CanBoot

Can Bootloader for STM32F103 MCUs

This bootloader is designed for CAN nodes to be used with Klipper. The bootloader itself makes use of Klipper's hardware abstraction layer, stripped down to keep the footprint minimal. Currently the bootloader reserves 8 KiB of space.

Building

CanBoot also uses Klipper's build system. The build is configured with menuconfig. The steps to fetch and build are as follows:

git clone https://github.com/Arksine/CanBoot
cd CanBoot
make menuconfig
make

The menuconfig will present the following options:

• Processor model: Currently STM32F042, STMF072, and STM32F103 models are supported.
• Disable SWD at startup: This is an option for GigaDevice STM32F103 clones. Note that these untested on this bootloader. This option only present for "STM32F103" models,
• Clock Reference: Choose the appropriate setting for your board's crystal
• CAN pins: Allows the user to choose which pins are wired to CAN.
• Flash Page Size: The STM32F103 comes in multiple variants. The low/medium density models have a 1 KiB page size, others a 2KiB page size. Choose the appropriate selection for your model. This option only present for "STM32F103" models,
• CAN bus speed: Select the appropriate speed for your canbus.
• Enable Status Led: Enables the option to select a status LED gpio.
• Status LED GPIO Pin: The pin name for your LED. The Pin can be inverted if the LED is on when the pin is low. For example, the status LED Pin for a "blue pill" is !PC13.

Once configured and built flash with a programmer such as an ST-Link. If you don't have a programmer available, it should be possible to flash STM32F103 devices via UART and STM32F042/72 devices over DFU. ST's STM32CubeProgrammer software can facilitate all of these methods, however there are also other tools such as stm32flash (UART) and dfu-util (USB DFU).

NOTE: Prior to flashing CanBoot it is recommended to do a full chip erase. Doing so allows CanBoot to detect that no application is present and enter the bootloader. This is required if your board does no have a reset button.

Uploading a Program

1. Build Klipper with CAN support and with the "8KiB" bootloader setting enabled.

2. Enter the bootloader. This may be accomplished through "double tapping" the Reset button. The second reset should be within 1.5 seconds of the first. If the Status LED is set it will blink every second when the device has entered the bootloader. A future patch to Klipper should make it possible for flash_can.py to direct the device to enter the bootloader.

3. Run the flash script:

   cd ~/CanBoot
   python3 flash_can.py -i can0 -f ~/klipper/out/klipper.bin -u <uuid>
   

   Replace with the appropriate uuid for your can device. If the device has not been previouisly flashed with Klipper, it is possible to query the bootloader for the UUID:

   flash_can.py -i can0 -q
   

FlashCan usage

Running flash_can.py -h to display help:

usage: flash_can.py [-h] [-i <can interface>] [-f <klipper.bin>] [-u <uuid>]
                    [-q]

Can Bootloader Flash Utility

optional arguments:
  -h, --help            show this help message and exit
  -i <can interface>, --interface <can interface>
                        Can Interface
  -f <klipper.bin>, --firmware <klipper.bin>
                        Path to Klipper firmware file
  -u <uuid>, --uuid <uuid>
                        Can device uuid
  -q, --query           Query Bootloader Device IDs

The interface option defaults to can0 if omitted. The firmware option defaults to ~/klipper/out/klipper.bin. The uuid must be specified unless the user is running a query with -q.

Notes

• It is recommended to USB CAN device flashed with candlelight, such as a Canable.
• If using a MCP2515 CAN Device (ie: Waveshare RS485 CAN HAT) it is possible that packets will be dropped when reading flash back from the node during the verification process. That said, I have successfully tested the 12 MHz Crystal variant with the recommended settings.
• If you have a STM32F103 device and the verification fails it is likely that you selected the wrong Flash Page Size.