LSM9DS1 A 9 degree of freedom Inertial Navigation Chip

Applying the Calibrations

There are 4 values to be applied to 3 axis, for each scale and for the magnetometer, accelerometer and the gyroscope sensors.

A data structure for the magnetometer calibration values

var magcal={
  scale4:{scale:4,table:[
  {offset:0,A:1,B:0,C:0},
  {offset:0,A:0,B:1,C:0},
  {offset:0,A:0,B:0,C:1}
  ]},
  scale8:{scale:4,table:[
  {offset:1060.85,A:0.98742,B:0.01417,C:-0­.0005998},
  {offset:24.469956,A:	0.124389675,B:0.996380859,C:-0.000561968­},
  {offset:561.2217795,A:0.020594208	,B:0.00552387,C:1}
  ]},
  scale12:{scale:4,table:[
  {offset:0,A:1,B:0,C:0},
  {offset:0,A:0,B:1,C:0},
  {offset:0,A:0,B:0,C:1}
  ]},
  scale16:{scale:4,table:[
  {offset:0,A:1,B:0,C:0},
  {offset:0,A:0,B:1,C:0},
  {offset:0,A:0,B:0,C:1}
  ]},
};

Code to apply the calibration values

function useCalibration(cal,autocalc,data){
 var i;var D=[0,0,0];var F=[0,0,0];
if(autocalc<1){
  for(i=0;i<3;i++)D[i]=data[i];
  return D;
}//endif
 for(i=0;i<3;i++)D[i]=data[i]-cal.table[i­].offset;
if(autocalc===1)return D;
for(i=0;i<3;i++){
  F[i]=D[0]*cal.table[i].A;
  F[i]+=D[1]*cal.table[i].B;
  F[i]+=D[2]*cal.table[i].C;
}//next i
for(i=0;i<3;i++)F[i]=F[i]*cal.scale/(1<<­15);
 return F;
}//end useCalibration

Applying the Use calibration function

function displayMag(){
var m;
if(W.Mread(W.MREGval.ZYXDA)){  //new data available
// console.log("Mag data available");
 m=W.mReadBytes(W.MagRegs.OUT_X_L_M, 6);
//autocalc  0=raw, 1=raw-offset, 2 Gauss  
  var autocalc=2;
M=useCalibration(magcal.scale8,autocalc,­m);
console.log(" "+M[0]+","+M[1]+","+M[2]); //raw
}//endif
}//end displayMag

Listing the scales

function showscales(){
for(var x in magcal)console.log(x);
}

An Output Sample

>
=undefined
AG replied 104
M replied 61
do a reset of AG
AG SWreset= 0
reset the magnetometer
scale4
scale8
scale12
scale16
 -0.00014387969,-0.09589182669,-0.2014648­1881
 0.00023358480,-0.09475134273,-0.20193948­954
 -0.00110189705,-0.09552740429,-0.2003836­0033
 0.00167522343,-0.09481362313,-0.19971340­522
 0.00177061744,-0.09662211209,-0.20106377­922
 0.00193627169,-0.09344444901,-0.20128787­409
 0.00032607760,-0.09668255780,-0.20133741­284
 0.00229249432,-0.09388396965,-0.20384650­603

1 Attachment

• Magtest1.js