to update the MMDVM f446 firmware you need some special tricky commands:
after download the precompiled software from https://zumradio.com/downloads.html#precompiled
you need to add a special command for delays before flashing the firmware:
./stm32flash -R -i ‚,,,,,:rts&-dtr,,,2‘ /dev/AMA0
with reference to https://sourceforge.net/p/stm32flash/wiki/Home/
vy73 pse req if any questions to dk6px at amsat org