Neutral for joysticks isn't 127

The neutral position for our joysticks is not 127, and this is making us mess up a bit. For the left side, neutral is 165, and for the right, neutral is 193. What could be causing this, and how do we make it go back to the original 127 position?

I’m assuming since you’re including numbers, the problem is the PWMs are neutral (solid yellow) when the values the RC outputs are 165 and 193, respectively - I’m assuming the problem isn’t in the calibration of wheel of the joystick.

Sometimes the victors get a little-bit screwey and don’t recognize the signal coming out of the RC correctly. There is a method to calibrate the actual victors. In page two of the IFI Victor 884 Users Manual, it has the instructions on what to do to calibrate the victor. After pressing a few things, you essentially move your joystick to full forward, full back, and the neutral position. The victor then detects what the signal coming out of the RC is at these positions and adjusts itself appropriately. Before you do this, though, I recommend you use the calibration wheel on the joystick to make sure when you move the joystick into neutral, the RC sees 127 as coming in.

If the neutral position is not 127 you can trim them by adjusting the wheel next to each axis on the joystick. Turn the wheel until both give you the 127 value you are looking for. Then find some heavy duty tape and hold them down so they won’t move again :wink:

Note: Not the thumb wheel which you can optionally use as an input. The adjustment wheels.

a small not, this year’s joysticks do not have thumb wheels. instead, they have the hat switches on top, which are mapped to the pX_wheel axis.

if you havnt edited the printf function in your code you can use that to esaly see what values your joysticks are. just move the trim wheel till it reads 127 ish. the output screen for printf function is the window that pops up after loading a program

we do have the printf function showing us a number of things through hyperterminal, and thats where we got the readings of 165 and 193 from.

adjust your trim tabs on the joysticks - the little black thumbnobs on the white base of the unit.

i have found that this years joysticks really don’t have that wonderful of a center position. we are using sticks from previous years… other than the trim tabs being off you may need to do some scaling. what we do is this

#define left_MAX 254
#defing left_MIN 16

pwm01 = ((pwm01 - left_MIN) * 256) / (left_MAX-left_MIN);

this is the basic way we do it. i don’t have the code with me but i know we break up the equation so we don’t lose as much in the dividing so that the dividing is easier on the proc.

197 is not a sloppy center position problem - thats halfway to full power :ahh:

and your code still wont help them if they dont adjust the trim tabs :^)

what you might wana try is to write a dead zone into code…
if(p1_x > 115 && p1_x <135) {p1_x = 127;}
just a thought.

Yeah, sounds like its a calibration problem, not a programming fix - can you clarify what you mean by “neutral”? If those numbers are what your RC is outputting to make the victors solid yellow (neutral), then it definately sounds like your victors are just out of whack and need to be recalibrated.

Use the dashboard app from IFI. The OI still spits to dashboard even if you don’t have the RC on. Make sure the jumper is on OI

Calibrate the Victors using the Victor 884 calibration procedure. Basically you hold down the calibration button on the victor with an allen wrench or other small tool while you move the joystick from center to full forward to full backward and back to center. The Victor’s LED should flash green once this procedure is complete.

I cannot discourage you enough not to mess with the calibration of the Victors.

Use the factory cals. The other way lies madness!

I am serious. Rescale your joysticks in code if you have to but I think you will be very very sorry if you start messing with the cals on the Victors.

There are lots of good reasons not to recal the Victor, but one of the best is that if you ever blow a Victor and replace it you will have to recal, and probably right before the championship round, if Murphy’s Law holds.

The non-centering joystick is easy to solve in software, stay away from the Cal button on your Victors…

Joe J.

I think the problem that they have though is that the ‘center’ is sooo far off that they are losing some resolution. If the center was at 135 instead of 127; it’s not that big a deal. But, when they are talking 190 something being a neutral then the joystick becomes very sensitive; even with scaling.

What specific things have been observed with the recal of Victors that is negative?


It’s not entirely a question of is it a bad thing to recalibrate the victor. You could actually lose power (voltage range) by calibrating them at an incorrect value. Recalibrating the victor is fixing the problem on the output, when the input is actually the culprit. Why not fix the input? The real problem.

Calibration of the speed controllers was only important on the early days of FIRST, particularly with the Tekens. Now with programmable control systems you can easilly correct the problem at the source: the trim of the joystick.