ESP32-S2 and USB on a custom pcb

[JorisKingma]

Hi everyone,

After many, many hours of designing I've finally got a bunch of custom esp32-S2 boards in. They look great, however there's a huge challenge: I can't get them to work! That is, when connecting the board to my laptop (Windows 10) the boards are not recognised.

1 or 2 faulty boards are highly unlikely; every board I connect does not seem to be doing anything.

After many hours of surfing to look for clues on the cause of this issue, I'm seeking your help.

There are a few things I've tested so far:
- The Crystal oscillator seems to be working alright. That also indicates that the ESP is properly powered on since it feeds the crystal with power to start oscillating.
- The PCB traces for USB (D- and D+) seem to be fine; resistance from start to end is practically 0.

Attached is an image of the KiCad design of the board. And for those interested a zip file with the KiCad design (board and schematic).
Please note that the ADC (MCP3421) an it's components are not populated.

Possibles causes are very welcome!
I'd love to hear from you thanks a million in advance!

Joris Kingma

[ESP_Sprite]

First of all, that LP5907 could be an issue; if not now, then later. I'm decently sure we advise a LDO capable of >=500mA for that chip; your LDO only does 250mA. Not sure if that affects USB, but it may very well cause weirdness when you enable WiFi.

Furthermore, do you pull down IO0 when trying to program the chip? The -S2 needs a working and well-configured program in flash to automatically get into download mode; if you don't have that you need to pull GPIO0 low.

[JorisKingma]

Thanks for your extensive reply! I'll exchange the LDO for a more beefy version.

I expected the S2 to just show on connect regardless of the IO0 state.
I did try resetting the chip while holding IO0 but that didn't solve the issue (the first time) so I disregarded that as a cause. I must have tried it on a faulty PCB though; when giving it another go on another pcb it worked!

Anyone who'd like to use the Kicad files; please feel free to use them to your liking; they work like a charm! (Do need to fit another LDO though)