VI I2C Logic level and pullup resistors


I’m using the mipi adapter board provide by leopard imaging and trying to hook up my own camera board. When I’m loading my driver it fails at the point where it is trying to get an i2c acknowledge from my camera. This is not suprising as I haven’t implemented the complete i2c stack on the camera side. However, in order to better understand, I hooked the i2c signals to a logic analyzer and i wanted to see if the jetson is actually doing the right thing. However, I observed unexpected beahviour. SDA is high and SCL is always low. This makes me wonder about some basic requirements of the interface. Is the logic level of the vi-i2c (i believe i’m using channel 0) 1.8V? Do I require external pullup resistors? I coulnd’t find any pullup resistors in the schematics of the carrier board nor the camera board so I was expecting that it uses some sort of internal pullup resistors…

Actually, I just have found part of the answer to my question in the OEM Product Design Guide:

  • Logic level of the I2C-VI is 1.8V
  • There are 1K pullup resistors on the Jetson module

But now I wonder why I observe this strange behavior of SCL being always low… How can I make sure I didn’t break something by mistake?

Are you measuring SCL with camera connected? If so, SCL could be pull down by camera.

I also get an SCL signal now. Turned out, that I was using a broken probe…