ADC filters in Open...
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ADC filters in OpenTX transmitters - ON or OFF ?

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Trusted Member Customer
Joined: 3 years ago
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It came to my atention that drone FC manuals advise to turn off ADC filters in transmitters, cause FCs do input signal filtering by their own. They claim that by doing so the pilot achieves more direct feel without additional latency caused by double signal filtering (in the transmitter and then again in the FC)

Does it also apply to Brain controllers?

The ADC is filtering small gimbal positioning noises caused by crosstalk in the Transmitter itself.

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Joined: 5 years ago
Posts: 1001

Transmitter "OpenTX" is too general.
There are many brands of transmitters that use OpenTX as their operating system, and each brand has different models of transmitters. In addition to this, there are optional accessories that allow you to change the sticks of many of the different transmitters on the market.
ADC filters basically serve to filter out the "noise" that can be introduced and generated in the stick potentiometers. Depending on the model, the quality of the potentiometers can change considerably. In addition to this, the wear and aging of the potentiometers also matters, and whether they are watertight or not can be affected by the environment in which they are used (dust, sand, soil, humidity, etc. etc.).
There are also sticks that do not make use of classic potentiometers (resistive layer on which a slider slides) but more sophisticated systems that do not suffer from these problems (e.g., hall effect potentiometers).
For all these reasons, it is essential to ask the manufacturer of your transmitter for the information you need, specifying the model and any options/accessories fitted.
Usually each manufacturer sets the operating system with the most correct default values for their transmitters. It is therefore advisable to always use the factory/default settings.

On the other hand, as far as our control units are concerned, the signals received and processed together with the gyro signals for elevator, aileron and tail controls are "filtered" by PID filters. On the other hand, as for the collective pitch and throttle signals, they are not filtered but the signal that comes out is exactly what goes in (unless governor is used for throttle or rescue for collective pitch.
Our controllers unlike many others have the DIAGNOSTIC section by which you can also record all the input signals received from the receiver used and the output signals and then show the graphs. It is then possible after disabling the ADC filters on the transmitter to check whether the input signal curves are very "noisy" or not. Based on this analysis (in addition to the transmitter manufacturer's answers) you can evaluate whether you need to use ADC filters in the transmitter or not.

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