lezyne-rear-light-firmware

🚧 Work in progress. No complete firmware yet 🚧

🚀 For pre-build binaries go to Releases.

Open firmware for Lezyne bike rear lights based on ATTINY202

This repository contains a minimal firmware as a C project for the ATtiny202 microcontroller using GCC, CMake, and VS Code. It also includes instructions for programming the chip using an FT232 USB-UART adapter via the UPDI interface with pymcuprog.

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Table of Contents

• Dependencies
• Setup Build Environment
• Building the Project
• Flashing the Firmware
• Reading Flash Content
• Hardware Setup
• License

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Dependencies

Ensure the following tools are installed on your system:

• GCC AVR toolchain (supports ATtiny 0/1-series)

  sudo zypper install avr-gcc avr-libc
  

• CMake

    sudo zypper install cmake
  

• Python 3, pip and venv

    sudo zypper install python3 python3-pip python3-venv
  

• VS Code (optional but recommended)
• CMake Tools extension for VS Code

Setup Build Environment

1. Clone the repository:

    git clone https://git.mosad.xyz/localhorst/lezyne-rear-light-firmware
    cd lezyne-rear-light-firmware
   

2. Configure the CMake project:
   • Open the folder in VS Code.
   • Select the AVR-GCC kit in the bottom blue bar.
   • Run CMake: Configure (from command palette) if it doesn't auto-run.

Building the Project

1. Press F7 or Ctrl+Shift+B to build.
2. Output files are generated in the 'build/' folder:

• main.elf → ELF executable
• main.hex → HEX file (flashable)
• main.bin → BIN file

Flashing the Firmware

Hardware: FT232 USB-UART adapter connected to UPDI with a 4.7 kΩ resistor.

1. Create and activate a Python virtual environment:

    python3 -m venv pyupdi-env
    source pyupdi-env/bin/activate
   

2. Install pymcuprog inside the environment:

    pip install pymcuprog
   

3. Verify installation:

    pymcuprog --version
   

4. Flash using pymcuprog:

    pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 write -f build/main.hex
   

Hardware Setup (FT232 → ATtiny202 UPDI)

 FT232 TX ----[4.7kΩ]---- UPDI (Pin 6)
 FT232 GND --------------- GND
 VCC -------------------- VCC (3.3V or 5V, must match FT232 logic)

Hint: The GPIO PA0 acts as UPDI of ATtiny202 and needs to be disconnected from the PCB during programming.

ATtiny202-SSN Pin Mapping (PCB Usage)

Pin #	Pin Name	Port	PCB Usage	Direction
1	VDD	—	+VDD (Power)	Power Input
2	PA6	IO	Green LED	Output
3	PA7	IO	Red LED	Output
4	PA1	IO	LED 1–2	Output
5	PA2	IO	LED 3–6	Output
6	PA3	IO	LED 7–8	Output
7	PA0	IO	UPDI / Activation Button	Input (button, pull-up) / UPDI (program)
8	GND	—	Ground	Power Ground

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Logic Levels (LEDs & Button)

Signal	PCB Usage	LOW	HIGH
PA6	Green LED	LED ON	LED OFF
PA7	Red LED	LED ON	LED OFF
PA1	LED 1–2	LED(s) OFF	LED(s) ON
PA2	LED 3–6	LED(s) OFF	LED(s) ON
PA3	LED 7–8	LED(s) OFF	LED(s) ON
PA0	Activation Button	Button pressed (GND)	Button released (pull-up)

License

This project is licensed under the MIT License. See LICENSE for details.