I'm using the MCP4131 digital potentiometer to control the brightness of a LED using an Arduino Uno. The MCP4131's interface is SPI and it has a multiplexed SDI/SDO pin (pin #3).
The datasheet specifies a resistor R1 to be placed on the host's SDO before the host SDI/SDO signal are being multiplexed. I was wondering how to calculate it's value? For now, I used a 1k resistor and it works but I want to learn how to deduce this value from the datasheet.
The comment says that R1 must be sized to ensure VIL and VIH of the devices are met, I can't figure out what these are.
If anyone can explain I'll appreciate it, thank!