what function do these resistors play in the i2c circuit?
but 30k Ohms seems very high for the pull-up resistors.
Hi, Technically they're just pullup resistors - so I suspect 33K will be just fine. Most of the time I just 10K, but since we're dealing with 3.3v and not the normal 5v there might be a reason for a higher value. ...In fact, I think I might have used 33K the last time around - for the same reason as you. Steve
but you think 3k would be better suited?
The value of the [pull-up] resistors is not critical. I have seen anything from 1k8 (1800 ohms) to 47k (47000 ohms) used. 1k8, 4k7 and 10k are common values, but anything in this range should work OK. I recommend 1k8 as this gives you the best performance. If the resistors are missing, the SCL and SDA lines will always be low - nearly 0 volts - and the I2C bus will not work.
But the practical effect of that here will be minimal.
so a larger resistor will give you a more efficient circuit