171 lines
5.6 KiB
Plaintext
171 lines
5.6 KiB
Plaintext
# STM8 Bootloader Template Project
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## Overview
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This project provides a flexible bootloader implementation for STM8 microcontrollers using the SDCC compiler. The bootloader resides in the option bytes reserved area and enables in-application programming (IAP) capabilities via UART communication.
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Note: The bootloader implementation is based on and inspired by the [STM8uLoader](https://github.com/ovsp/STM8uLoader) project, with significant modifications and enhancements for integration into this template structure.
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## Features
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- **Dual-stage Bootloader**:
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- Boot1: Minimal bootloader stored in option bytes (0x4812-0x483F)
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- Boot2: Full-featured bootloader loaded via serial communication
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- **Flexible Configuration**:
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- Enable/disable bootloader via `ENABLE_OPTION_BOOTLOADER` Makefile macro
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- Configurable communication parameters
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- **Complete Toolchain**:
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- PC-side programming utility for firmware updates
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- Support for read, write, verify, and reset operations
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- **Safe Operation**:
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- Bootloader integrity protected in option bytes
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- Fallback to application on timeout or communication failure
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## Bootloader Reference
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This project's bootloader implementation is derived from the excellent STM8uLoader project by ovsp. Key adaptations include:
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- Integration into a modular template project structure
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- Dual-stage bootloader approach (Boot1 in option bytes, Boot2 loaded dynamically)
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- Enhanced Makefile system with configuration macros
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- Extended command set and error handling
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## Bootloader Operation Flow
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1. **Power-on/Reset**:
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- MCU starts execution at reset vector
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- Control transfers to `bootloader_enter()` in `bsp/init0.c`
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2. **Stage 1 (Boot1)**:
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- Copies Boot1 from option bytes (0x4812-0x483F) to RAM and Run
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- Sends synchronization sequence `0x00 0x0D` via UART
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- Waits for PC to send Boot2 code
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3. **Stage 2 (Boot2)**:
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- Receives and validates Boot2 code from PC
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- Executes Boot2 which provides full command interface
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- Processes PC commands for programming, reading, and device control
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4. **Application Start**:
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- On successful programming or timeout, jumps to main application
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- Option to stay in bootloader mode for debugging
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## Building the Project
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### Prerequisites
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- SDCC (Small Device C Compiler) installed
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- stm8flash or similar programming tool
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- Python 3.x (for PC tools)
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### Compilation Options
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Enable bootloader support:
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```bash
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make ENABLE_OPTION_BOOTLOADER=1
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```
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Disable bootloader (direct application execution):
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```bash
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make ENABLE_OPTION_BOOTLOADER=0
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```
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### Build Targets
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```bash
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# Build both application and bootloader option
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make all
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# Program device (requires stm8flash)
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make flash
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```
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## Option Bytes Configuration
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The bootloader uses the reserved option byte area (0x4812-0x483F) for storage:
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| Address Range | Content | Size |
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|---------------|--------------------------|-------|
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| 0x4800-0x480A | Device option bytes | 11 bytes |
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| 0x4812-0x483F | Boot1 code | 46 bytes |
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**Important**: These addresses are specific to STM8S103/003. Adjust for other STM8 variants.
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## PC Communication Protocol
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### Connection Parameters
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- **Baud Rate**: 128000 bps
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- **Data Bits**: 8
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- **Parity**: None
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- **Stop Bits**: 1
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### Command Set
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| Command | Opcode | Description |
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|---------|--------|--------------------------------------|
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| READ | 0xF1 | Read memory from device |
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| WRITE | 0xF2 | Write memory to device |
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| ERASE | 0xF3 | Erase flash sectors |
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| RESET | 0xF4 | Reset to application |
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### Communication Sequence
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1. Boot1 sends sync bytes: `0x00 0x0D`
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2. PC responds with Boot2 code length
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3. Boot1 acknowledges and receives Boot2
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4. Boot2 executes and presents command prompt
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5. PC sends commands with appropriate parameters
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## Usage Example
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### Programming New Firmware
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```bash
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# 1. Build the application
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make ENABLE_OPTION_BOOTLOADER=1
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# 2. Connect to device
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python scripts/stm8isp.py --port /dev/ttyUSB0
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# 3. Follow interactive prompts to program
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# or use command line:
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python scripts/stm8isp.py --port /dev/ttyUSB0 --write firmware.ihx
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```
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## Supported Devices
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Currently tested with:
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- STM8S103/003 (default configuration)
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**Important**: To port to other STM8 variants need verify peripheral register definitions
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## Troubleshooting
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### Common Issues
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1. **No response from device**:
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- Verify baud rate settings
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- Check UART pin connections (TX/RX swapped?)
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- Ensure option bytes are correctly programmed
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2. **Bootloader not starting**:
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- Verify `ENABLE_OPTION_BOOTLOADER` is set during compilation
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- Check reset vector points to `bootloader_enter`
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- Confirm option bytes are protected from erasure
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## Safety Considerations
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1. **Power Stability**: Ensure stable power supply during programming
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2. **Watchdog Timer**: Disable or properly handle watchdog in bootloader
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3. **Interrupts**: Save/restore interrupt context during bootloader operations
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4. **Memory Protection**: Never overwrite bootloader area in option bytes
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## References
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- [STM8uLoader](https://github.com/ovsp/STM8uLoader)
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- [STM8S Reference Manual](https://www.st.com/resource/en/reference_manual/cd00190271-stm8s-series-and-stm8af-series-8bit-microcontrollers-stmicroelectronics.pdf)
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- [SDCC User Guide](http://sdcc.sourceforge.net/doc/sdccman.pdf)
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- [STM8 Bootloader AN2659](https://www.st.com/resource/en/application_note/cd00173937-stm8-swim-communication-protocol-and-debug-module-stmicroelectronics.pdf)
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---
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**Note**: This implementation is for educational and development purposes. Always verify bootloader behavior in your specific application context before deployment.
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