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 only STM32F103 is 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 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.

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 <uuid>
   

   Replace with the appropriate uuid for your can device.

Notes

• If using a MCP2515 Can Device it is likely that packets will be dropped when reading flash back from the node during the verification process. Reducing SPI speed may help with this, in my testing the process could not complete at 10MHz. If possible use a USB can device flashed with candlelight.