• Adafruit ADS1X15 or equivalent ADS1115 driver
• OneWire
• DallasTemperature

• I2C address: 0x48
• pH channel: differential A0-A1
• ORP channel: differential A2-A3
• Data rate: low/medium for stable readings
• Gain: choose a range that supports the expected signal
  • pH expected differential: about ±414mV
  • ORP expected differential: about ±1000mV

Cpp
#include <Wire.h>
#include <Adafruit_ADS1X15.h>
#include <OneWire.h>
#include <DallasTemperature.h>

// Set these to the actual ESP32 pins used with J2.
static const int PIN_I2C_SDA = 8;
static const int PIN_I2C_SCL = 9;
static const int PIN_ONEWIRE_DQ = 10;

Adafruit_ADS1115 ads;
OneWire oneWire(PIN_ONEWIRE_DQ);
DallasTemperature ds18b20(&oneWire);

float readAdsDiffMv(uint8_t mux) {
  int16_t raw = 0;
  if (mux == 0) raw = ads.readADC_Differential_0_1(); // pH
  else raw = ads.readADC_Differential_2_3();           // ORP

  // Adjust multiplier to match selected ADS1115 gain.
  // For GAIN_ONE on Adafruit ADS1X15, scale is commonly 0.125 mV/bit.
  return raw * 0.125f;
}

float filteredAdsMv(uint8_t mux) {
  const int N = 15;
  float sum = 0;
  for (int i = 0; i < N; i++) {
    sum += readAdsDiffMv(mux);
    delay(20);
  }
  return sum / N;
}

void setup() {
  Serial.begin(115200);
  Wire.begin(PIN_I2C_SDA, PIN_I2C_SCL);
  ds18b20.begin();

  if (!ads.begin(0x48)) {
    Serial.println("ADS1115 not found at 0x48");
    while (true) delay(1000);
  }

  ads.setGain(GAIN_ONE); // confirm range/noise tradeoff for ORP
  ads.setDataRate(RATE_ADS1115_128SPS);
}

void loop() {
  ds18b20.requestTemperatures();
  float tempC = ds18b20.getTempCByIndex(0);

  float phMv = filteredAdsMv(0);
  float orpMv = filteredAdsMv(1);

  // TODO: replace with calibrated conversion.
  float ph = phMv;   // placeholder
  float orp = orpMv; // mV before calibration offset

  Serial.printf("T=%.2f C, pH_raw=%.3f mV, ORP_raw=%.3f mV\n", tempC, phMv, orpMv);
  delay(1000);
}

• pH requires calibration with known buffer solutions.
• Store pH zero/offset and slope.
• Apply temperature compensation using DS18B20.
• ORP can be stored directly as differential mV plus calibration offset.

• pH range ±414mV remains within ADC input rails.
• ORP range ±1000mV remains within ADC input rails.
• Analog bandwidth is ~481.8Hz, so firmware should prioritize stable low-rate measurement rather than high-speed sampling.
• The filtered 3.3V rail attenuates high-frequency ESP32 noise; differential reads reject most common-mode rail movement.