Low Latency Link (LoLa)

Software defined Link stack for Arduino HAL.

Goal for this project

Create a seamless bi-directional communication, real-time system, for Remote Control and Robotics applications (Example: RC car and remote).

Supported Platforms:

STM32F1
ESP32
RP2040
MegaAVR

Technical highlights

Synchonized clock between partners (+- 20us).
Fast encryption and MAC (~200us on ARM M3).
Collision avoidance with synchronized Duplex (period is configurable).
Optional full spectrum frequency hopping (period is configurable).
No low-level Tx retry mechanism.

Cryptography

Perfect forward secrecy (each session uses unique encoding).
32 bit MAC with integrity and authenticity validation.
MAC-then-Encrypt for fast rejection without decryption.
1-second rolling one-time-password combined with 16 bit counter, supports up 65535 packets/s before Nonce re-use.
No CRC needed on Transceiver.

Dependencies

TaskScheduler: https://github.com/arkhipenko/TaskScheduler
Memory efficient tracker: https://github.com/GitMoDu/BitTracker.git
Ascon128, Xoodyak and Poly1305: https://github.com/rweather/arduinolibs
Fletcher 16 CRC: https://github.com/RobTillaart/Fletcher
Driver for nRF24: https://github.com/nRF24/RF24
PSRNG: https://www.pcg-random.org
[EXPERIMENTAL]Micro Elyptic Curve Cryptography: https://github.com/kmackay/micro-ecc

LinkService

TemplateLinkService:

Exposes service to link-enabled actions (send packet, register receive port, etc..).
Provides asynchronous send packet. Tx occurs only when in slot and the transceiver is ready for Tx, with last moment OnPreSend call (for time sensitive payloads).
Priority levels for send (1-255).

AbstractDiscoveryService

Extends TemplateLinkService exposes service to actions after partner service is present, validated and synchronized

Implemented services

SyncSurface Service

Synchronises an array of N blocks (32bits wide) in a differential fashion, i.e., only send over radio the changing blocks, not the whole data array. There's a 2-way protocol to ensure data integrity without compromising data update latency.

Supported Transceivers

nRF24L01+ (depends on https://github.com/nRF24/RF24)
Si4463 (native driver and configurator)
UART (native driver)
VirtualTransceiver (for development and testing)
Esp32 ESPNow [WORK_IN_PROGRESS]
Sx12 LoRa [WORK_IN_PROGRESS]