Input devices

ADS1115 ADC with ESP32

Parallel RGB display boards rarely have analog pins left, and the ESP32 ADC is noisy and not linear. An ADS1115 solves both over two I2C wires: four single-ended inputs at 16 bits. If the connector on your board offers I2C and nothing else, this is how you read a pressure transducer or a thermistor.

Gain confuses people. The range settings run from ±6.144 V down to ±0.256 V, but gain changes only the scaling, not what the pins can take. On a 3.3 V supply, any input must stay below about VDD + 0.3 V, so the ±6.144 V range does not let you connect 5 V. A 0 to 5 V sensor still needs a divider. Pick the smallest range that covers your signal, because a wider one wastes resolution. For 0 to 3.3 V, ±4.096 V is the usual choice, giving 125 µV per step.

The ADDR pin sets the address: GND is 0x48, VDD 0x49, SDA 0x4A and SCL 0x4B. Up to four can share a bus, which gives 16 inputs. Run a scan first, and remember that 0x48 can collide with other parts. It is not fast, and the code below uses 128 samples per second. So it suits slow signals and not audio. Single-ended readings go from 0 upwards, and the sign bit is used only for differential ones. Differential inputs help when a small signal sits on a noisy ground. The sources here are guides, so check TI's datasheet for exact limits.

#include <Wire.h>

const int SDA_PIN = 8, SCL_PIN = 9;
const uint8_t ADDR = 0x48;

void setup() {
  Serial.begin(115200);
  Wire.begin(SDA_PIN, SCL_PIN);
}

void loop() {
  Wire.beginTransmission(ADDR);      // config: A0, +/-4.096 V, single shot, 128 SPS
  Wire.write(0x01); Wire.write(0xC3); Wire.write(0x83);
  Wire.endTransmission();
  delay(10);
  Wire.beginTransmission(ADDR);
  Wire.write(0x00);                  // conversion register
  Wire.endTransmission();
  Wire.requestFrom(ADDR, (uint8_t)2);
  int16_t raw = Wire.read() << 8;
  raw |= Wire.read();
  Serial.printf("A0 %.4f V\n", raw * 0.000125);
  delay(1000);
}

Use this information at your own risk. It is for general guidance only: the example code compiles, but it has not been tested on every part, and modules differ between sellers. Check the manufacturer's data before you build. Product names belong to their owners, and LCD Ultra Pro is not affiliated with them. See our Terms.