Hi,
Here is the TX from BASE showing 5x Joystick, Temp, pressure, QEIDEG plus a spare BIT DATA values. This is read and used by the REMOTE as CONTROL.
The first reading is the UD, Up/Down and combined with the pressure, 'say' [ALT_UD] and [ALT_REM] will be the same at ground level. As UD is moved UP or DOWN then the ALT_UD will be a lower or higher number (lower pressure = Higher) than ALT_REM, so the prop motor should go faster or slower to match the 2x readings..
Next is dividing the UD reading! The range is somewhere between 250 and 850 and at rest approx 550. This has to be combined somehow with the pressure reading, to make the ALT_UD.
C