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 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

Type	Purpose	Memory
`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

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:

use peat_lite::{MessageType, Header, encode_header, NodeCapabilities};

Features

std (default): Standard library support
Disable for no_std: --no-default-features

# Cargo.toml - embedded usage
[dependencies]
peat-lite = { version = "0.2", default-features = false }

Building

# 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 (requires nightly):

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:

SSID="your-ssid" PWD="your-password" cargo +esp build --release \
  --features m5stack-core2-wifi --target xtensa-esp32-none-elf --bin peat-lite-wifi

peat-lite 0.2.5