Arduino Code

#include <SPI.h>

// set pin 7 as the slave select for the digital pot:
const int CS = 7;

void write_reg(uint16_t addr, uint16_t data) {
    digitalWrite(CS, LOW);
    addr = addr | 0x80;
    SPI.transfer(addr);
    SPI.transfer(data);
    digitalWrite(CS, HIGH);
}

void read_reg(uint16_t addr, uint8_t *rx_data) {
    digitalWrite(CS, LOW);
    addr = addr & 0x7F;
    SPI.transfer(addr);
    *rx_data = SPI.transfer(rx_data);
    digitalWrite(CS, HIGH);
}

void setup() {
  Serial.begin(115200);
  pinMode(CS, OUTPUT);
  digitalWrite(CS, HIGH);
  // initialize SPI:
  SPI.begin();
}

void loop() {
  static int i = 0;
  uint8_t temp;
  write_reg(0x00, i);
  read_reg(0x00, &temp);
  Serial.println(temp);
  delay(250);

  if(++i > 5){
    i = 0;
  }
}