; Written by Andrew Warren [fastfwd at ix.netcom.com]. A couple days ago, I wrote that an averaging filter of the form: (WIDTH-1)*AVE + NEW AVE = ------------------- WIDTH was "absurdly simple" if WIDTH = 256. A couple of people have asked in private email for the code; here it is: AVEHI EQU [ANY FILE REGISTER] ;Holds the average [0-255]. AVELO EQU [ANY FILE REGISTER] ;Holds the fractional part ;of the average. NEW EQU [ANY FILE REGISTER] ;Holds the new sample. FILTER256: MOVF AVEHI,W SUBWF NEW,W SKPC DECF AVEHI ADDWF AVELO SKPNC INCF AVEHI 7 words, 7 instruction cycles, "NEW" is unchanged.
http://www.htsoft.com/cgi-bin/agnes?PicforumAgnes+PicforumAgnesHTMLArticle+2775.2 Frank Everest mentions very similar idea:+temp = (average - new) >> time_value average = average - tis a quick implementation of
average = ( (2^time_value - 1)*average + (1)*new ) / 2^time_value.
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<A HREF="http://techref.massmind.org/Techref/microchip/dsp/av-256w-aw.htm"> PIC Microcontoller DSP Math Method 8bit 16 step Averageing filter</A>
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