wrong read out accelerometer BMA280

Hi

For a research project, I am currently trying to read the acceleration data from the BMA280. This chip is used by silabs on there WSTK expansion board. At this moment I'm following a complete procedure to initialize the accelerometer.

1. Perform self test
   1. Check if difference from read out of +X en -X is bigger than 800mg (answer: check)
   2. Check if difference from read out of +Y en -Y is bigger than 800mg (answer: check)
   3. Check if difference from read out of +Z en -Z is bigger than 400mg (answer: check)
2. Soft reset the accelerometer
   1. wait 1,5 sec
3. Initialize the accelerometer to my preferences
4. Perform Fast compensation
   1. Clear offset register
   2. Set offset compensation to X: 0g, Y: 0g, Z:+1g, BW 1%
   3. X-axis calibration
   4. Y-axis calibration
   5. Z-axis calibration
   6. Read offset X              my answer: x = -31 mg
   7. Read offset Y              my answer:  y = -15 mg
   8. Read offset Z             my answer:  z = 0 mg
5. init done

The values afterwards are x=+-20mg, y=+-2mg en z=+- -19mg. I expected the values would be x=+-0g, y=+-0g en z=+- -1g when the chip is laying flat on my desk.

I convert the acceleration data in this way.

volatile float factor = 0.488; // 8000/2^14 mg/LSB
// X-Axis in 0x02-0x03
LSBx = BMA280_read_register(USART1, BMA280_ACCD_X_LSB);
LSBx = LSBx >> 2;
MSBx = BMA280_read_register(USART1, BMA280_ACCD_X_MSB);
tmpx = (uint16_t)((MSBx << 6) | LSBx);
acceleration[0] = (float) tmpx * factor;

Can somebody confirm me If this is correct? Or give me the correct init from the accelerometer?

Thank you in advance

Best Regards

Nick