edlora 1.2.2

A lightweight cross-language communication protocol for rocketry telemetry over LoRa.

edLoRa Protocol

A lightweight, cross-language (C++ & Python) binary protocol designed specifically for rocketry telemetry and command data over LoRa modules. Supports both standard Linux and ESP32 platforms in C++, and comes with a Python 3 ground station implementation.

Features

• Binary Packing: Completely avoids string processing to keep LoRa bandwidth usage minimal.
• Robust Framing: Dedicated sync bytes, payload length checking, and CCITT CRC-16 checksums ensure data integrity even on noisy RF channels.
• Multi-node addressing: Includes Sender ID and Receiver ID (with 0xFF reserved for Broadcast).
• Message Types: Differentiates traffic types (e.g., GPS, IMU, Altimeter, Commands).
• Embedded Friendly: The C++ implementation avoids dynamic memory allocation entirely, protecting against heap fragmentation on ESP32/Arduino.
• Optional Crypto: Includes a lightweight XOR-cipher wrapper inside edlora_crypto for obfuscating payload bytes. (Easily swappable with AES if actual cryptographic security is required).

Extensive Documentation

If you are planning to deploy edLoRa for a competition-grade architecture, please review the extensive documentation to fully understand the protocol specification and how to utilize it effectively:

• 📖 Protocol Architecture & Reasoning — Why the protocol relies on binary struct-packing, Sync Bytes, auto-injected timestamps, and how the MsgType::ACK (Command Acknowledgement) bouncing mathematically maps packet delivery.
• 🚀 Getting Started Guide — In-depth code implementation details for initializing, packing, and securely parsing valid buffers on both ESP32/Arduino and Python.
• 💻 CLI Stream Monitor — How to test your packet layout by streaming raw RF bytes directly from a serial LoRa module into a terminal window using the examples/cli_monitor.py GUI.

Directory Structure

• cpp/: C++ header (edlora.h) and source implementation for ESP32/Linux.
• python/: Python 3.x module (edlora.py) for the Ground Station / decoding logic.
• examples/: Sample usage scripts demonstrating perfect cross-language compatibility.
  • test_linux.cpp and test_python.py demonstrate basic raw packing/unpacking.

Message Types (MsgType)

To allow for structured data, edLoRa categorizes packets using the MsgType byte:

Name	Hex Value	Description
HEARTBEAT	0x00	Simple keep-alive or ping.
GPS	0x01	Latitude, Longitude, Fix Type, Sat count.
ALTIMETER	0x02	Altitude and velocity telemetry data.
IMU	0x03	Raw Accel, Gyro, Mag data.
COMMAND	0x04	Ground-to-vehicle commands or text logs.
SYS_STATE	0x05	System battery, temp, and current flight phase.
ORIENTATION	0x06	Calculated attitude (Quaternions/Euler angles).
EVENT	0x07	Major flight events (Liftoff, MECO, Apogee, Deployment).
ACK	0xFD	Command Acknowledgement (Payload = original seq_num).
ERROR_MSG	0xFE	Faults and system error states.
CUSTOM	0xFF	Freeform binary payloads.

Device Addressing & Broadcasting

Every packet encapsulates a Sender_ID and a Receiver_ID allowing you to strictly route telemetry between multiple rockets and ground stations.

• Set the Receiver_ID to 0xFF (which is mapped to Packet::BROADCAST_ID / Packet.BROADCAST_ID in Python) if you want all listening ground stations/nodes to process the packet.
• When un-packing, use the builtin boolean check rx.is_targeted_to(YOUR_ID) to safely filter out noise intended for other modules!

Usage Guide (C++)

Include edlora.h and edlora.cpp in your ESP-IDF or Arduino project.

