HMC6352 not accurate

Hello everyone,

I have been battling with the programing of the compass HMC6352 to get accurate reading but so far all what I have done has not work…
Well I am using arduino UNO atmega328P. see below the code I used.
while I upload the code, I have readings but the problem comes when I rotate the compass 90degrees. the resulting indication on the serial monitor does not reflect the same 90degrees. I would like to calibrate and I wrote the code for calibration with which I tested the compass once more. but no change.

can anyone lead me or provide me with the calibration code… or anything that will help me move forward…

thank you

#include <Wire.h>
#include <LiquidCrystal.h>

//LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // initialize the numbers of the interface pins

int compass_address = 0x42; // initialization of the address of the compass
int slave_address, i, current_value, heading_value; // declaration of variables
byte heading_data[2]; // declaration of heading_data as array

void setup()
{

slave_address = compass_address >> 1; // this shift the bit right one position results in 0x21 as the address to pass to TWI
Serial.begin(9600); // determine the speed of data transmission
// set up
CLKPR = (1<<CLKPCE);
CLKPR = 0;
Wire.begin();
// lcd.begin(16, 4); // set the LCD’s number of columns and rows
// lcd.setCursor(0, 0); // set the cursor to column 0 and line 1
// lcd.print(“Robot heading”); // Print a message to the LCD
}

void loop()
{
Wire.beginTransmission(slave_address); // start of data transmission
Wire.send(“A”); // get current data
Wire.endTransmission(); // end of data transmission
delay(100); // delay of 1s before refreshing the data

Wire.requestFrom(slave_address, 2); // request the 2 bytes heading of 8 bits each
i = 0;
while(Wire.available() && i < 2)
{
heading_data = Wire.receive();
i++;
}
heading_value = (heading_data[0]*256 + heading_data[1]); // add the first byte (MSB) and second byte (LSB)

current_value = heading_value/10;
// lcd.setCursor(0, 1);
Serial.print(current_value);
Serial.print(".");
Serial.print(heading_value %10);
// Serial.setCursor(7, 1);
Serial.print(“degrees\n”);
delay(100); // only 70 microseconds are necessary
}

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