ask433

A portable, no_std Amplitude Shift Keying (ASK/OOK) modem driver for 433 MHz RF transceivers.

This crate implements a full software modem compatible with cheap 433 MHz ASK/OOK transceivers (like FS1000A and XY-MK-5V), designed for use on both AVR (e.g. Arduino Uno) and ARM Cortex-M microcontrollers.

Features

• 🛠 Built with [embedded-hal] traits for maximum portability
• 📡 Software-based ASK modem with transmit & receive support
• 🧠 Demodulation via a software phase-locked loop (PLL)
• 🧾 RadioHead-compatible 4b6b symbol encoding
• 📦 Message framing with headers, preamble, and CRC validation
• 💤 Sleep, idle, transmit, receive, and CAD modes via AskMode
• 💥 Interrupt-safe using critical-section
• 🔒 no_std and embedded-friendly

How It Works

Each AskDriver instance manages the RF link using a timer-driven tick() interface. The driver samples the RX pin and modulates the TX pin at a fixed interval (usually every 62.5 µs for 2 kbps). All state — including framing, CRC, and symbol decoding — is handled in software.

use ask433::driver::AskDriver;
use embedded_hal::blocking::delay::DelayUs;
use heapless::Vec;

let mut driver = AskDriver::new(tx, rx, None, 8, None, None); // 8 ticks per bit (2kbps)
let mut delay = ...; // Your DelayUs provider

let msg = Vec::from_slice("Hello, World!".as_bytes()).unwrap();
driver.send(msg);

loop {
    driver.tick();
    delay.delay_us(63).ok();
    if driver.available() {
        if let Some(payload) = driver.receive() {
            // Handle message payload
        }
    }
}

Platform Support

You can use either: • delay-loop: a blocking loop to call tick() • timer-isr: an interrupt handler that calls tick()

See src/timer.rs for examples.

Buffer Sizes and Limits

• ASK_MAX_PAYLOAD_LEN: 67 bytes total (RadioHead compatible)
• ASK_HEADER_LEN: 4 bytes (to, from, id, flags)
• ASK_PREAMBLE_LEN: 8 bytes (0x55 training pattern)
• ASK_MAX_MESSAGE_LEN: 60 bytes usable application data
• ASK_MAX_BUF_LEN: Total transmission buffer (preamble + encoded)

Safety & Performance

• Fully interrupt-safe using critical-section
• No heap allocation or dynamic dispatch
• Efficient symbol encoding using lookup tables
• Overflow-safe millis()-based timers for duration tracking

License

Licensed under either of: • MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT) • Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

Contributing

Pull requests and issue reports are welcome! This project is in early development and feedback is appreciated — especially around portability, signal reliability, and architecture improvements.

Acknowledgements

• Inspired by RadioHead and VirtualWire • Uses 4b6b encoding patterns compatible with FS1000A-style radios • Built with <3 for embedded systems and open hardware