AP_Compass: fixed calibration of 5883L compass

this fixes a compass initialisation bug where if the first value from
the compass isn't in the right range we would set bad calibration
scaling factors.

This also changes the maximum acceptable calibration values to 2000,
which is needed for the 5883 compass

pair-programmed-with: Randy Mackay

git-svn-id: https://arducopter.googlecode.com/svn/trunk@2718 f9c3cf11-9bcb-44bc-f272-b75c42450872

libraries/AP_Compass/AP_Compass_HMC5843.cpp

@@ -51,11 +51,6 @@ AP_Compass_HMC5843::init()
   }else
       product_id = AP_COMPASS_TYPE_HMC5843;
   
-  // calibration initialisation
-  calibration[0] = 1.0;
-  calibration[1] = 1.0;
-  calibration[2] = 1.0;
-
   while( success == 0 && numAttempts < 5 )
   {
       // record number of attempts at initialisation
@@ -82,12 +77,17 @@ AP_Compass_HMC5843::init()
 	  Wire.endTransmission();
 	  delay(10);
 
+	  // calibration initialisation
+	  calibration[0] = 1.0;
+	  calibration[1] = 1.0;
+	  calibration[2] = 1.0;
+
 	  // read values from the compass
 	  read();
 	  delay(10);
 
 	  // calibrate
-	  if( abs(mag_x) > 500 && abs(mag_x) < 1000 && abs(mag_y) > 500 && abs(mag_y) < 1000 && abs(mag_z) > 500 && abs(mag_z) < 1000)
+	  if( abs(mag_x) > 500 && abs(mag_x) < 2000 && abs(mag_y) > 500 && abs(mag_y) < 2000 && abs(mag_z) > 500 && abs(mag_z) < 2000)
 	  {
 		  calibration[0] = fabs(715.0 / mag_x);
 		  calibration[1] = fabs(715.0 / mag_y);
@@ -194,4 +194,4 @@ AP_Compass_HMC5843::write_register(int address, byte value)
   Wire.send(value);
   Wire.endTransmission();
   delay(10);
-}
+}