I am using PMOD (differential JD1) for I2C communication (SDA, SCL). I only have one board so I don't want to accidently damage my zed board. In order to decide the value of pull-up resistors, I have to know the maximum allowed current for PMOD. Folks said normally pull-up resistors should be around 4.7k ohm and smaller resistors are better. (https://learn.sparkfun.com/tutorials/i2c/all).