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<img src="https://raw.githubusercontent.com/defenseunicorns/peat/main/assets/peat-wordmark.png" alt="PEAT" width="420">
</p>
# peat-lite
Brings the smallest devices into the Peat mesh — watches, microcontrollers, and sensors that have 256KB of RAM and no operating system. Part of the [Peat](https://github.com/defenseunicorns/peat) ecosystem.
## Overview
Not every device in a tactical network runs Linux. WearTAK runs on a Samsung watch. Sensors run on ESP32s. LoRa nodes have kilobytes of memory. These devices still need to participate in the mesh — sending status, receiving commands, syncing state.
peat-lite provides bounded, `no_std`-compatible CRDT primitives and a wire protocol that fits in 256KB of RAM:
## Primitives
| `NodeId` | 32-bit node identifier | 4 bytes |
| `CannedMessage` | Predefined message codes | 1 byte |
| `CannedMessageEvent` | Message with metadata | ~24 bytes |
| `CannedMessageStore` | LWW storage | ~6KB (256 entries) |
| `LwwRegister<T>` | Last-writer-wins register | sizeof(T) + 12 bytes |
| `GCounter` | Grow-only distributed counter | ~4 bytes per node |
## Usage
```rust
use peat_lite::{NodeId, CannedMessage, CannedMessageEvent};
let my_node = NodeId::new(0x12345678);
let event = CannedMessageEvent::new(
CannedMessage::Ack,
my_node,
Some(NodeId::new(0xDEADBEEF)), // target
1706234567000, // timestamp ms
);
// Encode for transmission (22 bytes)
let bytes = event.encode();
assert_eq!(bytes[0], 0xAF); // CannedMessage marker
```
## CannedMessage Codes
```
0x00-0x0F Acknowledgments ACK, WILCO, NEGATIVE, SAY AGAIN
0x10-0x1F Status CHECK IN, MOVING, HOLDING, ON STATION, RTB, COMPLETE
0x20-0x2F Alerts EMERGENCY, ALERT, ALL CLEAR, CONTACT, UNDER FIRE
0x30-0x3F Requests NEED EXTRACT, NEED SUPPORT, MEDIC, RESUPPLY
0xF0-0xFF Reserved Custom/application-specific
```
## Wire Protocol
The `protocol` submodule provides the canonical Peat-Lite binary wire protocol (ADR-035):
- 16-byte fixed header (magic, version, type, flags, node ID, seq num)
- Message types: Announce, Heartbeat, Data, Query, Ack, Leave, OTA (0x10-0x16)
- CRDT types: LwwRegister, GCounter, PnCounter, OrSet
- Node capability flags for Full/Lite negotiation
- TTL suffix support for data expiry
All protocol types are re-exported at the crate root for ergonomic access:
```rust
use peat_lite::{MessageType, Header, encode_header, NodeCapabilities};
```
## Features
- **`std`** (default): Standard library support
- Disable for `no_std`: `--no-default-features`
```toml
# Cargo.toml - embedded usage
[dependencies]
peat-lite = { version = "0.2", default-features = false }
```
## Building
```bash
# With std (default)
cargo build
# For embedded (no_std)
cargo build --no-default-features
# Run tests
cargo test
```
## Fuzzing
Fuzz targets cover all wire-format decode functions using [cargo-fuzz](https://github.com/rust-fuzz/cargo-fuzz) (requires nightly):
```bash
rustup toolchain install nightly
cargo +nightly fuzz list
cargo +nightly fuzz run fuzz_canned_message_event_decode
```
Targets:
- `fuzz_canned_message_event_decode` — `CannedMessageEvent::decode()` and `decode_auto()`
- `fuzz_canned_message_signed_decode` — `CannedMessageEvent::decode_signed()`
- `fuzz_canned_message_ack_decode` — `CannedMessageAckEvent::decode()`
- `fuzz_gcounter_decode` — `GCounter::decode()`
- `fuzz_decode_header` — `decode_header()`
Each target verifies encode/decode roundtrip consistency. Seed corpora are in `fuzz/corpus/`.
## License
Apache-2.0
## OTA Updates (ESP32)
peat-lite supports over-the-air firmware updates on ESP32 targets with A/B partitioning:
- Streaming SHA256 verification during transfer
- Ed25519 signature verification (optional, compile-time)
- Boot validation with automatic rollback (3 attempts)
- Stop-and-wait reliable transfer over UDP
Build with OTA support:
```bash
SSID="your-ssid" PWD="your-password" cargo +esp build --release \
--features m5stack-core2-wifi --target xtensa-esp32-none-elf --bin peat-lite-wifi
```