Arduino code for reading OPT3001 sensor values

opt3001_test.c

//
// Arduino test code to read OPT3001 sensor values
// https://www.ti.com/product/OPT3001
// https://www.ti.com/lit/gpn/opt3001  (datasheet)
//

#include <Wire.h>

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Wire.begin();

  // configure
  Wire.beginTransmission(0x44); // ADDR pulled to GND
  Wire.write(0x01); // config register
  Wire.write(0xCE); // range, etc
  Wire.write(0x10);
  Wire.endTransmission();

  // partial write to change the read address
  Wire.beginTransmission(0x44);
  Wire.write(0);  // result register
  Wire.endTransmission(); // sends a STOP
}

void loop() {
  Wire.requestFrom(0x44, 2);  // read 2 bytes from last address
  
  uint8_t buf[4];
  uint16_t value;
  
  while (Wire.available()) {
    Wire.readBytes(buf, 2);
    uint8_t exp = buf[0] >> 4;
    value = buf[1] | ((buf[0] & 0x0F) << 8);

    Serial.print(exp);  // exponent (multiplier)
    Serial.print(' ');
    Serial.print(value);  // fractional value
    Serial.print('\n');

    // some delay here, since conversion is 800ms cycle
    delay(500);
  }
}