File content as of revision 2:ae1bfb236387:

#include "mbed.h"
#include "LSM9DS1.h"
#include "IMU.h"

#define PI 3.1514

IMU::IMU() {

    LSM9DS1 I(p9, p10, 0xD6, 0x3C);
    I.begin();
    if (!I.begin()) {
        printf("Failed to communicate with LSM9DS1.\n");
    }
    I.calibrate(1);
    bool state;
    float ax01 = I.calcAccel(I.ax);
    float ay01 = I.calcAccel(I.ay);
    float az01 = I.calcAccel(I.az);
    float ax0 = ax01;
    float ay0 = ay01;
    float az0 = az01; 
    float ax;
    float ay;
    float az;
    float theta;
}
    
void IMU::trackBed()
{
    if (state != 0) {
        return;
    }
    else {
        while(state == 0) {
        
            while(!I.accelAvailable());
            I.readAccel();
        
             // current a = <ax,ay,az> 
            ax = I.calcAccel(I.ax);
            ay = I.calcAccel(I.ay);
            az = I.calcAccel(I.az);
            // theta in degrees between a0 and a
            theta = acos((ax0*ax + ay0*ay + az0*az)/(sqrt(ax0*ax0+ay0*ay0+az0*az0)*sqrt(ax*ax+ay*ay+az*az)))*180/PI;
        }
    }
}
        
void IMU::trackHeading()
{
    if (state != 1) {
        return;
    }
    else {
        while (state == 1) {
            
            while(!I.accelAvailable());
            
            I.readAccel();
            ax0 = I.calcAccel(I.ax);
            ay0 = I.calcAccel(I.ay);
            az0 = I.calcAccel(I.az);
        }
    }
}