Uno R4 · pot-controlled DAC sine

Turn the pot to change the A1 ADC reading and the A0 DAC sine amplitude. Probe A0 in Scope. The real DAC clips near the supply limits; the official core also briefly releases its output between updates.

What's on the bench

• Arduino Uno R4
• Battery
• Resistor
• Trim Pot

How it's wired

• Battery · pos→Arduino Uno R4 · 5v
• Battery · neg→Arduino Uno R4 · gnd
• Arduino Uno R4 · 5v→Trim Pot · a
• Arduino Uno R4 · gnd2→Trim Pot · b
• Trim Pot · wiper→Arduino Uno R4 · a1
• Arduino Uno R4 · a0→Resistor · a
• Resistor · b→Arduino Uno R4 · gnd2

The code

This Arduino C++ sketch lives in the Code tab; sign in and press Compile & upload to build real firmware for the emulated board.

// SPDX-License-Identifier: MIT
// First-party UNO R4 example: A1 sets the amplitude of the A0 DAC sine.
static const int16_t kSine[] = {
  0, 399, 783, 1137, 1447, 1702, 1891, 2008,
  2047, 2008, 1891, 1702, 1447, 1137, 783, 399,
  0, -399, -783, -1137, -1447, -1702, -1891, -2008,
  -2047, -2008, -1891, -1702, -1447, -1137, -783, -399
};
void setup() {
  Serial.begin(115200);
  analogReadResolution(14);
  analogWriteResolution(12);
}
void loop() {
  const int level = analogRead(A1);
  Serial.print("adc14 ");
  Serial.println(level);
  for (int16_t sample : kSine) {
    const int code = 2048 + (int32_t)sample * level / 16383;
    analogWrite(DAC, code);
    delay(1);
  }
}

Firmware licence

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