Posted by Jerry Eckert.
Engineer from Looking for a team in Raleigh, NC sponsored by .
Posted on 3/15/2000 9:43 PM MST
In Reply to: Re: please explain more... posted by Jerry Eckert on 3/15/2000 8:48 PM MST:
:
: : As for losing part of our range, when I attempted to scale down the drive train output to 50% of the joystick value in order to create our 'turbo boost' function, using the code shown below:
: : (for forward)
: : p1_yfilt = (p1_yfilt)/2 min 128 max 254
: : (for reverse)
: : p1_yfilt = (p1_yfilt*3)/2 min 0 max 126
: : in one direction, i would lose all output unless the 'turbo' function was on, and in the other, it would always act as if the turbo was turned on.
: I don't have the PBASIC manual handy, but it looks like the problem might be that the precedence of min/max is higher than division. In other words, I suspect PBASIC evaluated your statements as:
: p1_yfilt = (p1_yfilt)/(2 min 128 max 254), and
: p1_yfilt = (p1_yfilt*3)/(2 min 0 max 126)
: Try rewriting them as follows:
: p1_yfilt = (p1_yfilt/2) min 128 max 254, and
: p1_yfilt = ((p1_yfilt*3)/2) min 0 max 126
Let me try this again... (I should know better than to try to do this stuff when I've been sitting in front of a computer for 48+ hours.
)
The min/max precedence MAY be the problem; if it isn't, the scaling formulas are also wrong.
In forward: (.le. = less than/equal; .ge. = greater than/equal)
Before scaling, 128 .ge. p1_yfilt .le. 254
64 .ge. p1_yfilt/2 .le. 127
Therefore, regardless of the input value, the scaled p1_yfilt will be forced to 128 (no output) by the MIN.
Reverse:
Before scaling: 0 .ge. p1_yfilt .le 126
0 .ge. p1_yfilt*3/2 .le. 189
For reverse you should get some output, but the stick range is going to be heavily biased towards neutral output after the MIN/MAX are applied.
I'd do something like this (please excuse any syntax errors - it's been a year since I've programmed PBASIC):
LOOKDOWN p1_yfilt, (lt)[127,128,255],index ('(lt)' is less than sign)
BRANCH index,[rev,neutral,fwd]
REV:
p1_yfilt = (126-((126-p1_yfilt)/2)) min 0 max 126
goto common
NEUTRAL:
p1_yfilt = 127
goto common
FWD:
p1_yfilt = (128+((p1_yfilt-128)/2)) min 128 max 254
COMMON:
If the LOOKUP function will accept formulas in the value list, all of the above starting at the BRANCH can be replaced by:
LOOKUP index,[((126-((126-p1_yfilt)/2)) min 0 max 126), 127, ((128+((p1_yfilt-128)/2)) min 128 max 254)]
If you want a dead zone around the neutral joystick position, replace the LOOKDOWN with:
LOOKDOWN p1_yfilt,(lt)[127-dead_size, 128+dead_size, 255]
: Jerry