STM32 CAN Bootloader Programmer

A Python-based GUI tool to program STM32 microcontrollers over CAN bus, using the STM32 bootloader and the CAN protocol described in AN3154.

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How It Works

STM32 microcontrollers include a factory-programmed system memory bootloader that supports several communication interfaces — including CAN. When the MCU enters bootloader mode (either via the BOOT0 pin or by a software-triggered jump from the application), it listens for commands over CAN at 125 kbps.

This tool automates the full programming flow:

1. Jump trigger — Sends a configurable CAN frame to the running application to request a jump to the system bootloader (e.g. CAN ID 0x0DC, data 0x01).
2. Reconnect at 125 kbps — Closes the SLCAN interface and reopens it at the bootloader's fixed bitrate.
3. Sync — Exchanges the synchronisation frame (CAN ID = 0x079, data 0x00) until the bootloader acknowledges.
4. Get ID — Reads the MCU product ID (CMD_GET_ID, CAN ID = 0x02) for sanity checking.
5. Global Erase — Sends the erase command (CMD_ERASE, CAN ID = 0x43, data 0xFF).
6. Write — Programs the binary image in 256-byte chunks using CMD_WRITE (CAN ID = 0x31) followed by data frames (CAN ID = 0x04), with ACK/NACK checking after every frame.
7. Go — Sends the jump-to-application command (CMD_GO, CAN ID = 0x21) pointing to the flash base address (0x08000000).

The tool communicates with the CAN bus via an SLCAN-compatible USB adapter (CANable, Lawicel, etc.).

Protocol Reference

All CAN bootloader commands follow AN3154 (CAN protocol used in the STM32 bootloader). The system memory bootloader entry points for each MCU family are documented in AN2606 (STM32 microcontroller system memory boot mode).

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Requirements

pip install pyqt5 python-can pyserial cantools

Package	Purpose
pyqt5	GUI framework
python-can	CAN bus abstraction (SLCAN backend)
pyserial	Serial port enumeration for SLCAN adapters
cantools	DBC file parsing and CAN message encoding/decoding

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Usage

python CAN_STM32_Programmer.py

GUI Fields

Field	Description
COM Port	Serial port of your SLCAN adapter (e.g. COM7, /dev/ttyUSB0). Click Refresh to detect.
CAN ID (Hex)	ID of the CAN frame sent to trigger the bootloader jump in your application. Default: 0x0DC.
Data (Hex, space-separated)	Payload of the jump trigger frame. Default: 01.
Bitrate (normal CAN)	Bitrate of your application CAN bus (1 Mbit/s, 500k, 250k, 125k). The tool automatically switches to 125 kbps for the bootloader phase.
Firmware file	Path to the .bin file to flash.

Press Iniciar Programação do STM32 to start. The log console shows every step in real time.

Note: If the jump trigger ID/data fields are left as configured, they will match the defaults used in the provided STM32F412 example project (CAN ID = 0x0DC, data[0] bit 0 = 1).

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Repository Structure

.
├── CAN_STM32_Programmer.py      # Main application — GUI CAN flasher
├── README.md
├── examples/
│   └── f412_example_jump_to_bootloader/   # STM32F412 example (STM32CubeIDE project)
│       ├── Core/
│       │   ├── Src/
│       │   │   ├── main.c
│       │   │   └── bootloader_jumper.c    # CAN RX handler + JumpToBootloader()
│       │   └── Inc/
│       │       └── main.h
│       ├── STM32F412RETX_FLASH.ld
│       ├── STM32F412RETX_RAM.ld
│       └── f412_example_jump_to_bootloader.ioc
├── wiki/
│   ├── CAN_Setup_STM32F412.md             # CAN peripheral setup guide for STM32F412
│   └── CAN_Setup_STM32F103CBT6.md         # CAN peripheral setup guide for STM32F103CBT6
└── support/
    ├── AN3154_CAN_bootloader_protocol.md   # Summary + link — CAN bootloader protocol
    ├── AN2606_system_memory_boot_mode.md   # Summary + link — Bootloader entry per MCU family
    └── gonzabrusco_jump_to_bootloader.md   # Jump-to-bootloader guide (via gonzabrusco gist)

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STM32F412 Example Project

See examples/f412_example_jump_to_bootloader/.

This is a minimal STM32CubeIDE project for the STM32F412RETx that:

• Initialises CAN1 and CAN2 in HAL
• Configures a CAN2 receive filter (FIFO1, filter bank 14, pass-all mask) via CAN_Setup_Bootloader_Jumper()
• In the FIFO1 RX callback, checks for CAN ID = 0x0DC with data[0] & 0x01 == 1 and sets a flag
• In the main loop, checks the flag and calls JumpToBootloader() from Thread Mode

CAN2 configuration (250 kbps @ 32 MHz APB1):

Parameter	Value
Prescaler	16
TimeSeg1	2 TQ
TimeSeg2	5 TQ
SJW	1 TQ
Resulting bitrate	250 kbps

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Wiki

Step-by-step CAN peripheral setup guides:

• STM32F412 CAN Setup — Dual CAN, filter banks, FIFO assignment, SLCAN adapter wiring
• STM32F103CBT6 CAN Setup — Single CAN, pin remapping, bootloader address differences

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Support / References

• AN3154 — CAN protocol used in the STM32 bootloader
• AN2606 — STM32 microcontroller system memory boot mode
• How to Jump to the STM32 Bootloader and Return to the Application (gonzabrusco)

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Hardware Setup

  STM32 Board          SLCAN Adapter       PC
  ┌──────────┐        ┌────────────┐      ┌──────┐
  │ CAN2_TX  ├──┐  ┌──┤ CAN H      │      │      │
  │ (PB13)   │  └──┘  │            ├──────┤ USB  │
  │ CAN2_RX  ├──┐  ┌──┤ CAN L      │      │      │
  │ (PB5)    │  └──┘  │            │      └──────┘
  └──────────┘        └────────────┘
               

Replace PB5/PB13 with your actual CAN RX/TX pins. Add a 120 Ω termination resistor at each end of the CAN bus if your adapter does not include one.

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