Thread: Scaling Values in the Control Program
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Unread 23-06-2002, 22:23
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#0047 (ChiefDelphi)
  
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Re: Here's a theory....
Posted by Jerry Eckert.

Engineer from Looking for a team in Raleigh, NC sponsored by .

Posted on 3/16/2000 8:26 AM MST


In Reply to: Here's a theory.... posted by Mike Gray on 3/16/2000 7:27 AM MST:




: For reverse: Assume that the filtered joystick value ranges from 127 to 255. You multiply by 3 and divide by 2, then clamp at 126, so the member never moves...UNTIL the joystick exceeds 170 counts. Since p1_yfilt is a single byte, it rolls over beyond 255 counts and its value then becomes 0. Full speed, turbo, wrong direction.

: Floating point math: 171*3/2=256.5

: Integer math: 171*3/2=0

Computations are performed using a 16-bit scratchpad and truncated, if necessary, when the final result is stored. In the example above, evaluation of the expression yields a result of 256. The MAX function then clamps the value at 126 before it is stored in the 8-bit destination.



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