Code with annotation:
/*
*
* Compass.ino - Example sketch for reading a heading from an HMC5883L triple axis magnetometer.
*
* GY-273 Compass Module -> Arduino
* VCC -> VCC (See Note Below)
* GND -> GND
* SCL -> A5/SCL, (Use Pin 21 on the Arduino Mega)
* SDA -> A4/SDA, (Use Pin 20 on the Arduino Mega)
* DRDY -> Not Connected (in this example)
*
* Voltage Note
* ~~~~~~~~~~~~
* The GY-273 Board has a 3v3 Regulator on it, and the SDA/SCL are pulled up to that so it is OK to
* use with 5v Arduino's.
*
* If you are using any other breakout, or the raw IC, you need to be using 3v3 to supply and signal!
*
* Datasheet: http://goo.gl/w1criV
*
* Copyright (C) 2014 James Sleeman
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* @author James Sleeman, http://sparks.gogo.co.nz/
* @license MIT License
*
*/
#include <Arduino.h>
#include <Wire.h>
#include <HMC5883L_Simple.h>
// Create a compass
HMC5883L_Simple Compass;
void setup()
{
Serial.begin(9600);
Wire.begin();
// Magnetic Declination is the correction applied according to your present location
// in order to get True North from Magnetic North, it varies from place to place.
//
// The declination for your area can be obtained from http://www.magnetic-declination.com/
// Take the "Magnetic Declination" line that it gives you in the information,
//
// Examples:
// Christchurch, 23° 35' EAST
// Wellington , 22° 14' EAST
// Dunedin , 25° 8' EAST
// Auckland , 19° 30' EAST
//
Compass.SetDeclination(23, 35, 'E');
// The device can operate in SINGLE (default) or CONTINUOUS mode
// SINGLE simply means that it takes a reading when you request one
// CONTINUOUS means that it is always taking readings
// for most purposes, SINGLE is what you want.
Compass.SetSamplingMode(COMPASS_SINGLE);
// The scale can be adjusted to one of several levels, you can probably leave it at the default.
// Essentially this controls how sensitive the device is.
// Options are 088, 130 (default), 190, 250, 400, 470, 560, 810
// Specify the option as COMPASS_SCALE_xxx
// Lower values are more sensitive, higher values are less sensitive.
// The default is probably just fine, it works for me. If it seems very noisy
// (jumping around), incrase the scale to a higher one.
Compass.SetScale(COMPASS_SCALE_088);
// The compass has 3 axes, but two of them must be close to parallel to the earth's surface to read it,
// (we do not compensate for tilt, that's a complicated thing) - just like a real compass has a floating
// needle you can imagine the digital compass does too.
//
// To allow you to mount the compass in different ways you can specify the orientation:
// COMPASS_HORIZONTAL_X_NORTH (default), the compass is oriented horizontally, top-side up. when pointing North the X silkscreen arrow will point North
// COMPASS_HORIZONTAL_Y_NORTH, top-side up, Y is the needle,when pointing North the Y silkscreen arrow will point North
// COMPASS_VERTICAL_X_EAST, vertically mounted (tall) looking at the top side, when facing North the X silkscreen arrow will point East
// COMPASS_VERTICAL_Y_WEST, vertically mounted (wide) looking at the top side, when facing North the Y silkscreen arrow will point West
Compass.SetOrientation(COMPASS_HORIZONTAL_X_NORTH);
}
// Our main program loop.
void loop()
{
float heading = Compass.GetHeadingDegrees();
Serial.print("Heading: \t");
Serial.println( heading );
delay(100);
}
