Arduino MAG3110 magnetometer example

Freescale’s MAG3110 is a small, low-power, digital 3-axis magnetometer. The device can be used in conjunction with a 3-axis accelerometer to realize an orientation independent electronic compass that can provide accurate heading information. It features a standard I2C serial interface output and smart embedded functions.

The MAG3110 is capable of measuring magnetic fields with an output data rate (ODR) up to 80 Hz; these output data rates correspond to sample intervals from 12.5 ms to several seconds. The MAG3110 is available in a plastic DFN package and it is guaranteed to operate over the extended temperature range of -40°C to +85°C.

Again for ease to use its easier to buy a module with the device fitted to it, here is one that I purchased. You can see the MAG3110 in the middle of the picture

I also found this schematic online of a similar module to the one pictured above. Looking at the schematic it looks very similar to the module

Connection

Layout

An I2C device so easy to wire up as per the connections above

Code

This particular code example does not require any libraries

[codesyntax lang=”cpp”]

#include <Wire.h>

#define MAG_ADDR  0x0E //7-bit address for the MAG3110, doesn't change

void setup()
{
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial for output
  config();            // turn the MAG3110 on
}

void loop()
{
  print_values();
  delay(5);
}

void config(void)
{
  Wire.beginTransmission(MAG_ADDR); // transmit to device 0x0E
  Wire.write(0x11);             // cntrl register2
  Wire.write(0x80);             // write 0x80, enable auto resets
  Wire.endTransmission();       // stop transmitting
  delay(15); 
  Wire.beginTransmission(MAG_ADDR); // transmit to device 0x0E
  Wire.write(0x10);             // cntrl register1
  Wire.write(1);                // write 0x01, active mode
  Wire.endTransmission();       // stop transmitting
}

void print_values(void)
{
  Serial.print("x=");
  Serial.print(read_x());
  Serial.print(",");  
  Serial.print("y=");    
  Serial.print(read_y());
  Serial.print(",");       
  Serial.print("z=");    
  Serial.println(read_z());
}

int mag_read_register(int reg)
{
  int reg_val;
  
  Wire.beginTransmission(MAG_ADDR); // transmit to device 0x0E
  Wire.write(reg);              // x MSB reg
  Wire.endTransmission();       // stop transmitting
  delayMicroseconds(2); //needs at least 1.3us free time between start and stop
  
  Wire.requestFrom(MAG_ADDR, 1); // request 1 byte
  while(Wire.available())    // slave may write less than requested
  { 
    reg_val = Wire.read(); // read the byte
  }
  
  return reg_val;
}

int mag_read_value(int msb_reg, int lsb_reg)
{
  int val_low, val_high;  //define the MSB and LSB
  val_high = mag_read_register(msb_reg);
  delayMicroseconds(2); //needs at least 1.3us free time between start and stop
  val_low = mag_read_register(lsb_reg);
  int out = (val_low|(val_high << 8)); //concatenate the MSB and LSB
  return out;
}

int read_x(void)
{
  return mag_read_value(0x01, 0x02);
}

int read_y(void)
{
  return mag_read_value(0x03, 0x04);
}

int read_z(void)
{
  return mag_read_value(0x05, 0x06);
}

[/codesyntax]

Testing

Open up the serial monitor

x=44,y=1138,z=1505
x=65175,y=580,z=2037
x=65117,y=745,z=1435
x=65145,y=1487,z=1814
x=64700,y=949,z=1912
x=64848,y=671,z=1921
x=65411,y=803,z=2218
x=64852,y=720,z=1644

Link
MAG3110 compass module three-axis electronic compass module magnetoresistive sensor magnetometer module