DanKoloff
commented
5 months ago This is not an issue to fix. Just we designed the board to be suitable for two types of ESP32 modules - with or without PSRAM (our ESP32-POE and ESP32-POE-ISO modules are designed in the same manner).
The ESP32 module without PSRAM is ESP32-WROOM and the ESP32 module with PSRAM is called ESP32-WROVER.
By default in ESP32-POE2 design we place the ESP32-WROVER module with PSRAM.
The difference between ESP32-WROOM and ESP32-WROVER modules is that the ESP32-WROVER uses two of the GPIOs for the PSRAM (GPIO16 and GPIO17). So in boards with ESP32-WROVER module (like ESP32-POE2) - Ethernet clock is GPIO0 instead of GPIO17 and GPIO33 is routed to the UEXT (instead of GPIO16).
So if you have problems with Ethernet - make sure that in your code - clock is set to GPIO0.
If you want to use GPIO16 at the UEXT, consider that GPIO16 is replaced by GPIO33 and use GPIO33 in the code (instead of GPIO16).
Using the ESP-POE2 board and Olimex BME280 board I tried the simple example provided by Olimex (https://github.com/OLIMEX/ESP32-POE/blob/master/SOFTWARE/ARDUINO/ESP32_PoE_MOD_BME280/ESP32_PoE_MOD_BME280.ino), the I2C communication with BME280 does not work. Using a protocol analyser I see data on SDA (GPIO13) but SCL (GPIO16) is always HIGH.
Moving forward with my investigation, I look at ESP-POE2 schematic and see the following connection :
Can somebody explain why is this here ?
So I tried to replace SCL pin with GPIO5, and tada ! It works. It is not really a solution in itself because your UEXT connectors uses GPIO16 for SCL.
Last test was to remove R19, and still did not work. I finally stumbled on this piece of information :
And that seems to be the answer. It's a bit confusing that this exact pin was chosen for UEXT SCL pin... Any plan to fix this ?