Hello Jeffrey,

May be all you need is math library. If all you want to remove from
signal is short peaks, exponential filter is enough. It has the
following transfer function
               1
       W(s)= ------
             Ts + 1
Calculation scheme is very simple.
Let us call x the result from ADC and filtered result.
Alpha is  ]0,1[ and determines time constant T. The bigger is alpha,
the smaller is T.
0) measurement ( x = ADC_result )
1) y = x
2) y_before = y
3) measurement ( x = ADC_result )
4) delta = x - y_before
5) y = y_before + alpha*delta ---> the next filtered number is ready
6) goto 3

So all you need is signed addition and multiplication. Be aware of
number of binary digits used to store y_before and to do all
calculation. If your ADC is 8-bit, I think you need 16-bit to get true
exponential filter. Your filter's step response shall look like this

|output
|
|1                 +++++++++++++++++++++++++
|            ++++++
|        ++++
|     +++
|   ++
|  +
| +
|+
+--------------------------------------------------- time
0

Sorry if I say trivial things :))

JS> Does anyone know of a software library (source code) that I could port to
JS> the PIC for real-time filtering?  I'm grabbing A/D data and want to do some
JS> basic artifact removal in software (real-time hopefully, before sending it
JS> to another processor) but I need a starting place of some working code.  Any
JS> language would be fine...

--
Best regards,
 Oleg                            mailto: remove_this_word.sergin@fcita.dn.ua