The file that is currently on an Arduino Mega 2560 or Mega ADK with a serial number of 85235333135351C09291

slimmed_ecompass_code_sep_18_2.ino

// This code reads a signal from the HNC6352 in degrees and writes it to a SD card. It uses LED flashes to report success to writing and errors

//Necessary libraries
#include <Wire.h>
#include <SD.h>

// Setup the Compass I2C address
int HMC6352SlaveAddress = 0x42;
int HMC6352ReadAddress = 0x41; //"A" in hex, A command is:
int headingValue;

// Set the CS pin for the on the Ethernet Shield, CS is pin 4.
const int chipSelect = 4;

// Define the LED driving pin
int led_13 = 13;

void setup(){

// "The Wire library uses 7 bit addresses throughout.
//If you have a datasheet or sample code that uses 8 bit address,
//you'll want to drop the low bit (i.e. shift the value one bit to the right),
//yielding an address between 0 and 127."

HMC6352SlaveAddress = HMC6352SlaveAddress >> 1; // I know 0x42 is less than 127, but this is still required

// Test the SD card
if (!SD.begin(chipSelect)) {
    digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(100);                // wait for a tenth of a second
    digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
    delay(100);               // wait for a tenth of a second
    digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(100);                // wait for a tenth of a second
    digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
    delay(100);               // wait for a tenth of a second
    digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(100);                // wait for a tenth of a second
    digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
    delay(100);               // wait for a tenth of a second
    digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(100);                // wait for a tenth of a second
    digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
    delay(100);               // wait for a tenth of a second
    digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(100);                // wait for a tenth of a second
    digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
    delay(100);               // wait for a tenth of a second
    return;
  }

Wire.begin();

// initialize the digital pin as an output.
pinMode(led_13, OUTPUT);

}

// Set the inital counter value
int number = 0;

//Begin the main loop
void loop(){

//"Get Data. Compensate and Calculate New Heading"
Wire.beginTransmission(HMC6352SlaveAddress);
Wire.write(HMC6352ReadAddress);              // The "Get Data" command
Wire.endTransmission();

//time delays required by HMC6352 upon receipt of the command
//Get Data. Compensate and Calculate New Heading : 6ms
delay(6);

Wire.requestFrom(HMC6352SlaveAddress, 2); //get the two data bytes, MSB and LSB

//"The heading output data will be the value in tenths of degrees
//from zero to 3599 and provided in binary format over the two bytes."
byte MSB = Wire.read();
byte LSB = Wire.read();

int heading= (MSB << 8) + LSB; //(MSB / LSB sum)
//  float headingInt = headingSum / 10;

 Serial.print(heading);
 Serial.println(" degrees");

// make a string for assembling the data to log:
  String dataString = "";
  dataString += String(number);
  dataString += ",";
  dataString += String(heading);

// open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  File dataFile = SD.open("datalog.txt", FILE_WRITE);

  // if the file is available, write to it:
  if (dataFile) {
    dataFile.println(dataString);
    dataFile.close();
  }
  // if the file isn't open, pop up an error:
  else {
    digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(1000);                // wait for a tenth of a second
    digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
    delay(1000);               // wait for a tenth of a second
  }

number++; // add 1 to the counter

// Double flash pin 13

digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
delay(100);                // wait for a tenth of a second
digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
delay(100);               // wait for a tenth of a second
digitalWrite(led_13, HIGH);   // turn the LED on (HIGH is the voltage level)
delay(100);                // wait for a tenth of a second
digitalWrite(led_13, LOW);    // turn the LED off by making the voltage LOW
delay(700);
}