Espressif Rust

ESP-NOW in Rust

On ESP32 Microcontrollers

FEKT VUT Brno |

Why Rust on ESP32?

  • Memory Safety: No buffer overflows or dangling pointers. Essential for devices running 24/7.
  • Testability: Functional features (Iterators, Enums, Pattern Matching) allow you to separate logic from hardware.
    Result: Test logic on your PC, flash to MCU with confidence.
  • Espressif Ecosystem:
    Official support (esp-rs) and esp-hal v1.0.0 (Stable API) was recently released.

The Foundation: Embassy

This project relies heavily on Embassy — the Async Embedded Runtime.

  • Async/Await on Hardware: Write concurrent code like it's JavaScript or Go, but on bare metal.
  • No RTOS Required: No FreeRTOS complexity. The executor manages tasks cooperatively.
  • Efficiency: Handles Wi-Fi, Timers, and GPIO simultaneously with zero-cost abstractions.
// Embassy makes async easy #[embassy_executor::task] async fn connection_task(mut controller: WifiController) { loop { match controller.connect().await { Ok(_) => info!("Wifi connected!"), Err(e) => warn!("Failed to connect: {:?}", e), } Timer::after(Duration::from_secs(5)).await; } }

Why ESP-NOW for Automation?

Advantages

  • Instant Boot & Send (< 100ms)
  • Extremely Low Power
  • Long Range (Wi-Fi PHY)
  • No Router / IP stack overhead

Constraints

  • Small Payload (250 Bytes)
  • No Direct Internet Connection
  • Connectionless (Send & Pray/Ack)

Technology Comparison

Feature ESP-NOW Zigbee Wi-Fi Station Bluetooth LE
Topology Peer-to-Peer Mesh Star (Central) P2P / Mesh
Hardware Standard ESP32 Special Radio Standard ESP32 Standard ESP32
Range High (Hundreds m) Medium High Low
Battery Life Excellent Excellent Poor Good
Hub? Optional (DIY) Required Router Req. Phone/Gateway

The Hardware: C3 SuperMini

  • Chip: ESP32-C3 (RISC-V Architecture)
  • Design: Minimalist, cheap, widely available (AliExpress/JLCPCB)
  • Role: Perfect for battery powered sensors

Hardware Info: sidharthmohannair/Tutorial-ESP32-C3-Super-Mini
My Rust Examples: github.com/Hahihula/esp32-c3-super-mini-rust
(*Examples require update to esp-hal 1.0)

The Connectivity Gap

Smart devices on ESP-NOW are "invisible" to your PC.
They don't have IP addresses. They don't show up on your Router.

Solution: The USB Gateway

  • A dedicated ESP32-C3 plugged into USB.
  • Listens on ESP-NOW Channel 11.
  • Bridges packets to Serial Terminal (UART).

System Architecture

[ Temp Sensor ] ))) ESP-NOW ((( | [ Light Switch] ))) ESP-NOW ((( --> [ GATEWAY C3 ] | | [ Motion Det. ] ))) ESP-NOW ((( | USB / UART v [ Raspberry Pi / PC ] (Interactive Terminal)

Use the gateway for debugging or as a Home Assistant bridge.
repo: esp32-c3-supermini-esp-now-gateway

LIVE DEMO

Connecting to Gateway terminal...

Checking for broadcasts on Channel 11

Resources & Future


Note: The code presented works on any ESP32, but was validated on the C3 SuperMini.

Q & A

Thank you!

Espressif Rust