Getting to OTA DFU

[criegel]

We're trying to get to the point where we can update a FiPy's firmware over-the-air.

When would someone what to follow the instructions here:
https://github.com/pycom/pycom-micropython-sigfox#steps-for-using-secure-boot-and-flash-encryption
Specifically, am I correct in thinking the FiPy comes delivered with the bootloader already installed, and so the above is only necessary for newly manufactured hardware that has no bootloader on it? Or is the bootloader that ships with the FiPy not using Secure Boot/encryption and this process must be used to add these to protect the code from unintended eyes?

Going through the instructions linked to above, our pyTrack board shows up as ttyACM0 instead of ttyUSB0 (we tried both Ubuntu and Debian). Executing:

python $IDF_PATH/components/esptool_py/esptool/espefuse.py --port /dev/ttyACM0 burn_key flash_encryption flash_encryption_key.bin

we get

A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('\x08')

Thanks for any guidance you can offer!

[johand]

You have to go through all steps, the bootloader is not encrypted from the beginning.

I am not sure about the error. Did you boot into bootloader mode, if not, that might be your problem.