T-Eth-POE

The LilyGO-T-Eth-POE board is not shown in the boards list in the Arduino IDE. It uses an ESP32 WROOM Module, so you select the ESP32 Wrover from the boards list.

While testing the POE the example code didn't work. Specifically, the ethernet never connected. After some digging it turned out that the #defines in the example code use "SYSTEM_EVENT_ETH_CONNECTED" etc. The include from WiFi.h uses "ARDUINO_EVENT_ETH_CONNECTED". A quick global search and replace of SYSTEM with ARDUINO got everything working just fine.

The latest version of the library checks versions and selects the correct #define for you.

To use I2C with these ESP32 modules you're likely to need to map some GPIO pins to the I2C bus. These new pin definitions are then passed to the Arduino Wire library begin function in setup. You must take care to use pins that are I/O rather than Input only. Check the datasheet. Pins 21/22 are the Arduino default for SDA/SCL I2C, but the POE board doesn't break out those pins.

For example, on the POE board the expansion connector is:

Pin	Function	Pin	Function
36	Input	39	Input
34	Input	35	Input
16	Input/Output	32	Input/Output
33	Input/Output	12	Input/Output
04	Input/Output	15	MOSI
02	MISO	14	SCLK

So to use I2C we must select two pins and pass that to the Wire library. We can't use the top four pins (36,39,34,35) because they're input only. There are three pins used for SPI (02,14,15) so they're also not available. Any of the remaining pins can be used (16,32,33,12,04).

The code would include something like this:

#include <Wire.h>

// Pins used for i2c
#define I2C_SDA 33
#define I2C_SCL 32

void setup()
{
  Wire.begin(I2C_SDA,I2C_SCL);
}