Document how to update the axidraw EBB firmware

[osresearch]

These are my notes from how I did it for future incorporation into the readme.

Build mphidflash

sudo apt install libusb-dev
git clone https://github.com/EmbeddedMan/mphidflash
cd mpihidflash
sed -i 's/ -m32//' Makefile  # pi0 gcc doesn't support -m32 option
sudo make install32

Reset the axidraw and install the firmware

wget https://github.com/evil-mad/EggBot/raw/refs/heads/master/EBB_firmware/Releases/app/EBF_v303.zip
unzip EBF_v303.zip
sudo systemctl stop saxi
printf 'BL\r' > /dev/ttyACM0
sudo mphidflash -w EBF_v303/EBF_v303.hex -r