ESP32 ADC (Analog Inputs) – Arduino IDE
Learn how to use ESP32 analog input pins using Arduino IDE. Analog pins are used to read various voltage levels.
Table of Content
Working of ADC
ESP32 ADC
ESP32 has two 12-bit SAR (Successive Approximation Register) ADCs.
| Channel | No of Inputs | GPIOs |
| ADC1 | 8 | 32 to 39 |
| ADC2 | 10 | 0, 2, 4, 12 to 15, 25 to 27 |
The resolution of ADCs in ESP32 is 12 bits. That means total 4096 (2^12) levels of voltages between V– and V+ can be detected. In ESP32 V– and V+ are 0 V and 3.3 V respectively. In other words the resolution of ESP32 is 3.3V/4096 i.e. 0.806mV.
Note: Applying voltage more than 3.3 Volts can damage your development board.
analogRead()
In Arduino IDE, the voltage levels on the analog pin can be measured using the analogRead() function.
analogRead(GPIOPin);analogRead() function takes GPIOPin as an argument and returns an analog reading on the GPIOPin.
Reading Potentiometer Value
In this example, we will look into using ESP32 ADCs to read a potentiometer value.
Connect the potentiometer input pins to the 3.3V and GND pins on ESP32, and connect the potentiometer output pin to any analog pin on the dev board. We will use GPIO pin 34 on the ESP32.
Code
int analogPin = 34;
int value = 0;
void setup() {
Serial.begin(115200);
}
void loop() {
value = analogRead(analogPin);
Serial.print("Pot value: ");
Serial.println(value);
delay(100);
}Other functions
| analogRead(pin) | Read analog input from an ADC pin |
| analogReadMillivolts(pin) | Read analog input from an ADC pin and convert it to calibrated results in mV |
| analogReadResolution(bits) | Set ADC resolution (9-12 bits), default is 12-bits |
| analogSetAttenuation(attenuation) | Set attenuation for all pins/channelsADC_ATTEN_DB_0, ADC_ATTEN_DB_2_5, ADC_ATTEN_DB_6, ADC_ATTEN_DB_11 |
| analogSetPinAttenuation(pin, attenuation) | Set attenuation for specific all pin/channel |
| analogSetWidth(bits) | Set ADC resolution (9-12 bits), default is 12-bits |