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Experiment # 4: ESP32 ADC - Read Analog Values With Arduino IDE

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Wasiq Bhatti

This document describes an experiment using the analog to digital converter (ADC) on the ESP32 to read analog voltage values from a potentiometer. It explains that the ESP32 ADC returns values from 0 to 4095 that correspond to voltages from 0 to 3.3V, though the mapping is nonlinear. It provides code to read the value of a potentiometer connected to GPIO pin 34 and print it to the serial monitor. Rotating the potentiometer causes the printed values to change, demonstrating reading analog values with the ESP32 ADC.

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Experiment # 4: ESP32 ADC - Read Analog Values With Arduino IDE

Uploaded by

Wasiq Bhatti
189 views6 pages
This document describes an experiment using the analog to digital converter (ADC) on the ESP32 to read analog voltage values from a potentiometer. It explains that the ESP32 ADC returns values from 0 to 4095 that correspond to voltages from 0 to 3.3V, though the mapping is nonlinear. It provides code to read the value of a potentiometer connected to GPIO pin 34 and print it to the serial monitor. Rotating the potentiometer causes the printed values to change, demonstrating reading analog values with the ESP32 ADC.

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This document describes an experiment using the analog to digital converter (ADC) on the ESP32 to read analog voltage values from a potentiometer. It explains that the ESP32 ADC returns values from 0 to 4095 that correspond to voltages from 0 to 3.3V, though the mapping is nonlinear. It provides code to read the value of a potentiometer connected to GPIO pin 34 and print it to the serial monitor. Rotating the potentiometer causes the printed values to change, demonstrating reading analog values with the ESP32 ADC.

Copyright:

© All Rights Reserved
Download as PDF, TXT or read online from Scribd
Download as pdf or txt
189 views6 pages

Experiment # 4: ESP32 ADC - Read Analog Values With Arduino IDE

Uploaded by

Wasiq Bhatti
This document describes an experiment using the analog to digital converter (ADC) on the ESP32 to read analog voltage values from a potentiometer. It explains that the ESP32 ADC returns values from 0 to 4095 that correspond to voltages from 0 to 3.3V, though the mapping is nonlinear. It provides code to read the value of a potentiometer connected to GPIO pin 34 and print it to the serial monitor. Rotating the potentiometer causes the printed values to change, demonstrating reading analog values with the ESP32 ADC.

Copyright:

© All Rights Reserved
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Embedded Systems Laboratory 1

Experiment 4

Experiment # 4:
ESP32 ADC – Read Analog Values with
Arduino IDE
Analog Inputs (ADC)

Reading an analog value with the ESP32 means you can measure varying
voltage levels between 0 V and 3.3 V.

The voltage measured is then assigned to a value between 0 and 4095, in


which 0 V corresponds to 0, and 3.3 V corresponds to 4095. Any voltage
between 0 V and 3.3 V will be given the corresponding value in between.

ADC is Non-linear

Ideally, you would expect a linear behavior when using the ESP32 ADC pins.
However, that doesn’t happen. What you’ll get is a behavior as shown in the
following chart:
Embedded Systems Laboratory 2
Experiment 4

This behavior means that your ESP32 is not able to distinguish 3.3 V from 3.2
V. You’ll get the same value for both voltages: 4095.

The same happens for very low voltage values: for 0 V and 0.1 V you’ll get the
same value: 0. You need to keep this in mind when using the ESP32 ADC
pins.

analogRead() Function

Reading an analog input with the ESP32 using the Arduino IDE is as simple
as using the analogRead() function. It accepts as argument, the GPIO you
want to read:

analogRead(GPIO);
Embedded Systems Laboratory 3
Experiment 4

The ESP32 supports measurements in 18 different channels. Only 15 are


available in the DEVKIT V1 DOIT board (version with 30 GPIOs).
Grab your ESP32 board pinout and locate the ADC pins. These are
highlighted with a red border in the figure below.

These analog input pins have 12-bit resolution. This means that when you
read an analog input, its range may vary from 0 to 4095.

Note: ADC2 pins cannot be used when Wi-Fi is used. So, if you’re using Wi-Fi and you’re having
trouble getting the value from an ADC2 GPIO, you may consider using an ADC1 GPIO instead, that should
solve your problem.
Embedded Systems Laboratory 4
Experiment 4

Read Analog Values from a Potentiometer with ESP32

To see how everything ties together, we’ll make a simple example to read an
analog value from a potentiometer.

For this example, you need the following parts:

 ESP32 DOIT DEVKIT V1 Board


 Potentiometer
 Breadboard
 Jumper wires

Schematic

Wire a potentiometer to your ESP32. The potentiometer middle pin should be


connected to GPIO 34. You can use the following schematic diagram as a
reference.
Embedded Systems Laboratory 5
Experiment 4

Code

// Potentiometer is connected to GPIO 34 (Analog ADC1_CH6)


const int potPin = 34;

// variable for storing the potentiometer value


int potValue = 0;

void setup() {
Serial.begin(115200);
delay(1000);
}

void loop() {
// Reading potentiometer value
potValue = analogRead(potPin);
Serial.println(potValue);
delay(500);
}

This code simply reads the values from the potentiometer and prints those
values in the Serial Monitor.

In the code, you start by defining the GPIO the potentiometer is connected to.
In this example, GPIO 34.

const int potPin = 34;

In the setup(), initialize a serial communication at a baud rate of 115200.

Serial.begin(115200);

In the loop(), use the analogRead()function to read the analog input from
the potPin.

potValue = analogRead(potPin);
Embedded Systems Laboratory 6
Experiment 4

Finally, print the values read from the potentiometer in the serial monitor.

Serial.println(potValue);
Upload the code provided to your ESP32. Make sure you have the right board
and COM port selected in the Tools menu.

Testing the Example

After uploading the code and pressing the ESP32 reset button, open the
Serial Monitor at a baud rate of 115200. Rotate the potentiometer and see the
values changing.

The maximum value you’ll get is 4095 and the minimum value is 0.

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