nRF52832 TWIM Pull-up Value

[webzoid]

How can I determine the correct value pull-up resistor to be used on the TWIM port?

The nRF52832 reference documentation mention an internal 13k pull-up however I've always used significantly stronger pull-ups - 4k7 and 1K in some instances.

Unless I'm missing something, the documentation also skips over this too.

[MartinBL]

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.