Lockin

[matthuszagh]

Integrate PLL and integer math to lock-in functionality.

[jordens]

I would suggest you try to actually use the code in the processing ISR in main.rs. That should show whether these wrappers are actually convenient or whether the code would be much shorter and easier to understand if they were inlined.

The moving of the batch and timer constants here doesn't seem right. dsp should be standalone and should not dictate the application. Inlining the code may quickly make the TODO redundant.

[jordens]

Nice!

Once TimestampHandler is factored out into dsp (see below), let's move the remaining changes to main.rs into a new PR (e.g. lockin-bin). Then this dsp PR can land right now and we can use the lockin-bin as a trial for the multiple-bin refactoring.

[jordens]

Nice.