Joystick Input Mapping

[ExarKun666]

This last competition for 2008, in my teleop code I had around 2000 lines of code just basically going like this:
if (p1_y == 0)
{
pwm13 = 0;
}
and ect... for all of them, what I was trying to accomplish was a slow steady raise in speed the more you push the controller forward, the method I used proved to be ineffective. I might also add when I was programming for this I was using the controllers that came in the kit of parts. Has anyone had any success doing what I tried to achieve? If so plz either tell me or instruct me in a different path, on how to accomplish this task.

[Branden Ghena]

Is there a reason why you couldn't put:

pwm13 = p1_y;

[JimWright949]

We do a few things, first we make everything into a signed char, and set the middle point of the joystick or PWM to 0, to get a range of -128 to 127, this makes things a bit easier to handle.

For our joystick input we put everything through a curve that we calc' in a speadsheet and then convert to a table like this:

#define curveXX curve18
char curve18[] =
{
0 , 0 , 0 , 1 , 1 , 1 , 2 , 2 , 3 , 3 , 4 , 4 , 5 , 5 , 6 , 6 ,
7 , 8 , 8 , 9 , 10 , 10 , 11 , 12 , 12 , 13 , 14 , 15 , 15 , 16 , 17 , 18 ,
18, 19 , 20 , 21 , 22 , 23 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ,
33 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 47 , 48 ,
49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 60 , 61 , 62 , 63 , 64 , 65 ,
66 , 68 , 69 , 70 , 71 , 72 , 74 , 75 , 76 , 77 , 78 , 80 , 81 , 82 , 83 , 85 ,
86 , 87 , 88 , 90 , 91 , 92 , 93 , 95 , 96 , 97 , 99 , 100, 101, 103, 104, 105,
107, 108, 109, 111, 112, 113, 115, 116, 117, 119, 120, 121, 123, 124, 126, 127
};

char GetCurve(char raw)
{
if (raw < 0)
return -curveXX[-raw];
else
return curveXX[raw];
}

This alows us to tweek the curve by hand if we need to.

-Jim

[dtengineering]

Is there a reason why you couldn't put:

pwm13 = p1_y;

I believe the goal here is exponential mapping... reducing sensitivity of the joystick near neutral values, while maintaing a full range of output values.

Some key terms to search CD for are:

joystick mapping exponential lookup

Using all of those or some combination thereof will provide lots of discussion on this topic.

Another good place to look is in the "white papers", where you will find resources far more extensive than in any one post. This one (http://www.chiefdelphi.com/media/papers/1639) might be helpful.

Jason

[Branden Ghena]

I believe the goal here is exponential mapping...


Ohhhh.....

Well in that case an array is probably a good idea.

[programMORT11]

Why not use a proportional increment like


static char flag;
if(joy_flag == 0) {
old_joy = p1_y;
flag =1;
}
else {
if(old_joy < p1_y && (p1_y != 127))
new_joy+=5;
else if (old_joy < p1_y && (p1_y != 127))
new_joy -= 5;
else
new_joy = 0;
flag = 0;

}
p1_y = old_joy + new_joy;

[ExarKun666]

Is there a reason why you couldn't put:

pwm13 = p1_y;

The reason was because I was trying to make it less sensitive then it was, it was really sensitive. (Basically it seemed to just go full blast just by slightly moving the joysticks forward and back.)

[yongkimleng]

I think the lookup table as JimWright949 suggested is the right way to go. You could put the values in an Excel sheet and tweak it until it gives you the graph you want, and then put it back into your code.

As a side note, this would go in before any PID, accel/decel, limiting code you may have.

[Mr. Lim]

The lookup tables suggested earlier are definitely the way to go.

If you're looking for a quick and dirty method to test things out, you can also try:


temp_p1_long = (signed long)p1_y - 127;
pwm01 = (unsigned char)(((temp_p1_long * temp_p1_long * temp_p1_long) >> 14) + 127);

temp_p2_long = (signed long)p2_y - 127;
pwm02 = (unsigned char)(((temp_p2_long * temp_p2_long * temp_p2_long) >> 14) + 127);


It's a cubic transfer function that we've used since 2004. If it works for you, you're eventually better off calculating the values from the function, and using a look-up table for competition. The long integer operations are a bit wasteful, but it's four quick lines of code for testing!

[ExarKun666]

