I'm revisiting a project of mine, the PCBs are done already - so i'm limited to software only.
I'm filtering the output of some accelerometers with a simple first order RC filter, with my cut off frequency at 100Hz, and being first order I've only got 20dB/decade of gain in the stopband. The ADC sampling frequency is 600Hz, so no aliasing issues there.
However, I'd like really to have more like 40dB/decade, therefore adding a software 1st order low pass filter will give me total 40dB/decade of roll off.
I don't want to move my -3dB point to less than 100Hz.
EDIT - I'm using this tool (http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html) but when I test it in Excel with some generic data, it doesn't filter per se - just reduces the amplitude, even if the input is within the passband. Clearly something fundamental I'm missing.
Additionally, the above clearly uses floating point math - whereas I'd like to stay integer... there must be a way to do this.