hmc5883l-pi/src/hmc5883l-pi.js

Module to read from the HMC5883L Magnetometer

var HMC5883L_REG_CONFIG_A = 0x00;
var HMC5883L_REG_CONFIG_B = 0x01;

var HMC5883L_REG_MODE =   0x02;
var HMC5883L_REG_MSB_X =  0x03;
var HMC5883L_REG_LSB_X =  0x04;
var HMC5883L_REG_MSB_Z =  0x05;
var HMC5883L_REG_LSB_Z =  0x06;
var HMC5883L_REG_MSB_Y =  0x07;
var HMC5883L_REG_LSB_Y =  0x08;
var HMC5883L_REG_STATUS = 0x09;
var HMC5883L_REG_ID_A =   0x0a;
var HMC5883L_REG_ID_B =   0x0b;
var HMC5883L_REG_ID_C =   0x0c;

var HMC5883L_MODE_CONTINUOUS = 0x00;
var HMC5883L_MODE_SINGLE     = 0x01;

var HMC5883L_ADDRESS = 0x1e;

var wpi = require('wiring-pi');
wpi.setup('wpi');
var fd = wpi.wiringPiI2CSetup(HMC5883L_ADDRESS);
wpi.wiringPiI2CWriteReg8(fd, HMC5883L_REG_MODE, HMC5883L_MODE_CONTINUOUS);

function toShort(value) {
  if ((value & (1<<15)) == 0) {
    return value;
  }
  return (value & ~(1<<15)) - (1<<15);
}

exports.readMag = function() {
  var msb = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_MSB_X);
  var lsb = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_LSB_X);
  var x = toShort(msb << 8 | lsb);

  msb = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_MSB_Y);
  lsb = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_LSB_Y);
  var y = toShort(msb << 8 | lsb);

  msb = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_MSB_Z);
  lsb = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_LSB_Z);
  var z = toShort(msb << 8 | lsb);
  return {x: x, y: y, z: z};
};

exports.readConfig = function() {
  var ret = {};
  var regValue = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_CONFIG_A);
  ret.averagedSamples = (regValue & 0x60) >> 5;
  ret.dataOutput = (regValue & 0x1c) >> 2;
  ret.measurementConfig = (regValue & 0x03);
  
  var regValue = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_CONFIG_B);
  ret.gain = (regValue & 0xe0) >> 5;

  var regValue = wpi.wiringPiI2CReadReg8(fd, HMC5883L_REG_MODE);
  ret.highSpeed = (regValue & 0x80 != 0);
  ret.operatingMode = (regValue & 0x03);
  
  return ret;
};

exports.dumpConfig = function() {
  var value = exports.readConfig();
  var averagedSampled;
  var dataOutput;
  var measurementConfig;
  var gain;
  
  switch(value.averagedSamples) {
  case 0:
    averagedSampled = 1;
    break;
  case 1:
    averagedSampled = 2;
    break;    
  case 2:
    averagedSampled = 4;
    break;    
  case 3:
    averagedSampled = 8;
    break;    
  }

  switch(value.dataOutput) {
  case 0:
    dataOutput = 0.75;
    break;
  case 1:
    dataOutput = 1.5;
    break;
  case 2:
    dataOutput = 3.0;
    break;
  case 3:
    dataOutput = 7.5;
    break;
  case 4:
    dataOutput = 15.0;
    break;
  case 5:
    dataOutput = 30.0
    break;
  case 6:
    dataOutput = 75.0;
    break;
  case 7:
    dataOutput = -1;
    break;
  }
  
  switch(value.measurementConfig) {
  case 0:
    measurementConfig = "Normal";
    break;
  case 1:
    measurementConfig = "Positive bias";
    break;
  case 2:
    measurementConfig = "Negative bias";
    break;
  case 3:
    measurementConfig = "!!reserved!!";
    break;
  }
  
  switch(value.gain) {
  case 0:
    gain = 1370;
    break;
  case 1:
    gain = 1090;
    break;
  case 2:
    gain = 820;
    break;
  case 3:
    gain = 660;
    break;
  case 4:
    gain = 440;
    break;
  case 5:
    gain = 390;
    break;
  case 6:
    gain = 330;
    break;
  case 7:
    gain = 230;
    break;
  }

  console.log("averagedSampled=%s, dataOutput=%s, measurementConfig=%s, gain=%s", averagedSampled, dataOutput, measurementConfig, gain);
};