#include "edlora.h"

using namespace edlora;

void loop() {
    Packet tx_packet;
    tx_packet.sender_id = 0x10;
    tx_packet.receiver_id = 0xFF; // Broadcast
    tx_packet.msg_type = MsgType::GPS;
    tx_packet.seq_num = 1;

    // Option 1: Send raw bytes
    // tx_packet.payload_len = 4;
    // tx_packet.payload[0] = 0xDE;
    // tx_packet.payload[1] = 0xAD;
    // tx_packet.payload[2] = 0xBE;
    // tx_packet.payload[3] = 0xEF;

    // Option 2: Send strings effortlessly
    tx_packet.set_payload_string("Rocket Stage 1 separated!");

    // Optional Crypto:
    // crypto::XorCipher cipher(0xAA);
    // cipher.process(tx_packet);

    // Pack for transmission
    uint8_t tx_buffer[256];
    int packed_size = Protocol::pack(tx_packet, tx_buffer, sizeof(tx_buffer));

    if (packed_size > 0) {
        // Send tx_buffer[0 ... packed_size-1] over your LoRa modem
        // LoRa.beginPacket();
        // LoRa.write(tx_buffer, packed_size);
        // LoRa.endPacket();
    }
}

// Example: Receiving & Acknowledging in C++
void receive_example(uint8_t* rx_buffer, size_t length) {
    Packet rx_packet;
    
    // Unpack incoming bytes
    if (Protocol::unpack(rx_buffer, length, rx_packet)) {
        if (rx_packet.is_targeted_to(0x10)) {
            // Use your received data!
            if (rx_packet.msg_type == MsgType::COMMAND) {
                // Execute command...
                
                // Construct an automated ACK payload and pack it
                Packet ack = rx_packet.create_ack(0x10, millis());
                
                uint8_t reply_buf[256];
                int reply_len = Protocol::pack(ack, reply_buf, sizeof(reply_buf));
                // LoRa.write(reply_buf, reply_len);
            }
        }
    }
}

Usage Guide (Python)

from edlora import Packet, MsgType
from edlora_crypto import XorCipher

# Assume `rx_bytes` is the raw byte array received from Ground Station LoRa
rx_bytes = b'\xed\x10\xff\x01\x01\x04\xde\xad\xbe\xef\x00\xb1'

try:
    packet = Packet.unpack(rx_bytes)
    
    # Optional Crypto decoding:
    # cipher = XorCipher(0xAA)
    # packet = cipher.process(packet)
    
    # Retrieve raw bytes
    print(f"Payload (Bytes): {packet.payload}")
    
    # Retrieve as a decoded string
    print(f"Payload (String): {packet.get_payload_string()}")
    
    # Check Timestamp
    print(f"Time (ms): {packet.timestamp}")
except ValueError as e:
    print(f"Packet corrupted or rejected: {e}")


# Example: Unpacking specific message types
import struct
from edlora import Packet

p = Packet.unpack(rx_bytes) # Automatically validates sync byte and CRC16

# Extract targeted or broadcast addressing
is_for_me = p.is_targeted_to(0x01) 

if p.msg_type == MsgType.ALTIMETER:
    alt, vel = struct.unpack("<ff", p.payload)
    print(f"Altimeter: {alt}m, {vel}m/s")
elif p.msg_type == MsgType.ACK:
    print(f"Received ACK for Sequence Number: {p.payload[0]}")

Serial Monitor (CLI)

You can directly stream incoming data out of a physical LoRa module connected via USB using the cli_monitor.py example script. It fully handles framing raw serial bytes into complete Packets.

pip install pyserial
python3 examples/cli_monitor.py --port /dev/ttyUSB0 --baud 115200

Outputs formatted logs: [15:30:22.123] [0x10] [ALTIMETER] [BROADCAST] Altitude: 1500.5m, Velocity: 20.3m/s

Example: Transmitting from Python

tx_packet = Packet(
    sender_id=0xFF,   # Ground station ID
    receiver_id=0x10, # Rocket ID
    msg_type=MsgType.COMMAND,
    seq_num=42,
    timestamp=12584   # Milliseconds
)

tx_packet.set_payload_string("DEPLOY PARACHUTE")
bytes_to_send = tx_packet.pack()

# Send `bytes_to_send` over your serial/USB LoRa module!
# serial_port.write(bytes_to_send)