IoT 3.3V I2C Pressure sensor with ESP32 for Swimming Pool Controller

It looks like the provided code is written for HT66F0176, a Holtek microcontroller, not for Arduino/ESP32. For ESP32, you can try this:

#include <Wire.h>

#define I2C_ADDRESS 0x78  // 7-bit I2C address of the sensor
#define CMD_MEASURE 0xAC

void setup() {
  Serial.begin(115200);
  Wire.begin(); // SDA, SCL default to GPIO21, GPIO22 on ESP32
}

void loop() {
  if (triggerMeasurement()) {
    float pressure = 0, temperature = 0;
    if (readSensor(pressure, temperature)) {
      Serial.print("Pressure (Pa): ");
      Serial.print(pressure);
      Serial.print(" | Temperature (°C): ");
      Serial.println(temperature);
    } else {
      Serial.println("Failed to read sensor.");
    }
  } else {
    Serial.println("Measurement command failed.");
  }
  delay(1000); // Read every 1s
}

bool triggerMeasurement() {
  Wire.beginTransmission(I2C_ADDRESS);
  Wire.write(CMD_MEASURE);
  return Wire.endTransmission() == 0;
}

bool readSensor(float &pressure, float &temperature) {
  // Wait until sensor is ready
  uint8_t status = 0;
  for (int i = 0; i < 100; i++) {
    Wire.requestFrom(I2C_ADDRESS, 1);
    if (Wire.available()) {
      status = Wire.read();
      if (((status >> 5) & 0x01) == 0) break; // Not busy
    }
    delay(10);
  }

  // Read 6 bytes
  Wire.requestFrom(I2C_ADDRESS, 6);
  if (Wire.available() < 6) return false;

  uint8_t buffer[6];
  for (int i = 0; i < 6; i++) buffer[i] = Wire.read();

  // Pressure raw: 3 bytes
  uint32_t press_raw = ((uint32_t)buffer[0] << 16) |
                       ((uint32_t)buffer[1] << 8)  |
                       (uint32_t)buffer[2];

  // Temp raw: 2 bytes
  uint16_t temp_raw = ((uint16_t)buffer[3] << 8) |
                       (uint16_t)buffer[4];

  // Convert based on 0–1MPa calibration
  double CAL_L = -125000;
  double CAL_H = 1125000;
  pressure = ((double)press_raw / 16777216.0) * (CAL_H - CAL_L) + CAL_L;
  temperature = ((double)temp_raw / 65536.0) * 190.0 - 40.0;

  return true;
}

since you are using the ESP32 and working on IoT projects, here are some more ideas for you.

https://www.pcbway.com/blog/10/Making_IoT_projects_with_ESP32_____Innovation___Implementation_S2E6.html

@aliarifat Thanks for your time to help. I have loaded the code on the ESP32 and there was no errors - very good start. The results are less promising. The Sensor is design to measure water pressure up to 1 MPa. As a bonus, it also provide the temperature of the water. When I run the code with the sensor just at atmospheric pressure, I was expecting a value of close to zero for the pressure and around 26°C (My workshop temperature). The values I am getting is -105kPa for the pressure and the Temperature is jumping from -20°C to 130°C. I did a very crude test on the pressure. It is very stabile around -104 986 Pa. If I blow in the sensor ( I know sounds silly 🙂 , but then the pressure go to -104 942 Pa. So I think it is just the calibration factor/ correction issue. The temperature is a different story, not sure what the go there is.

Hi @aliarifat I had another look at the code yesterday. I have changed the following:

// Pressure raw: 3 bytes - Jaco change buffer[0] to buffer[1] and the same for the rest (0,1,2 to 1,2,3)
press_raw = (buffer[1] << 16) | (buffer[2] << 8) | buffer[3];

as well as :

// Temp raw: 2 bytes - Jaco change 3,4 to 4,5
temp_raw = (buffer[4] << 8) | buffer[5];

based on

 Is that correct, or am I missing something?

Regards

Jaco