Stap 4: Code
De code is heel eenvoudig en alles wat het doet is leest het kompas lezingen en drukt het uit op een seriële monitor. Het kompas kalibreert voor een paar seconden bij het uitvoeren van de code maken zeker niet te draaien of verstoren van het kompas, terwijl dit gebeurt, en nadat het is voltooid zou je een mooie stroom van gegevens van de sensor.
<p>// Reference the I2C Library<br>#include <wire.h> // Reference the HMC5883L Compass Library #include <hmc5883l.h></hmc5883l.h></wire.h></p><p>// Store our compass as a variable. HMC5883L compass; // Record any errors that may occur in the compass. int error = 0;</p><p>// Out setup routine, here we will configure the microcontroller and compass. void setup() { // Initialize the serial port. Serial.begin(9600);</p><p> Serial.println("Starting the I2C interface."); Wire.begin(); // Start the I2C interface.</p><p> Serial.println("Constructing new HMC5883L"); Serial.println("Setting scale to +/- 1.3 Ga"); error = compass.setScale(1.3); // Set the scale of the compass. if(error != 0) // If there is an error, print it out. Serial.println(compass.getErrorText(error)); Serial.println("Setting measurement mode to continous."); error = compass.setMeasurementMode(MEASUREMENT_CONTINUOUS); // Set the measurement mode to Continuous if(error != 0) // If there is an error, print it out. Serial.println(compass.getErrorText(error)); }</p><p>// Our main program loop. void loop() { // Retrive the raw values from the compass (not scaled). MagnetometerRaw raw = compass.readRawAxis(); // Retrived the scaled values from the compass (scaled to the configured scale). MagnetometerScaled scaled = compass.readScaledAxis(); // Values are accessed like so: int MilliGauss_OnThe_XAxis = scaled.XAxis;// (or YAxis, or ZAxis)</p><p> // Calculate heading when the magnetometer is level, then correct for signs of axis. float heading = atan2(scaled.YAxis, scaled.XAxis); // Once you have your heading, you must then add your 'Declination Angle', which is the 'Error' of the magnetic field in your location. // Find yours here: http://www.magnetic-declination.com/ // Mine is: -2��37' which is -2.617 Degrees, or (which we need) -0.0456752665 radians, I will use -0.0457 // If you cannot find your Declination, comment out these two lines, your compass will be slightly off. float declinationAngle = -0.0457; heading += declinationAngle; // Correct for when signs are reversed. if(heading < 0) heading += 2*PI; // Check for wrap due to addition of declination. if(heading > 2*PI) heading -= 2*PI; // Convert radians to degrees for readability. float headingDegrees = heading * 180/M_PI; </p><p> // Output the data via the serial port. Output(raw, scaled, heading, headingDegrees);</p><p> // Normally we would delay the application by 66ms to allow the loop // to run at 15Hz (default bandwidth for the HMC5883L). // However since we have a long serial out (104ms at 9600) we will let // it run at its natural speed. delay(66);//of course it can be delayed longer. }</p><p>// Output the data down the serial port. void Output(MagnetometerRaw raw, MagnetometerScaled scaled, float heading, float headingDegrees) { Serial.print("Raw:\t"); Serial.print(raw.XAxis); Serial.print(" "); Serial.print(raw.YAxis); Serial.print(" "); Serial.print(raw.ZAxis); Serial.print(" \tScaled:\t"); Serial.print(scaled.XAxis); Serial.print(" "); Serial.print(scaled.YAxis); Serial.print(" "); Serial.print(scaled.ZAxis);</p><p> Serial.print(" \tHeading:\t"); Serial.print(heading); Serial.print(" Radians \t"); Serial.print(headingDegrees); Serial.println(" Degrees \t"); }</p>
