#include <Wire.h>

#define PRESSURE_SENSOR_ADDR 0x50   // Default device address

// Unit codes
#define UNIT_KPA 0x00
#define UNIT_BAR 0x01
#define UNIT_PSI 0x02
#define UNIT_ATM 0x03


// Write a register value
void writeRegister(uint8_t reg, uint8_t value) {
  Wire.beginTransmission(PRESSURE_SENSOR_ADDR);
  Wire.write(reg);
  Wire.write(value);
  Wire.endTransmission();
}


// Read one byte from register
uint8_t readRegister(uint8_t reg) {
  Wire.beginTransmission(PRESSURE_SENSOR_ADDR);
  Wire.write(reg);
  Wire.endTransmission(false);  // repeated start

  Wire.requestFrom(PRESSURE_SENSOR_ADDR, (uint8_t)1);
  if (Wire.available()) {
    return Wire.read();
  }
  return 0xFF;
}


// Read 16-bit pressure value
// Returns scaled fixed-point value (divide by 100.0)
uint16_t readPressureRaw16() {
  Wire.beginTransmission(PRESSURE_SENSOR_ADDR);
  Wire.write(0x00);             // pressure high byte register
  Wire.endTransmission(false);  // repeated start

  Wire.requestFrom(PRESSURE_SENSOR_ADDR, (uint8_t)2);

  uint8_t highByte = 0;
  uint8_t lowByte  = 0;

  if (Wire.available()) highByte = Wire.read();
  if (Wire.available()) lowByte  = Wire.read();

  return ((uint16_t)highByte << 8) | lowByte;
}


// Convert fixed-point to float
float readPressureValue() {
  uint16_t raw = readPressureRaw16();
  return raw / 100.0;
}


// Set output unit
void setUnit(uint8_t unitCode) {
  writeRegister(0x02, unitCode);
}


// Read current unit register
uint8_t getUnit() {
  return readRegister(0x02);
}


// Print unit text
const char* unitToString(uint8_t unitCode) {
  switch (unitCode) {
    case UNIT_KPA: return "kPa";
    case UNIT_BAR: return "bar";
    case UNIT_PSI: return "psi";
    case UNIT_ATM: return "atm";
    default:       return "unknown";
  }
}

void setup() {
  Serial.begin(9600);
  Wire.begin();

  // Default unit
  uint8_t currentUnit = getUnit();
  Serial.print("Default Unit: ");
  Serial.println(unitToString(currentUnit));

  Serial.println();
  Serial.println("Cycling through all units...");
  Serial.println();

  // Test all supported units once
  uint8_t testUnits[] = { UNIT_KPA, UNIT_BAR, UNIT_PSI, UNIT_ATM };

  for (uint8_t i = 0; i < 4; i++) {
    setUnit(testUnits[i]);
    delay(100);

    float pressure = readPressureValue();
    uint8_t confirmUnit = getUnit();

    Serial.print("Unit set to: ");
    Serial.print(unitToString(confirmUnit));
    Serial.print(" | Pressure = ");
    Serial.print(pressure, 2);
    Serial.print(" ");
    Serial.println(unitToString(confirmUnit));

    delay(1000);
  }

  // Return to kPa for live monitoring
  setUnit(UNIT_KPA);
  delay(100);

  Serial.println();
  Serial.println("Live pressure monitoring in kPa...");
  Serial.println("----------------------------------------");
}

void loop() {
  float pressure = readPressureValue();
  uint8_t currentUnit = getUnit();

  Serial.print("Pressure: ");
  Serial.print(pressure, 2);
  Serial.print(" ");
  Serial.println(unitToString(currentUnit));

  delay(1000);
}