hmc5883l-arduino.c

/*
Arduino Nano V3
SDA ---> A4
SCL ---> A5
*/

//I2C lib
#include <Wire.h>

////////////////////////////////////
// address

#define hmc5883_addr_read  0x3d
#define hmc5883_addr_write 0x3c
#define hmc5883_addr_rw    0x1e

/////////////////////////////////////
// regs

#define hmc5883_reg_config_a 0
#define hmc5883_reg_config_b 1
#define hmc5883_reg_mode     2
#define hmc5883_reg_x_msb    3
#define hmc5883_reg_x_lsb    4
#define hmc5883_reg_z_msb    5
#define hmc5883_reg_z_lsb    6
#define hmc5883_reg_y_msb    7
#define hmc5883_reg_y_msb    8
#define hmc5883_reg_status   9
#define hmc5883_reg_id_a     10
#define hmc5883_reg_id_b     11
#define hmc5883_reg_id_c     12

///////////////////////////////////////
// reg configure A
#define hmc5883_avg_1 1<<5
#define hmc5883_avg_2 2<<5
#define hmc5883_avg_4 3<<5
#define hmc5883_avg_8 4<<5

#define hmc5883_hz_0_75 0<<2
#define hmc5883_hz_1_5  1<<2
#define hmc5883_hz_3    2<<2
#define hmc5883_hz_7_5  3<<2
#define hmc5883_hz_15   4<<2
#define hmc5883_hz_30   5<<2
#define hmc5883_hz_75   6<<2

#define hmc5883_ms_normal   0
#define hmc5883_ms_positive 1
#define hmc5883_ms_negative 2

///////////////////////////////////////
// reg configure B

#define hmc5883_gain_0_88 0<<4
#define hmc5883_gain_1_33 1<<4
#define hmc5883_gain_1_9  2<<4
#define hmc5883_gain_2_5  3<<4
#define hmc5883_gain_4    4<<4
#define hmc5883_gain_4_7  5<<4
#define hmc5883_gain_5_6  6<<4
#define hmc5883_gain_8_1  7<<4

////////////////////////////////////////
// reg configure mode

#define hmc5883_md_continuous 0 
#define hmc5883_md_single     1

/////////////////////////////////////////

void setup()
{
  //usart debug
  Serial.begin(115200);
  
  //i2c start
  Wire.begin();

  //configure hmc5883l
  
  Wire.beginTransmission(hmc5883_addr_rw); 
  Wire.write( hmc5883_reg_config_a ); 
  Wire.write( hmc5883_avg_8 | hmc5883_hz_15 | hmc5883_ms_normal); 
  Wire.endTransmission(  );

  Wire.beginTransmission(hmc5883_addr_rw); 
  Wire.write( hmc5883_reg_config_b ); 
  Wire.write( hmc5883_gain_5_6 ); 
  Wire.endTransmission();
  
  Wire.beginTransmission(hmc5883_addr_rw); 
  Wire.write( hmc5883_reg_mode );  
  Wire.write( hmc5883_md_continuous); 
  Wire.endTransmission();

}

//format buffer
char buf[100];

void loop()
{
  //point to first data register
  Wire.beginTransmission(hmc5883_addr_rw);
  Wire.write(hmc5883_reg_x_msb); 
  Wire.endTransmission();

  int rxmax=6;  
  int rxc = 0;
  int rxdata[6];
  
  Wire.requestFrom(hmc5883_addr_rw, rxmax);
  while(Wire.available() && rxc<rxmax)
  {
    rxdata[rxc]=Wire.read();
    rxc++;
  }

  uint16_t x,y,z; //triple axis data
    x = rxdata[1] | rxdata[0] <<8; 
    z = rxdata[3] | rxdata[2] <<8;  
    y = rxdata[5] | rxdata[4] <<8; 
  
  sprintf(buf,"(X)%02x%02x (Z)%02x%02x (Y)%02x%02x (array)",rxdata[0],rxdata[1],rxdata[2],rxdata[3],rxdata[4],rxdata[5],rxdata[6]);
  Serial.println(buf);
  sprintf(buf,"(X)%04x (Z)%04x (Y)%04x (value)",x,z,y);
  Serial.print(buf);

  ///////////////////////////////////////////////////////////  
  
  
  int status;
  Wire.beginTransmission(hmc5883_addr_rw);
  Wire.write(hmc5883_reg_status); 
  Wire.endTransmission();
  Wire.requestFrom(hmc5883_addr_rw, 1);
  status=Wire.read();
  sprintf(buf," status=%02x",status);
  Serial.print(buf);
  
  ///////////////////////////////////////////////
  int a,b,c;
  Wire.beginTransmission(hmc5883_addr_rw);
  Wire.write(hmc5883_reg_id_a); 
  Wire.endTransmission();
  Wire.requestFrom(hmc5883_addr_rw, 1);
  a=Wire.read();
  
  Wire.beginTransmission(hmc5883_addr_rw);
  Wire.write(hmc5883_reg_id_b); 
  Wire.endTransmission();
  Wire.requestFrom(hmc5883_addr_rw, 1);
  b=Wire.read();
  
  Wire.beginTransmission(hmc5883_addr_rw);
  Wire.write(hmc5883_reg_id_c); 
  Wire.endTransmission();
  Wire.requestFrom(hmc5883_addr_rw, 1);
  c=Wire.read();
  
  sprintf(buf," ID=%c%c%c ",a,b,c);
  Serial.print(buf);
  ///////////////////////////////////////////////

  float angle= atan2((float)y,(float)x) * (180 / 3.14159265) + 180; // angle in degrees
  Serial.print(" angle=");
  Serial.print((int) angle);
   
 Serial.print(" You are heading ");
    if((angle < 22.5) || (angle > 337.5 ))
        Serial.print("South");
    if((angle > 22.5) && (angle < 67.5 ))
        Serial.print("South-West");
    if((angle > 67.5) && (angle < 112.5 ))
        Serial.print("West");
    if((angle > 112.5) && (angle < 157.5 ))
        Serial.print("North-West");
    if((angle > 157.5) && (angle < 202.5 ))
        Serial.print("North");
    if((angle > 202.5) && (angle < 247.5 ))
        Serial.print("NorthEast");
    if((angle > 247.5) && (angle < 292.5 ))
        Serial.print("East");
    if((angle > 292.5) && (angle < 337.5 ))
        Serial.print("SouthEast"); 
  
 

  Serial.println("");
}