File content as of revision 0:c92d21a4e8c2:

#include "mbed.h"
I2C i2c(PB_7, PB_6);
Serial pc(USBTX, USBRX, 9600);
const int addr_accel_gyro = 0xD0;
const int addr_compus = 0x18;


char cmd[2];
char data[1];
char adata[1];
char mxl[1], mxh[1], myl[1], myh[1], mzl[1], mzh[1] , st[1];
double mg_x, mg_y, mg_z, MX, MY, MZ;

int main() {
    pc.printf("Start detectiong magnetism\r\n");
    wait(1.0);
    i2c.frequency(100000);
    
    cmd[0]=0x6B;
    cmd[1]=0x00;
    i2c.write(addr_accel_gyro,cmd,2);
    cmd[0] = 0x37;
    cmd[1] = 0x02;
    i2c.write(addr_accel_gyro,cmd,2);
    
    //write address of compus
    adata[0] = 0x0A;
    adata[1] = 0x12;
    i2c.write(addr_compus,adata,2);
    i2c.stop();
    wait(1);
    
    while(1) {
        
        //=========== x ===========
        //read mxl
        adata[0] = 0x03;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,mxl,1);

        //read mxh
        adata[0] = 0x04;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,mxh,1);
        
        
        //=========== y ===========
        adata[0] = 0x05;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,myl,1);
        
        adata[0] = 0x06;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,myh,1);
        
        
        //=========== z ===========
        adata[0] = 0x07;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,mzl,1);
        
        adata[0] = 0x08;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,mzh,1);
        
        //status 
        adata[0] = 0x09;
        i2c.write(addr_compus,adata,1);
        i2c.read(addr_compus|0x01,st,1);
        
        
        
        mg_x = short((mxh[0]<<8)|(mxl[0]));
        mg_y = short((myh[0]<<8)|(myl[0]));
        mg_z = short((mzh[0]<<8)|(mzl[0]));
        MX = mg_x*0.15;
        MY = mg_y*0.15;
        MZ = mg_z*0.15;
        pc.printf("MX= %f,MY= %f,MZ= %f\r\n",MX,MY,MZ);

        wait(0.5);
        
    }
    
}