#define DAC_PIN 25

void setup() {
  Serial.begin(115200);
  Serial.println("dacWrite started");

  pinMode(DAC_PIN, OUTPUT);
}

void loop() {
  for (uint8_t i = 0; i < 16; i++) {
    uint8_t v = i*16;
    Serial.printf("dacWrite(%d)\n", v);
    dacWrite(DAC_PIN, i*16);
    delay(1000);
  }
  Serial.println("dacWrite(255)");
  dacWrite(DAC_PIN, 255);
  delay(1000);
}