Adjusting Sensitivity/Scale of Controls

[Mr. Lim]

Originally Posted by ConKbot of Doom

Ive been looking at this problem, but rather than a software solution, I would be interested in a hardware solution. Ive been looking at using a potentiometer as a solution.

I would set up a resistor divider to get .5vcc from the OI and send that to pin 1 on the pot, the signal from the joystick would go to pin 3 and pin 2 would go to the input on the OI. That way the driver could adjust the scale quickly, from no scaling to locked at 127

I know the rules prohibit messing around inside joystick, but allow a custom control box, so I would think that a box in the middle would be in a bit of a grey area. Can anyone lend any clarification to this? I just think that why should we devote processor cycles to something that can be done in hardware so simply. Plus I'm more comfortable with electronics than coding, so I'm sure that plays a role in it too.

Tristan Lall did this to our robot last year using software. We use the older black Flightsticks which have a wheel on them. In fact, the default code still shows variables like "p1_wheel" from these old joysticks =).

The wheel worked as a speed limiter which would scale the total range of the joystick down. Our reason for this was to demo the robot to children, and allow them to drive without fear of breaking things.

I believe this code is UNTESTED, so programmer beware. However the concept alone should prove useful:

temp_scale_long = (unsigned long) (p1_wheel * 3) >> 2 + 64; //So what if it's stepwise? (Just say no to floats.)
  temp_tankx_long = (signed long)p1_x - 128;
  temp_tankx_char = (unsigned char)(((temp_tankx_long * temp_tankx_long * temp_tankx_long * temp_scale_long)  >> 22) + 128);
  temp_tanky_long = (signed long)p1_y - 128;
  temp_tanky_char = (unsigned char)(((temp_tanky_long * temp_tanky_long * temp_tanky_long * temp_scale_long)  >> 22) + 128);
  pwm01 = pwm03 = pwm05 = Limit_Mix(2000 + temp_tanky_char + temp_tankx_char - 127);
  pwm02= pwm04 = pwm06 = Limit_Mix(2000 + temp_tanky_char - temp_tankx_char + 127);

FYI, we did this in ADDITION to our cubic transfer function, and here Tristan (who once was a driver for Team188) has modified our tank drive code for his preferred one-stick drive.

Hope this helps!

-SlimBoJones...