I2C Pullup resistors

I have an GY-521 breakout board with 2K2 pull-up resistors to 3.3V. I want to use a level shifter with it, I know it is not necessarily required but it would make me feel better :stuck_out_tongue: Anyway, I was thinking of using the PCA9306D chip and was wondering what pull-up resistors I need, if I need them at all.

On the other side of the level shifter, do you mean?

Well on the other side, the 5v side, I would assume I would use 4k7 resistors as that seems to be the most common value for I2C. What I want to know is if I need other pull up resistors on the 3.3V side, from the breakout board, as it already has 2k2 resistors. I have read that 2k2 isn't the best resistor for the job and so I was thinking I could add another resistor or even replace the ones on the board to be 4k7. Hopefully I am not over thinking this, I just want the board I am making to work without issues.

Youโ€™re overthinking it. Leave them alone. :slight_smile:

See this page:

At 5V at least, 2.2K was fine:

Sweet, thanks for that page, its a treasure trove of information. So I will go ahead and just hook my breakout board directly to the 3.3v side and use 4k7 resistors on the 5V side. Thanks for the help, it has been invaluable.