ESP32 Forum

I just tested the I2C port for the first time on my Lolin D32 PRO board and found that it supplies NEGATIVE VOLTAGE to the I2C port!!! I used a standard I2C cable from Adafruit and when I connected it to my Adafruit Seesaw board it got very hot and didnt power up so I then connected the cable to a breadboard I2C port adapter and using a voltmeter found that the supply voltage is actually 3.3V!!! I tried to find a contact for Lolin/Wemos but couldn't really find anything so if you know how to please let me or them know.

That would be very surprising, as that board does not to have any components that are capable of inverting the input voltage. How did you measure this?

The schematic for the board shows the port pinoit is different from the standard stemma I2C port. I am so effing annoyed at the lack of standardization among hardware and code for arduino.

Pinout. Why cant you edit your own posts on this forum?

There's no native pins for I2C. You can assign whatever pins you want to a Wire object bus. The author of arduino-esp32 has provided some suggested pins in the variant file. The bus needs pull-up resistors on the pins (maybe more than what the internal iomux can supply), so if you measure the voltage on an active bus, it will be high during idle periods.

You dont know what your talking about. I am talking about the I2C port on the board, its a 4-pin JST SH 1.0 connector. Typically known as Stemma QT or Qwiic by adafruit and sparkfun respectively.

found that the supply voltage is actually 3.3V!!!

Of course it is. Why wouldn't it?

You dont know what your talking about.

But now you have learned a lesson: Never just assume that different vendors use the same pinout for their proprietary connections; always check the documentation before plugging things together.

Yeah it was missing a minus sign. something I could have changed if you could edit your own posts. What I learned is that Lolin and Arduino sucks.

On PC, I can edit my posts ("pen" button at the top-right of the post). The mobile version of the forum seems a little broken.