Tutorial

This tutorial generates two triangular waves out of phase by the dual digital pot to demonstrate its

basic usage. The two internal digital pot POT0 and POT1 server as voltage divider with terminal A

connected to VCC and terminal B connected to GND. We use Arduino UNO R3 to control the

terminal W0 of POT0 to change it from min to max (Dn: 0 -> 255) every 1 ms and then in reverse,

from max to min (Dn: 255 -> 0). On the contrary, the terminal W1 of POT1 will be changed from max

to min (Dn: 255 -> 0) every 1 ms and then in reverse, from min to max (Dn: 0 -> 255). Two channels

CH1 and CH2 of the oscilloscope will be used to observe the voltage of W0 and W1 respectively to

check whether all the possible taps are available.

Basic Principle

This breakout employs MCP42100, which has two individual digital potentiometer POT0 and POT1

corresponding to two groups of terminals A0, B0, W0 and A1, B1, W1. Similar to the mechanical

potentiometer, terminal A and B can be taken as two pins of a resistor (the nominal resistance is

Rab=100KΩ) while terminal W is the wiper. The wiper can be changed to one of the 256 positions

evenly distributed between A and B. The wiper is reset to the mid-scale position (Dn=128,0x80)

upon power-up.

To change the position of the wiper W, two byte should be sent. The first byte is the command to

determine which pot to be selected. The second byte is the data to determine the position of the

wiper. This byte is also denoted as Dn. When Dn=0, terminal B is connected to W. When Dn=255, W

is changed to the closest position to A. For example, to set W0 of POT0 to the position of 100,

Arduino should first sends 0x11 (Write data, select POT0) and then 0x64 (=100, decimal) through

the SPI.