ARM Learning

#include "Wire.h"
#define TMP102_I2C_ADDRESS 72 /* This is the I2C address for our chip. This value is correct if you tie the ADD0 pin to ground. See the datasheet for some other values. */
 
 
void setup() 
{
  Wire.begin(); // start the I2C library
  Serial.begin(115200); //Start serial communication at 115200 baud
}
 
 
void loop() 
{
  getTemp102();
  delay(5000); //wait 5 seconds before printing our next set of readings. 
}
 
void getTemp102()
{
  byte firstbyte, secondbyte; //these are the bytes we read from the TMP102 temperature registers
  int val; /* an int is capable of storing two bytes, this is where we "chuck" the two bytes together. */ 
  float convertedtemp; /* We then need to multiply our two bytes by a scaling factor, mentioned in the datasheet. */ 
  float correctedtemp; 
 
  /* Reset the register pointer (by default it is ready to read temperatures)
You can alter it to a writeable register and alter some of the configuration - 
the sensor is capable of alerting you if the temperature is above or below a specified threshold. */
 
  Wire.beginTransmission(TMP102_I2C_ADDRESS); //Say hi to the sensor. 
  Wire.write(0x00);
  Wire.endTransmission();
  Wire.requestFrom(TMP102_I2C_ADDRESS, 2);
  Wire.endTransmission();
 
 
  firstbyte      = (Wire.read()); 
  /*read the TMP102 datasheet - here we read one byte from
   each of the temperature registers on the TMP102*/
  secondbyte     = (Wire.read()); 
  /*The first byte contains the most significant bits, and 
   the second the less significant */
    val = firstbyte;
    if ((firstbyte & 0x80) > 0) 
    {
      val |= 0x0F00;
    } 
    val <<= 4; 
 /* MSB */
    val |= (secondbyte >> 4);    
/* LSB is ORed into the second 4 bits of our byte.
Bitwise maths is a bit funky, but there's a good tutorial on the playground*/
    convertedtemp = val*0.0625;
    correctedtemp = convertedtemp - 5; 
    /* See the above note on overreading */
 
 
  Serial.print("firstbyte is ");
  Serial.print("\t");
  Serial.println(firstbyte, BIN);
  Serial.print("secondbyte is ");
  Serial.print("\t");
  Serial.println(secondbyte, BIN);
  Serial.print("Concatenated byte is ");
  Serial.print("\t");
  Serial.println(val, BIN);
  Serial.print("Converted temp is ");
  Serial.print("\t");
  Serial.println(val*0.0625);
  Serial.print("Corrected temp is ");
  Serial.print("\t");
  Serial.println(correctedtemp);
  Serial.println();
}