uf-sbus

A no_std compatible Rust library for parsing and encoding SBUS (Serial Bus) packets commonly used in RC systems. SBUS is a protocol developed by Futaba for RC receivers to communicate with flight controllers and other devices.

SBUS Protoc0l

The protocol runs on top of UART communication. Typical parameters are 100kbps (or 200kbps in fast mode), 8e2 frame format, inverted (high voltage level is logic low).

Byte[0]: SBUS header, 0x0F
Byte[1 -22]: 16 servo channels, 11 bits each
Byte[23]
    Bit 0: channel 17 (0x01)
    Bit 1: channel 18 (0x02)
    Bit 2: frame lost (0x04)
    Bit 3: failsafe activated (0x08)
Byte[24]: SBUS footer

Installation

cargo add uf-sbus

[dependencies]
uf-sbus = { version="0.1.0", features = ["defmt"] }

Simple example

use uf_sbus::SbusParser;

fn main() {
    println!("simple example ");
    let data: [u8; 25] = [
        0x0F, 0xE0, 0x03, 0x1F, 0x58, 0xC0, 0x07, 0x16, 0xB0, 0x80, 0x05, 0x2C, 0x60, 0x01, 0x0B,
        0xF8, 0xC0, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 00,
    ];
    let mut sbus = SbusParser::new();

    for result in sbus.iter_packets(&data) {
        match result {
            Ok(packet) => {
                println!("{:?}", packet)
            }
            Err(err) => {
                println!("Parsing failed with {:?}", err)
            }
        }
    }
}

Embassy

See esp32c6 example for complete code:

    let mut uart = uart0.into_async();
    let mut buf: [u8; 25] = [0; 25];
    let mut sbus = SbusParser::new();
    let timeout = 500;  // Default from betaflight

    loop {
        // Read with timeout using embassy_time features
        let result = with_timeout(Duration::from_millis(timeout), uart.read_async(&mut buf)).await;
        match result {
            Ok(Ok(size)) => {
                for result in sbus.iter_packets(&buf[..size]) {
                    match result {
                        Ok(packet) => info!("Sbus Packet: {:?}", packet.channels),
                        Err(e) => info!("Sbus Error: {:?}", e),
                    }
                }
            }
            Ok(Err(read_error)) => {
                info!("UART reading error {:?}", read_error)
            }
            // Timeout happened, internal buffer possibly contain partial packet,
           // good idea to reset parser and start waiting for header again.
            Err(TimeoutError) => sbus.reset(),
        }
    }
}

References

Protocol decoder from sigrok https://sigrok.org/wiki/Protocol_decoder:Sbus_futaba
Arduino library https://github.com/bolderflight/SBUS

License

Licensed under the Apache License, Version 2.0

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

uf-sbus 0.1.0