Hi everyone,
I have managed to get a project using a hmc5883l compass and a mma7361 accellerometer to work int he same sketch and print onto a lcd, the problem I am struggling on is how to tilt compensate the compass. There seems to be only an adxl345 accellerometer code on the internet to work with the hmc5883l compass.
Could anyone spare 5 mintues to help me out with the formula to tilt compensate the compass? I am also unsure if i only need to compensate a single axis i.e X or Y as Z i think measures the G force which I dont need, I may be wrong in thinking this and both the X and Y axis data will be needed.
Here is the code I am using: (many thanks for any replies)
#include <Wire.h>
#include <HMC5883L.h>
#include <AcceleroMMA7361.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 7, 5, 4, 3, 2);
AcceleroMMA7361 accelero;
int x;
int y;
int z;
// Store our compass as a variable.
HMC5883L compass;
// Record any errors that may occur in the compass.
int error = 0;
// Out setup routine, here we will configure the microcontroller and compass.
void setup()
{
// Initialize the serial port.
Serial.begin(9600);
accelero.begin(13, 12, 11, 10, A0, A1, A2);
accelero.setARefVoltage(5); //sets the AREF voltage to 3.3V
accelero.setSensitivity(LOW); //sets the sensitivity to +/-6G
accelero.calibrate();
lcd.begin(20, 4);
lcd.print("Degrees:");
lcd.setCursor(9, 4);
lcd.print("Tilt");
Serial.println("Starting the I2C interface.");
Wire.begin(); // Start the I2C interface.
Serial.println("Constructing new HMC5883L");
compass = HMC5883L(); // Construct a new HMC5883 compass.
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));
}
// 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)
// 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' W, 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 = 0.0314;
heading += declinationAngle;
// Correct for when signs are reversed.
if(heading < 0)
heading += 2*PI;
// Check for wrap due to addition of declination.
if(heading > 2PI)
heading -= 2PI;
// Convert radians to degrees for readability.
float headingDegrees = heading * 180/M_PI;
// Output the data via the serial port.
Output(raw, scaled, heading, headingDegrees);
// 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);
}
// 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);
Serial.print(" \tHeading:\t");
Serial.print(heading);
Serial.print(" Radians \t");
Serial.print(headingDegrees);
Serial.println(" Degrees \t");
lcd.setCursor(0, 1);
lcd.print(headingDegrees);
lcd.print((char)223);
{
x = accelero.getXAccel();
y = accelero.getYAccel();
z = accelero.getZAccel();
Serial.print("\nx: ");
Serial.print(x);
Serial.print(" \ty: ");
Serial.print(y);
Serial.print(" \tz: ");
Serial.print(z);
Serial.print("\tG*10^-2");
lcd.setCursor(7, 3);
lcd.print(x);
}
delay(250);
}