Potential issue with GPIO12

[sebastius]

GPIO12 (MTDI pin) on the ESP32 when pulled high on boot sets another LDO voltage:

Which will cause a brownout on the flash-chip in the wrover. We've learned that the hard way with the Hackerhotel 2019 badge project i was part of.

No idea if the display is capable of pulling the pin high on boot, but it might be interesting to verify. I have a few V2 boards (with my modifications bodged in) that aren't booting right now, will look into this.

A fix is relatively easy: burning a fusebit will set the voltage permanently. It is however unfortunate that not all wrovers require the same voltage IIRC.

[vroland]

The more you know... Thanks for sharing! So far I did not encounter the issue with any of my displays, but when I've got access to as scope I can look for anything suspicious.

[vroland]

If I'm seeing it corrently, GPIO12 is not connected to any display pin. It is broken out as MISO, thus the internal pull-down should do its job...

[sebastius]

I think i misread the schematic then :) So it's a non-issue, might be useful to update the readme with a caveat.

[vroland]

Addressed in f4ac37a.