Bootstrap pins on MicroMod connector can cause incompatibilities

[shulltronics]

Hi there,

I'm one of the SPE design challenge participants, so I received a Single Pair Ethernet kit that includes this board. When I started to play with this kit, I realized that I couldn't flash the Esp32! This was my first time working with one, so I subsequently learned about the bootstrap pins, and then realized that GPIO12 on the Esp32 (broken out to PWM1 (pin 47?) on the MircoMod connector) was being pulled high by the SPE function board. See sparkfun/SparkFun_MicroMod_Single_Pair_Ethernet_Function_Board_ADIN1110#1.

Work Around

I was able to burn the efuses on the Esp32 with espefuse.py set_flash_voltage 3.3V to hard-code the MCU's internal flash to 3.3V.

Possible Solutions

While the work around seems to allow the boards to work together, it doesn't seem like the ideal solution, as it requires some specialized knowledge to get to that solution, and is an irreversible action. The only way I could see this being feasible is if Sparkfun did the fuse setting before shipping these boards to customers. The most robust solution, though maybe too limiting, is to remove the bootstrap pins from the MicroMod connector entirely. This would prevent any incompatibilities with future function boards.

Anyway, I would love to hear your thoughts on this! :) Thanks!