ESP32-S2 TFT Feather - analog to digital in Arduino

Question

I have a gas sensor that I am trying to read. I have connected the sensor to the analog input of ESP-S2 TFT Feather. When I change the analog to digital and read the measured voltage, the measured voltage is very very high. I figured out the resolution of this board is 13 bit. But, the measured voltage is still very high.

 int analogInPin = A2; 
 void readco() {
 // read the analog in value:
 sensorValue = 0;
 const int res = 8191; //resolution = 13-bit and 2^13 - 1 = 8191
 
  sensorValue = analogRead(analogInPin) + sensorValue;   
  iaq_data.co_0=(float) sensorValue*3.3/res;

If you are using Arduino-ESP32, the default ADC resolution is 12-bit except for ESP32S3. Read the doc to see how to set the analogReadResolution(). — hcheung
– hcheung, Commented Oct 25, 2022 at 1:02

Rohit Sardessai · Accepted Answer · 2022-10-25 07:34:10Z

0

From the ESP32-S2 docs found here,

Resolution of ESP32-S2 ADC raw results under Single Read mode is 12-bit

Are you sure your resolution is 13 bit?

Also, you seem to be adding sensorValue to itself every time. You initialise it to 0 every time so it should not matter but I would remove that.

This code should work:

int 12_bit_resolution = 4095; // 2^12 4096 - 1
input_voltage = analogRead(analogInPin) * (3.3 / 12_bit_resolution);

answered Oct 25, 2022 at 7:34

Rohit Sardessai

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