We are trying to solve a problem which means we are unable to communicate over I2C on our Xavier NX/Nano based carrier board design. Upon I2C Bus Analysis, we have found there is a difference between I2C Logic Levels on Nano SOM and Xavier SOM.
- Custom Carrier Boards are the same.
- I2C transactions are monitored through Oscilloscope. These transactions are conducted over I2C2_SCL/SDA - Pin 232 and 234.
- Resistance between 1.8V and I2C2_DAT/CLK pins are same = 1.3kohm after connecting any of the SOMs - Xavier SOM and Nano SOM
I2C Transaction as monitored on Nano SOM + Custom Carrier Board
I2C Transaction as monitored on Xavier SOM + Custom Carrier Board
- We notice that I2C signals on Xavier SOM + Custom Carrier Board setup are not pulled fully down.
- This introduces some problems with our devices as it leaves the devices confused about the state. Below is an example of how the I2C bus is then left hanging in inappropriate state -
- We don’t see this problem on Nano SOM + Custom Carrier Board setup. I2C Transactions are normal, and without any errors. There is almost no difference in pull up resistors in Xavier SOM and Nano SOM and no changes on our carrier board setup.
Any suggestions about how to resolve this or what could cause this issue are greatly appreciated.