The answer to your question depends on the target device you are thinking of: PSoC1, PSoC3 or 5, you are here in the "pure" software-forum.
PSOC 1, filters are switch cap, you can modify filter parameters with register writes. However
the filter response is not a simple write to a single register. You would build an array of
values for all the caps and clocks, for a given response, and use that to control config thru
register writes. Designer wizard could be used to get values for each desired response.
PSOC 3/5 different matter. Depends on use of IIR or FIR how you would approach. Right
now not well documented how to do this. But you can access coefficients of filter to alter
response. Or use the DFB assembler http://www.cypress.com/?rID=60720 and build from
the ground up. Note Creator wizard gives you coefficient values to use.
PSOC 4 has no DMA or DFB, but does have a 32 x 32 multiplier, so if sample rate of filter
not to high simple FIR or IIR coding for a filter could be done.
In closing the DSP approach in PSOC 3/5 probably easier to tune than PSOC 1, but all could
work depending on your goals.
Thank you for your assistance.
Bob Marlowe, I'm using PSoc 5.
danaaknight, I'll use an FIR filter. The DFB assembler you're suggesting seems interesting, although it looks like a lot of effort for a relatively simple task as this.