dac-analogique.ino
The R4 carries a true 12-bit DAC on A0: it outputs a clean continuous voltage, unlike filtered PWM on AVRs. This script generates a sinusoidal ramp steerable on the fly from the serial monitor.
Hardware
An Arduino UNO R4 Minima (Renesas RA4M1, Cortex-M4 @ 14 MHz, 5 V, 12-bit DAC, no radio) powered by USB or 6-24 V. A multimeter to verify, or an analog input to drive (0-3.3 V).
Wiring
A0 to the input to drive; common grounds. 3.3 V full-scale output, low output current (buffer it to drive a load).
How it works
analogWriteDAC0() writes straight into the RA4M1 integrated digital-to-analog converter; the output voltage follows the value in real time, with no PWM ripple.
Running it
Arduino IDE 2.x (with the « Arduino UNO R4 Boards » core installed), pick « Arduino UNO R4 Minima », select the port and Upload. The serial monitor runs at 9600.
Variants
Generate waveforms (triangle, sawtooth) for a synth, or drive a motor setpoint through an amplifier stage.
dac-analogique.ino
// DAC 12 bits integration du R4 : tension continue sur A0.
// analogWriteDAC0(valeur) : 0..4095 pour 0..3,3 V.
// A verifier a l'ohmmetre/metre : A0 -> metre, GND commun.
void setup() {
Serial.begin(9600);
Serial.println(F("DAC0 sur A0 : 0..4095 -> 0..3,3 V"));
Serial.println(F("Envoyez une valeur, ou 'r' pour un rampe."));
}
void loop() {
static float phase = 0;
// Petite rampe triangulaire 0..3,3 V visible au metre.
phase += 0.02;
float x = 0.5 + 0.5 * sin(phase);
int valeur = (int)(x * 4095);
analogWriteDAC0(valeur);
static unsigned long t0 = 0;
if (millis() - t0 >= 500) {
t0 = millis();
Serial.printf("DAC=%d U=%.3f V\n", valeur, valeur * 3.3 / 4095.0);
}
// Commande serie : 's' suit une consigne saisie.
if (Serial.available()) {
int consigne = Serial.parseInt();
if (consigne >= 0 && consigne <= 4095) {
analogWriteDAC0(consigne);
Serial.printf("force a %d (%.3f V)\n", consigne, consigne * 3.3 / 4095.0);
}
}
}