Altitude & Vertical Speed	0x09	🟢
Airspeed	0x0A	🟢
Heartbeat	0x0B	🟢
RPM	0x0C	🟢
TEMP	0x0D	🟢
Voltages	0x0E	🟢
Discontinued	0x0F	🟢
VTX Telemetry	0x10	🟢
Link Statistics	0x14	🟢
RC Channels Packed Payload	0x16	🟢
Subset RC Channels Packed	0x17	🔴
RC Channels Packed 11-bits	0x18	🔴
Link Statistics RX	0x1C	🟢
Link Statistics TX	0x1D	🟢
Attitude	0x1E	🟢
MAVLink FC	0x1F	🟢
Flight Mode	0x21	🟢
ESP_NOW Messages	0x22	🟢
Extended Frames
Parameter Ping Devices	0x28	🟢
Parameter Device Information	0x29	🟢
Parameter Settings (Entry)	0x2B	🔴
Parameter Settings (Read)	0x2C	🔴
Parameter Value (Write)	0x2D	🔴
Direct Commands	0x32	🟢
Logging	0x34	🟢
Remote Related Frames	0x3A	🟢
Game	0x3C	🟢
KISSFC Reserved	0x78 - 0x79	🔴
MSP Request	0x7A	🔴
MSP Response	0x7B	🔴
ArduPilot Legacy Reserved	0x7F	🔴
ArduPilot Reserved Passthrough Frame	0x80	🟢
mLRS Reserved	0x81, 0x82	🔴
CRSF MAVLink Envelope	0xAA	🟢
CRSF MAVLink System Status Sensor	0xAC	🟢

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