Decrypting and reverse engineering proprietary Advanced Fire Alarm Polling Protocols.

An open-source initiative dedicated to researching, developing, and reverse-engineering the communication protocols of addressable fire alarm systems. This project aims to create some of the world's fastest and most robust polling algorithms for life-safety applications.

Commercial addressable fire alarm systems rely on sophisticated, proprietary protocols to communicate with hundreds of sensors over a single two-wire loop. This repository documents the journey of decrypting these methods and engineering new, high-performance open-source alternatives.

We explore both classic and modern techniques, from software-defined FSK (Frequency-Shift Keying) to the robust current/voltage modulation methods used in professional-grade systems. The goal is to push the boundaries of speed and reliability for microcontroller-based polling networks.

• Software-Defined FSK: Complete implementation of an FSK transmitter and receiver using the Goertzel algorithm on ESP32, including protocol-level robustness features.
• Current & Voltage Modulation: Design and implementation of a production-level communication scheme based on industry standards, using voltage dips for panel-to-sensor commands and current pulses for sensor-to-panel responses.
• Hardware Abstraction: Development of coupling and decoupling circuits to enable reliable communication over a 12V DC power line.
• Microcontroller Analysis: Comparative analysis of different MCU architectures for this task, including:
  • ESP32: For rapid prototyping and its powerful dual-core architecture.
  • ATtiny85 / PIC16F: Analyzing their role as ultra-low-power, cost-effective sensor nodes.
  • STM32 (G4/H7): Research into high-performance ARM cores with FPU/DSP for achieving maximum polling speeds.
• Protocol Optimization: A deep dive into stability and speed, implementing features like DC bias calibration, preambles, and various timing delays to create a near-flawless communication link.

This project utilizes a combination of hardware and embedded software to achieve its goals.

• Hardware Platforms:
  • ESP32 Dev Boards
  • Arduino Nano / ATtiny85
  • Custom Analog Front-End (Op-Amps, MOSFETs, Filters)
• Software & Algorithms:
  • C++ (Arduino Framework)
  • Goertzel Algorithm for FSK Demodulation
  • Custom Pulse-Width & Current-Pulse Protocols

• Develop and stabilize a software-defined FSK polling system. (Deprecated)
• Design and build a robust current/voltage modulation system.
• Design a custom PCB for the Panel and Sensor nodes.
• Implement a fully non-blocking, interrupt-driven state machine for maximum efficiency.
• Test the system with a large number of physical sensor nodes (100+).
• Implement a more advanced data protocol with CRC error checking.

Distributed under the MIT License. See LICENSE.txt for more information.

This project represents a deep exploration of embedded systems communication. Special thanks to all the resources and communities that make this research possible.