Add a low pass filter to common libraries

[Roozki]

We currently use 2 joysticks to control our arm (each with 3 potentiometers). They work well, but we are not really filtering or processing the data in any way. This is a bit worrisome, and we'd have better control filtering their signals.

In any case, having a ready-to-go filter to include in our firmware is desirable.

For the joysticks, we want a low-pass filter. Something that filters out big jumps in the data, but keeps the slower-changing inputs. For this a low-pass FIR filter is probably all we need.

There's a lot of low pass filters out there, but a single order FIR will work for the arm control panel joysticks. They cost a lot computation-wise, but effective.

What done looks like:

An FIR filter function, taking in a struct. (a class would work too, although just a function might be more compatible with arduino). Including test coverage (might be the hardest part, injecting data and detecting a smooth signal)

[douglasichen]

@Roozki

From my understanding, we want to apply a filter to the raw data coming from joysticks.

I don't see any code in FirmFlake for handling the raw data of joysticks. I only see armFirmware.cpp and armFirmware.ino, which is taking serialized inputs, which doesn't seem like raw data. What code is relevant for turning raw input into serialized input? (or just reading raw input in general - so i can get a feel of what that data looks like)

[Roozki]

@douglasichen
The common library should be agnostic to the data, any analog signal should be able to be filtered with this library. Try to aim for 32-bit signals. However the arm panel's signal range was from 0 - 1023 for each axis. We should be able to reuse this library (by just including a .h file) for any analog input we need. So any joystick, or potentiometer dial should be able to use this.

But wow I can't find the arm panel firmware either. Not sure where it is but I will try to find it soon. It may not be backed up in github which would be very disorganized...

It was a pretty simple app, and we may need to re-write it.