I am new to pixhawk. I am using pixhawk cube 2.1. I need to use pixhawk's own barometer to calculate the altitude. Please guide me that how to get readings of the barometer or the baro altitude. I am using PX4 firmware version 1.6.3. In the mavlink inspector (Qground controller), i have not seen any altitude thread. Do i need to use different firmware to get the pixhawk's built-in barometer working for the altitude or do i need to enable some parameter ?