Convert Raw 14 bit Two's Complement to Signed 16 bit Integer

Question

I am doing some work in embedded C with an accelerometer that returns data as a 14 bit 2\'s complement number. I am storing this result directly into a uint16_t

Answer 1

I would do simple arithmetic instead. The result is 14-bit signed, which is represented as a number from 0 to 2^14 - 1. Test if the number is 2^13 or above (signifying a negative) and then subtract 2^14.

int16_t fxls8471qr1_convert_raw_accel_to_mag(uint16_t raw, enum fxls8471qr1_fs_range range) 
{
  int16_t raw_signed = raw;
  if(raw_signed >= 1 << 13) {
    raw_signed -= 1 << 14;
  }

  uint16_t divisor;
  if(range == FXLS8471QR1_FS_RANGE_2G) {
    divisor = FS_DIV_2G;
  }
  else if(range == FXLS8471QR1_FS_RANGE_4G) {
    divisor = FS_DIV_4G;
  }
  else {
    divisor = FS_DIV_8G;
  }

  return ((int32_t)raw_signed * RAW_SCALE_FACTOR) / divisor;
}

Please check my arithmetic. (Do I have 13 and 14 correct?)