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StackmatLink

🌐 English | 简体中文

StackmatLink is an open-source project based on the ESP32-S3. It captures the analog Stackmat signals from a GAN Halo (and other standard timers) audio port and converts them in real-time into the GAN Smart Timer Bluetooth Protocol.

With this project, you can bridge any standard non-Bluetooth Stackmat timer to csTimer wirelessly, eliminating the need for expensive Bluetooth-native hardware.

🌟 Key Features

  • Protocol Conversion: Seamlessly converts Stackmat Gen4 (1200 Baud) signals into the official GAN Bluetooth protocol (including the 0xFE magic packet and CRC16/CCIT-FALSE checksums).
  • Intelligent State Inference: Specifically handles the GAN Halo 'I' (Idle) state. It dynamically determines Running and Stopped states based on the time axis to ensure compatibility with csTimer.
  • Dual-Core Concurrency:
    • Core 1: Dedicated to high-precision signal sampling and parsing at 1200 Baud.
    • Core 0: Handles the NimBLE Bluetooth stack and Notify updates for zero-latency data transmission.
  • Automatic Phase Correction: Built-in logic to detect inverted signals (common in different LM393 wiring) and correct them on the fly.
  • Enhanced Visibility: Optimized BLE advertising parameters for instant discovery on Mac/PC Chrome and iPad/iOS.
  • Robust Connectivity: Implements a connection polling mechanism (getConnectedCount) to ensure stable data sync even when Bluetooth callbacks are delayed.

🛠 Hardware Requirements

  • MCU: ESP32-S3 (Tested on N16R8, but compatible with all S3 variants).
  • Signal Conditioning: LM393 Voltage Comparator Module.
  • Interface: 3.5mm Audio Jack (Tip: Signal, Sleeve: GND).
  • Electronic Components:
    • 1x 10kΩ Pull-up Resistor.
    • 2x 10kΩ Voltage Divider Resistors (to create a ~1.65V reference).

🔌 Wiring Diagram

Component ESP32-S3 Pin Description
LM393 VCC 3.3V Power Supply
LM393 GND GND Common Ground
LM393 Output GPIO 4 Requires 10kΩ Pull-up to 3.3V
3.5mm Tip LM393 IN+ Raw Timer Signal
Reference GND LM393 IN- 1.65V Ref (via Voltage Divider)

Signal Shaping Logic

Since the timer outputs a weak analog audio signal (sine-ish wave) with noise:

  1. Analog Stage: The signal (~0.7V–2.5V) enters the LM393 IN+.
  2. Comparison: The LM393 compares it against the fixed IN- (1.65V).
  3. Digital Stage:
    • Signal > 1.65V -> Output 3.3V.
    • Signal < 1.65V -> Output 0V.
  4. Result: A clean digital square wave is generated for the ESP32 UART to parse.

🚀 Installation

  1. Install Arduino IDE.
  2. Install the esp32 (by Espressif) board package.
  3. Install the NimBLE-Arduino library via the Library Manager.
  4. Open stackmattoble.ino and select your ESP32-S3 board.
  5. Note: If USB CDC On Boot is enabled, use the Native USB port for serial debugging.
  6. Click Upload.

📱 How to Use

  1. Power Up: Connect the ESP32-S3 to power and plug the audio cable into the timer.
  2. Verify Signal: Open Serial Monitor (115200 baud). Operate the timer; you should see Time: X:XX.XXX -> GAN: X.
  3. Connect to csTimer:
    • Go to csTimer.net (Chrome/Edge recommended).
    • Settings -> Timer -> Entering Type -> Bluetooth Timer.
    • Click the Bluetooth icon at the top of csTimer and pair with "GAN-Timer".
  4. Go!: Your physical timer is now synced with the digital solve.

⚠️ Troubleshooting

  • No Data: If the Serial Monitor shows GPIO 4 Level changing but no time is parsed, try setting the invert parameter to true in Serial1.begin.
  • LM393 Adjustment: Use a screwdriver to fine-tune the blue potentiometer on the LM393 until the signal triggers consistently.
  • Connectivity: Use Chrome (Windows/macOS/Android) or Bluefy (iOS) for the best Web Bluetooth experience.

📜 License

MIT License. Contributions and PRs are welcome!

Acknowledgments

This project was conceptualized by me and implemented in 2 hours with the help of AI pair programming. 本项目由我构思，并在 AI 结对编程的辅助下耗时两小时实现。