ESP8266 Arduino Core Interface ADC

ADC

Required

• Required Hardware – ESP8266 with Programmer (or)  NodeMCU Dev Kit
• Required Software Tools  – Arduino IDE with ESP8266 Core

Circuit of ESP8266 Arduino Core ADC

Code

/* 
  http://www.ArunEworld.com/Embedded/ESPressif/ESP8266/ESP8266_Arduino-Core/
  Tested By  : Arun(20170219)
  Example Name : AEW_ADC-Interface.ino
 */
 /*
  AnalogReadSerial
  Reads an analog input on pin 0, prints the result to the serial monitor.
  Graphical representation is available using serial plotter (Tools > Serial Plotter menu)
  Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

  This example code is in the public domain.
*/

// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  int sensorValue = analogRead(A0);
  // print out the value you read:
  Serial.println(sensorValue);
  delay(1);        // delay in between reads for stability
}

 

Result of ESP8266 Arduino Core ADC

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Code Explanation – AEW_ADC-Interface.ino

1. Header Comment

/* 
  http://www.ArunEworld.com/Embedded/ESPressif/ESP8266/ESP8266_Arduino-Core/
  Tested By  : Arun(20170219)
  Example Name : AEW_ADC-Interface.ino
 */

• This is just documentation:
  • Source/author’s site
  • Date of testing (2017-02-19)
  • Example name

---

2. Example Purpose

/*
  AnalogReadSerial
  Reads an analog input on pin 0, prints the result to the serial monitor.
  Graphical representation is available using serial plotter (Tools > Serial Plotter menu)
  Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

  This example code is in the public domain.
*/

• It explains what the sketch does:
  • Reads analog values from pin A0 (the ESP8266 has only one ADC input).
  • Sends the value to the Serial Monitor / Serial Plotter.
  • Suggests using a potentiometer as input (center pin → A0, sides → 5V & GND).
  • Declares that this example is free to use (public domain).

---

3. Setup Function

void setup() {
  Serial.begin(9600);
}

• setup() runs only once when the ESP8266 boots or resets.
• Serial.begin(9600); initializes serial communication at 9600 baud rate.
• This allows the ESP8266 to send ADC readings to your PC via USB.

---

4. Loop Function

void loop() {
  int sensorValue = analogRead(A0);
  Serial.println(sensorValue);
  delay(1);
}

• loop() runs continuously after setup.

Step by step:

1. analogRead(A0);
   • Reads the voltage at pin A0.
   • The ESP8266 ADC converts this voltage (0–1V in NodeMCU, though some boards have onboard voltage dividers to allow 0–3.3V).
   • Returns an integer value (range: 0–1023).
2. Serial.println(sensorValue);
   • Prints the value to the Serial Monitor (so you can see numbers like 0–1023).
   • Or you can visualize it as a waveform in the Serial Plotter.
3. delay(1);
   • Adds a 1 ms delay to stabilize readings and avoid overwhelming the serial output.

---

What It Does in Real Life

• If you connect a potentiometer:
  • Rotating the knob changes voltage at A0.
  • Serial Monitor shows values changing from 0 (0V) to 1023 (~1V or ~3.3V depending on board).
• Useful for testing sensors like LDR, temperature sensors, etc., since many provide analog outputs.