flashtool does not check size prior to flashing?

[louisrousseau]

I have two STM32F042 devices I want to update regularly using Katapult over USB - a Klipper Expander and a "T. Abraham V0-Display" LCD board.

I've been dealing with the Expander for now, and I have encountered a few challenges due to that MCU's paltry 32k of storage.

• I had the flash tool hang and the status LED stop flashing on the Expander, until I realized that my Klipper build plus the 8k offset exceeded 32 kb. Back under that limit it flashes fine. (Did not notice Klipper's own make error about this, TODO - double check and open an issue there as well.)
• The current version of the code, with double reset click and the status LED enable yields a 4784 byte katapult.bin so I have to use an 8kb offset. Take out both and you get down to 4500, ways away from 4096. Would smaller increments be possible (say, 6 kb) or are there alignment constraints at play?
• Had to use Klipper's python3 -c 'import flash_usb as u; u.enter_bootloader("<DEVICE>")' to get the Expander to play nicely with flashtool.py, directly using the /dev/serial/by-id Klipper path as on my other CAN bus machine did not work, it timed out on command CONNECT.