🛠 Lire un capteur analogique sur A0-A7

Objectives

Read an analog voltage using the ATmega4809's 10-bit ADC. The Nano Every exposes 8 analog inputs A0 to A7 on its connector (the chip supports 14 channels in total), converted between 0 and the reference voltage (5 V by default).

Hardware

• 1 × Arduino Nano Every
• 1 × 10 kΩ potentiometer (or analog sensor: LDR + resistor, flex sensor…)
• 3 × jumper wires
• Micro-USB cable

Complete code

// Lecture du potentiometre sur A0 + allumage seuil sur LED 13
const uint8_t CAPTEUR = A0;
const uint16_t SEUIL = 512;
uint32_t derniereImpression = 0;

void setup {
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(9600);
}

void loop {
  uint16_t brut = analogRead(CAPTEUR);          // 0..1023
  float tension = brut * (5.0 / 1023.0);        // 0.00..5.00 V

  if (millis - derniereImpression >= 100) {   // 10 Hz
    derniereImpression = millis;
    Serial.print("brut="); Serial.print(brut);
    Serial.print("  U="); Serial.print(tension);
    Serial.println(" V");
  }
  digitalWrite(LED_BUILTIN, brut > SEUIL ? HIGH : LOW);
}

Expected verification

Potentiometer: cursor towards GND → reading close to 0; towards 5 V → close to 1023. LED 13 turns on above half the range. The serial monitor displays raw values and voltage at 10 Hz.

Common errors

• Reading a digital pin as analog: only A0-A7 are ADC inputs on the connector.
• Expecting 1024: the 10-bit ADC ranges from 0 to 1023, hence dividing by 1023 and not 1024.
• Unconnected input: a floating ADC pin gives drifting values — always provide a path to GND.
• Printing speed: printing on every loop floods the monitor; throttle with millis as shown above.
• I²C on this board is NOT on A4/A5 by default (Wire bus on dedicated SDA/SCL pins): if you are reusing a classic Nano schematic, check this point carefully before adding an I²C sensor.