SDA_1 and SLA_1 pins of OpenCM 9.04

Hi everyone, I would like to use I2C communication between arduino UNO and OpenCM. Actually the problem is the OpenCM already connected with OpenCM485 exp board which communicates through Serial3 (D24, D25) OpenCM485 EXP DXL Port. In the manual (OpenCM),the SDA_2 (25) SCL_2 (24) pins are mentioned clearly. However, I couldn’t find the SDA_1 SCL_1 pins. Might be the OpenCM does have just single I2C connection not very sure…

thanks in advance if anyone can help.

When I dug into the variant.h and variant.cpp files for the OpenCM-904, I found the following info:


variant.h seems to say that there is only one I2C port defined (Line 150).

variant.cpp seems to say that I2C1 Port is linked up to Pins 13 and 14 (Lines 90-91), but that Pin 14 is used for the LED. Don’t know if you can override that setting. @Tech_Support may know more.

Do you use Serial2 on OpenCM-904 for anything? Maybe you can hook up this Serial2 to the UART Port on the UNO, if you have not used it for something else already?

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@roboteer Hi, I appreciate you comments and suggestions, thanks a lot

Right, it seems OpenCM has only one I2C

Yes, I do wait for further confirmation about these pins. Might these pins can be used somehow…

Yes, UART1 pins are free so Seriel2 can be hooked up to the UNO, but I am looking to use I2C1 port if it can be used. If not then definitely will go with this option.