Enable arbitrary decimation of ADC data
To any power of two. Right now 8x decimation is not included, nor anything over 32x.
Here are some documents detailing the ADC decimation filters.
https://dcc.ligo.org/T1600066/
might have enough info to re-create the design of the filter.
https://dcc.ligo.org/T1500075/
also has some info.
We can either design the filter at model build, or assemble the filter from two equivalent filters, e.g. build an 8x filter from a 2x and 4x. It's not clear if the phase shift of combining filters is acceptable, but it's probably fine.