I2C with ESP32-POE

[espethuser]

I'm using the ESP32-POE with ethernet, both for power and communication. I'm struggling a bit for free I/O pins, so taking the Olimex advice:

If you need more GPIO pins consider either using additional GPIO expander board over I2C/SPI/UART

I bought an MCP23008. But I'm a bit confused which pins I should use it with. This chap seems to have used the ESP32-POE-ISO with both ethernet and I2C, but when I look at the I2C pins, 16 seems to be used by both EMAC_CLK_OUT_180 and EMAC_RX_ER so I don't really understand how that's working successfully for him.

Guidance would be really appreciated, thank you!

[LubOlimex]

Pins 13 and 16 are alright. Don't forget the GND. We have published examples of ESP32-POE with I2C modules at the Arduino software section here:

https://github.com/OLIMEX/ESP32-POE/tree/master/SOFTWARE/ARDUINO

MOD-BME280 uses I2C:

https://github.com/OLIMEX/ESP32-POE/blob/master/SOFTWARE/ARDUINO/ESP32_PoE_MOD_BME280/ESP32_PoE_MOD_BME280.ino

MOD-IO uses I2C:

https://github.com/OLIMEX/ESP32-POE/blob/master/SOFTWARE/ARDUINO/ESP32_PoE_WebServer_MOD_IO/ESP32_PoE_WebServer_MOD_IO.ino

there are few others there too.

[espethuser]

Pins 13 and 16 are alright.

Thank you I'm confused how pin 16 is usable when it is used by both emac_clk_out_180 AND emac_rx_er? Just don't understand enough! :-)

[LubOlimex]

I think you are confusing ESP32 pin #16 and GPIO #16 which is ESP32 pin #27.

The Arduino code doesn't care about ESP32 pin #; only about GPIO#.

[espethuser]

Are you sure I'm confusing my pins??

Here the ESP32-POE clearly shows that GPIO pin 16 is used by both emac_clk_out_180 AND emac_rx_er?

Pin 13 [is] alright.

GPIO Pin 13 is pulled up to 3v??

This board sure is hard to work with! :-)

[LubOlimex]

Better download and use the schematic export to track these. Here:

https://github.com/OLIMEX/ESP32-POE/blob/master/HARDWARE/ESP32-PoE-hardware-revision-K/ESP32-PoE_Rev_K.pdf

Yes, both GPI)16 and GPIO13 are pulled up. This is for I2C compatibility sake. You can pull them down or remove the resistor that connects them to 3.3V.