The frequent usage of the OpenTX Companion is trim the gimbal central value.
For example, You find the center value of the gimbal on the roll axis is 1525 in the Betaflight Configuration.
The central value of the gimbal in the range of 1500+-5 is normal.
1. Click the Edit Radio Settings in the dialog above. In the pop new dialog, choose the Calibration tab. As shown below.
2. Calculate the calibrated Mid Value according to the equation below.
Calibrated Mid Value = Original Mid Value + ( Betaflight Configuration Mid Value - 1500) * 2
Calibrated Mid Value = 1010 + (1525 - 1500)*2 = 1060
3. Update the Ail (Roll) Mid Value to 1060 and click the Write Models. button at the end of the tab.
The table above is just for Model 1 (right-hand throttle). So if you have a Mode 2 radio transmitter (left-hand throttle), if you want to calibrate the pitch value, you must change the Mid Value in the Throttle row.
4. Now back to the Betaflight Configuration, confirm if the gimbal calibration works.