RE: nRF52832 TWIM Pull-up Value

MartinBL — Fri, 13 Jul 2018 11:39:54 GMT

Hi,

There is no definite answer to what value you should use. It depends on what frequency you are using and the total capacitance on the bus which in turn depends on the PCB trace/wire lengths, widths, grounding, etc.

You want the pull-ups strong enough to force a clean signal, but not too strong, because then the resistors would start drawing unnecessary currents when the signals are low. To find the sweet spot it might be easiest just to use an oscilloscope and experiment with different values. Look at the waveforms and decide on values that doesn't slow down the rise/fall times too much. If you have equipment for measuring the bus capacitance you can use formulas as discussed here.