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]