GPIO16 and GPIO17 not available on ESP32-DevKitC board with ESP32-WROVER-(I)E module (8MB)

[Solarteur]

As a quick interim solution before switching to ESP32-S3, I wanted to replace an ESP32-DevKitC board with ESP32-WROOM module (4MB) in my openDTU-OnBattery system with an ESP32-DevKitC board with ESP32-WROVER-(I)E module (8MB) - according to the labeling of the connection pins, this should be possible 1:1.

In practice, this did not work in my case. When troubleshooting, I found here in the “Header Block” section

https://docs.espressif.com/projects/esp-dev-kits/en/latest/esp32/esp32-devkitc/user_guide.html

the following note :

"3(1,2) The pins GPIO16 and GPIO17 are available for use only on the boards with the modules ESP32-WROOM and ESP32-SOLO-1.
The boards with ESP32-WROVER modules have the pins reserved for internal use."

It's a shame that I use GPIO16 and GPIO17 for the nRF24L01+ module on my board...

[schlimmchen]

Thanks, I will add this to the docs eventually!

I am planning to fiddle with these kinds of updates as well, i.e., I have some ESP32 (non-S3) modules, which I am going to solder onto existing DevKits with modules that only have 4MB of flash. Was going to add info about this to the docs.

[Solarteur]

Replacing the ESP32 WROOM (4MB) with the ESP32 WROVER (8MB) went better than expected:

• desoldering with a hot air dryer and a very thin stainless steel sheet ("eraser template") that was pushed between the solder connections,
• remaining solder removed with solderwick,
• precisely aligned, fixed with a sturdy clothespin and
• soldered with a "normal" ERSA 25 soldering iron and extra flux.

[schlimmchen]

You do need hot air, that's for sure. When using a hot air gun without temperature control, you have to be very careful not to overheat the board or components. It seems you did well, as the board probably still works, otherwise you would have told us?

precisely aligned, fixed with a sturdy clothespin

Yeah, that is actually a good idea! What I usually do is solder one pad, align while heating the solder, then solder one other pad in the opposite corner of the part.

What you did not mention is that the GND pads underneath the module are not soldered if you do it like this. That's not ideal, but they might only be there for thermal conductivity, in which case the drawbacks are not too big of a concern.

I think you should be proud, that is not an easy task to accomplish. Good job 🚀