ESP32-C6-EVB wrong SDA and SCL?

Started by MrB, December 27, 2023, 03:04:14 PM

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Hi there,

it was a nightmare to find out that SDA is on pin GPIO7 and SCL is on pin GPIO6 - you have to update your docs.
With Wire.begin(7,6) everything works fine.

This is the first time I am a little bit disappointed of Olimex. Never had such problems.

All the best from German


I guess you used pins #5 and #6 of the UEXT (which are respectively GPIO7/SCL and GPIO6/SDA). At the UEXT SDA is actually GPIO6 and SCL is GPIO7. But it doesn't really matter any free GPIO can be used for SDA or SCL, the chip has fine multiplexing.

Anyway, I believe it is easily visible in the schematic:

Technical support and documentation manager at Olimex


This is what I mean. When I try to use I2C with SCL on 7 and SDA on 6 it does not work.

I tried

Wire.begin() and
BOTH do not work... and yes, I wired it correctly. I checked it 139² times ;)


This is strange. It should work with Wire.begin(6,7) - at least it does here. We tested and it seems ESP32-C6-EVB is working as intended. The I2C lines at the UEXT are working properly and according to the schematic. We empirically tested with one of our simpler I2C modules - MOD-RTC2.

Search for the culprit of your issues elsewhere.

What I2C module are you using? Maybe it has wrong markings about SCL and SDA? Maybe you cross connect it?

What software are you using? Is it possible that the software or the software configuration has improper pinout, incompatible with ESP32-C6-EVB?

What is the package and the version that you use?

If you are using the official ESP32 package for Arduino IDE, make sure to select our board from the board selector, it has own entry in the package ("Olimex ESP32-C6-EVB"), here is the config:

Technical support and documentation manager at Olimex


Ok --- I am 100% braindead... I took the board and the schematic in same direction - so I can read the texts normally. But the UEXT is flipped ;) When I rotate the schematics by 180° it works... Oh my god... I feel so incompetent

Thank you for giving me some input to find the problem - and sorry for taking your time ;(


No worries, things like this happen. I was thinking about that maybe you mirrored the UEXT orientation. Take a look here for future reference:
Technical support and documentation manager at Olimex