From Tony Nixon [sales at picnpoke.com] and Scott Dattalo
Heres a simple setup using the FSR. Averages for 8 readings though.CBLOCK Average: 8h tempH tempL ENDC movlw Average ; initialise FSR movwf FSR ... ; ; PLACE A2D RESULTS INTO A ROTATING BUFFER ; movf ADRES,W movwf INDF incf FSR movlw Average + 8h xorwf FSR,W btfss STATUS,Z goto NFSR movlw Average movwf FSR NFSR ... ;Scott Dattalo interjects: ;If you have only 8 samples, and you were willing to align the array on a mod 8 ;boundary, then advancing the pointer could be done easily: incf fsr,w andlw 7 addlw Average movwf fsr ;if you don't wish to align the array, then try this instead: incf fsr,w addlw -Average andlw 7 addlw Average movwf fsr ; ; AVERAGE OUT THE 8 STORED VALUES WHEN A RESULT IS NEEDED ; movlw Average movwf FSR clrf tempH clrf tempL avLoop movf INDF,W ; add up 8 word values addwf tempL btfsc STATUS,C incf tempH incf FSR movlw Average +8h xorwf FSR,W btfss STATUS,Z goto avLoop movlw Average movwf FSR bcf STATUS,C ; div result by 8 rrf tempH rrf tempL bcf STATUS,C rrf tempH rrf tempL bcf STATUS,C rrf tempH rrf tempL ....
And Scott also says:
Again, I think the best way to maintain a running average is by subtracting the oldest value and adding in the newest. Here's something I'll whip out as fast as I can type it - which means there's a good chance for a thinko.; avg_lo:avg_hi - 16bit cumulative sum of last 8 samples ; samples - a circular array that holds the last 8 samples ; assume that samples and avg_lo:avg_hi are initialized to zero ; ; FSR is initialized to the start of samples ; ; W = newest sample AVERAGE: addwf avg_lo,f ;add newest sample to the average skpnc incf avg_hi,f xorwf indf,f ; swap oldest and newest samples xorwf indf,w xorwf indf,f subwf avg_lo,f ;remove the oldest sample from the average skpc decf avg_hi,f incf fsr,w ;advance the sample pointer addlw -sample andlw 7 addlw sample movwf fsr return There - no more looping through all of the data after every sample is acquired. Now, I'm assuming that the division is not needed at every iteration. I tend to put off the difficult stuff as long as possible - often times, the intermediate calculations are more than sufficient. But, if you want, then this is how I'd do it: rrf avg_hi,w movwf temp_hi rrf avg_lo,w movwf temp_lo rrf temp_hi,f rrf temp_lo,f rrf temp_hi,f rrf temp_lo,w and if you wanted rounding: skpnc addlw 1 (You don't need to worry about clearing the carry because the average is guranteed to be less than or equal to 255.)
|file: /Techref/microchip/avga2d.htm, 8KB, , updated: 2006/1/24 13:17, local time: 2018/8/19 03:01,
|©2018 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?|
<A HREF="http://techref.massmind.org/techref/microchip/avga2d.htm"> PIC Microcontoller Input / Ouput Method Averaging A2D results</A>
|Did you find what you needed?|
Welcome to massmind.org!
Welcome to techref.massmind.org!