Simple Maths Going Wrong

[Darrel Taylor]

Here's one that works real well.
But it requires PBP 2.60 for the ATN function.

The measured wind direction should be in the variable DIR.
Then GOSUB Avg_Wind

It works by averaging the SIN and COS separately for each sample.
Then converts those averages back to an angle with ATN.
Angles range from 0-255, representing 0-359 degrees.

CLEAR

DIR   VAR BYTE   ; Current sample of wind direction (0-255)
S     VAR BYTE   ; averaged SIN
C     VAR BYTE   ; averaged COS
Wind  VAR BYTE   ; final averaged wind direction
Temp  VAR BYTE   ; temporary variable

AvgCount  CON 10 ; amount of averaging to apply

;---------------------------------------------------------------
Avg_Wind:    ; average in one DIR sample
  Temp = SIN DIR+127
  S=(S*(AvgCount-1)+Temp)/AvgCount
  Temp = COS DIR+127
  C=(C*(AvgCount-1)+Temp)/AvgCount
  Wind = (C-127) ATN (S-127)
RETURN

;---------------------------------------------------------------
Set_Wind:    ; Sets average wind direction without averaging
  S = SIN DIR + 127
  C = COS DIR + 127
GOTO Avg_Wind

If you don't have 2.60, the same thing can probably be done with scalerobotics cordic trig routines.

HTH,