• This library lets you control the WMS7202 series digital potentiometers with ease. Examples:
  • WMS7202050P
  • WMS7202100P
• Datasheet link: https://www.digikey.ca/htmldatasheets/production/836814/0/0/1/wms7202.html
• You can communicate with the chip using the SPI.

• It is a dual channel digital potentiometer.
• It comes with different values, e.g. 50kOhm, 100 kOhm.
• It has a non-volatile memory which can be used to store up to 4 different values per channel.
• All potentiometers are loaded with the value stored in the NVMEM position 0 for their respective channel on power up.

You can find more info on these in the datasheet in section 7.7

//Software reset the part to the power up state 
void reset();

// Discontinue clock supply to  the logic and memories 
void sleep();

//Clock supply to the logic and memories,
//you need to call this after powering up before any other operation can be performed
void wakeUp();

//Increment tap register value by one 
void increase(byte TR);

//Decrement tap register value by one 
void decrease(byte TR);

//Load the selected NVMEM location into the tap register 
void loadTRFromNVMEM(byte TR, byte slot);

//Takes the current potentiometer settings and saves in the selected NVMEM location. 
void writeTRToNVMEM(byte TR, byte slot);

//Writes a value to the tap register of the selected channel 
void writeToTR(byte TR, byte wiperPosition);

//Writes a value to the selected NVMEM register of the selected channel 
void programNVMEM(byte TR, byte slot, byte value, int outputBufferMode);

//Erases the 9 bit word stored at the specified NVMEM location.
void eraseNVMEM(byte TR, byte slot);

//Read and return the value of the selected NVMEM location. 
//by passing a pointer, outputBufferMode acts as an output parameter.
int readNVMEM(byte TR, byte slot, int* outputBufferMode);

// Read the value of the selected tap register 
int readTapRegister(byte TR);

WMS7202 digitalPot(D8);
...
SPI.begin();
digitalPot.wakeUp();
...
digitalPot.writeToTR(digitalPot.potA, 230);
...
digitalPot.increase(digitalPot.potA);
...

• The pinout can be found in section 5. of the datasheet.
• In order for the memory functionalities to work, you need to supply WP pin with Vdd (connect WP pin to the supply voltage)
• The SDO pin also has to be pulled up in order for the data to be read. I used a 10kOhm resistor between Vdd and SDO for this.

• I have never managed to get the R/B pin working. It is supposed to be pulled up, and it should indicate when the chip is ready to accept more commands. For the memory operations I have introduced a delay of 2ms instead of using this pin.
  • This value can be also found in the datasheet in Table 10 - Timing parameters as the value for "Store to NVMEM Save Time". This didn't introduce any performance penalty for my applications, but it is something to be aware of.
• There is also a small delay in the reading operations as well. It is 1ms.