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, however it occupies less than 4 KiB.

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 STM32F203 is supported
• Clock Reference: Choose the appropriate setting for your board's crystal
• 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
• CAN bus speed: Select the appropriate speed for your setup
• Enable Status Led: If enabled, the option to set the Status LED Pin is made available
• 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. Make sure CanSerial is installed and enabled. Alternatively one can use the pycanserial.py script in this repo, however it requries Python 3.7+. It also lacks the "reset" feature of CanSerial, so for the moment I recommend using C version linked.
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. The bootloader should connect to CanSerial, and CanSerial should create a PTY for it in the /tmp directory.
3. Build Klipper with CAN support and with the "8KiB" bootloader setting enabled.
4. Run the flash script:

   cd ~/CanBoot
   ~/klippy-env/bin/python flash_can.py /tmp/ttyCANxxxxxxxx ~/klipper/out/klipper.bin
   

   Replace /tmp/CANxxxxxxxx with the appropriate symlink for your device.

Notes

• This is preview code and will almost certainly change. Specifically, it is anticipated that the flash_can script will not use CanSerial in the future, but instead connect directly to the CAN socket and issue commands to the bootloader. Likewise it is expected that it will be possible to enter the booltoader via command from Klipper. The IDs used to communicate with the bootloader may also change (0x321, 0x322, 0x323).
• 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.