if (p1_y == 0)
{
LEFT_MOTOR = 0;
}
if (p1_y == 1)
{
LEFT_MOTOR = 1;
}
if (p1_y == 2)
{
LEFT_MOTOR = 2;
}
if (p1_y == 3)
{
LEFT_MOTOR = 3;
}
if (p1_y == 4)
{
LEFT_MOTOR = 4;
}
if (p1_y == 5)
{
LEFT_MOTOR = 5;
}
if (p1_y == 6)
{
LEFT_MOTOR = 5;
}
if (p1_y == 7)
{
LEFT_MOTOR = 5;
}
if (p1_y == 8)
{
LEFT_MOTOR = 5;
}
if (p1_y == 9)
{
LEFT_MOTOR = 5;
}
if (p1_y == 10)
{
LEFT_MOTOR = 10;
}
if (p1_y == 11)
{
LEFT_MOTOR = 10;
}
if (p1_y == 12)
{
LEFT_MOTOR = 10;
}
if (p1_y == 13)
{
LEFT_MOTOR = 10;
}
if (p1_y == 14)
{
LEFT_MOTOR = 10;
}
if (p1_y == 15)
{
LEFT_MOTOR = 10;
}
if (p1_y == 16)
{
LEFT_MOTOR = 10;
}
if (p1_y == 17)
{
LEFT_MOTOR = 20;
}
if (p1_y == 18)
{
LEFT_MOTOR = 20;
}
if (p1_y == 19)
{
LEFT_MOTOR = 20;
}
if (p1_y == 20)
{
LEFT_MOTOR = 20;
}
if (p1_y == 21)
{
LEFT_MOTOR = 20;
}
if (p1_y == 22)
{
LEFT_MOTOR = 30;
}
if (p1_y == 23)
{
LEFT_MOTOR = 30;
}
if (p1_y == 25)
{
LEFT_MOTOR = 30;
}
if (p1_y == 26)
{
LEFT_MOTOR = 30;
}
if (p1_y == 27)
{
LEFT_MOTOR = 40;
}
if (p1_y == 28)
{
LEFT_MOTOR = 40;
}
if (p1_y == 29)
{
LEFT_MOTOR = 40;
}
if (p1_y == 30)
{
LEFT_MOTOR = 40;
}
if (p1_y == 31)
{
LEFT_MOTOR = 40;
}
if (p1_y == 32)
{
LEFT_MOTOR = 50;
}
if (p1_y == 33)
{
LEFT_MOTOR = 50;
}
if (p1_y == 34)
{
LEFT_MOTOR = 50;
}
if (p1_y == 35)
{
LEFT_MOTOR = 50;
}
if (p1_y == 36)
{
LEFT_MOTOR = 50;
}
if (p1_y == 37)
{
LEFT_MOTOR = 50;
}
if (p1_y == 38)
{
LEFT_MOTOR = 50;
}
if (p1_y == 39)
{
LEFT_MOTOR = 50;
}
if (p1_y == 40)
{
LEFT_MOTOR = 50;
}
if (p1_y == 41)
{
LEFT_MOTOR = 50;
}
if (p1_y == 42)
{
LEFT_MOTOR = 60;
}
if (p1_y == 43)
{
LEFT_MOTOR = 60;
}
if (p1_y == 44)
{
LEFT_MOTOR = 60;
}
if (p1_y == 45)
{
LEFT_MOTOR = 60;
}
if (p1_y == 46)
{
LEFT_MOTOR = 60;
}
if (p1_y == 47)
{
LEFT_MOTOR = 60;
}
if (p1_y == 48)
{
LEFT_MOTOR = 60;
}
if (p1_y == 49)
{
LEFT_MOTOR = 60;
}
if (p1_y == 50)
{
LEFT_MOTOR = 60;
}
if (p1_y == 51)
{
LEFT_MOTOR = 60;
}
if (p1_y == 52)
{
LEFT_MOTOR = 70;
}
if (p1_y == 53)
{
LEFT_MOTOR = 70;
}
if (p1_y == 54)
{
LEFT_MOTOR = 70;
}
if (p1_y == 55)
{
LEFT_MOTOR = 70;
}
if (p1_y == 56)
{
LEFT_MOTOR = 70;
}
if (p1_y == 57)
{
LEFT_MOTOR = 70;
}
if (p1_y == 58)
{
LEFT_MOTOR = 70;
}
if (p1_y == 59)
{
LEFT_MOTOR = 70;
}
if (p1_y == 60)
{
LEFT_MOTOR = 70;
}
if (p1_y == 61)
{
LEFT_MOTOR = 70;
}
if (p1_y == 62)
{
LEFT_MOTOR = 85;
}
if (p1_y == 63)
{
LEFT_MOTOR = 85;
}
if (p1_y == 64)
{
LEFT_MOTOR = 85;
}
if (p1_y == 65)
{
LEFT_MOTOR = 85;
}
if (p1_y == 66)
{
LEFT_MOTOR = 85;
}
if (p1_y == 67)
{
LEFT_MOTOR = 85;
}
if (p1_y == 68)
{
LEFT_MOTOR = 85;
}
if (p1_y == 69)
{
LEFT_MOTOR = 85;
}
if (p1_y == 70)
{
LEFT_MOTOR = 85;
}
if (p1_y == 71)
{
LEFT_MOTOR = 85;
}
if (p1_y == 72)
{
LEFT_MOTOR = 95;
}
if (p1_y == 73)
{
LEFT_MOTOR = 95;
}
if (p1_y == 74)
{
LEFT_MOTOR = 95;
}
if (p1_y == 75)
{
LEFT_MOTOR = 95;
}
if (p1_y == 76)
{
LEFT_MOTOR = 95;
}
if (p1_y == 77)
{
LEFT_MOTOR = 95;
}
if (p1_y == 78)
{
LEFT_MOTOR = 95;
}
if (p1_y == 79)
{
LEFT_MOTOR = 95;
}
if (p1_y == 80)
{
LEFT_MOTOR = 95;
}
if (p1_y == 81)
{
LEFT_MOTOR = 95;
}
if (p1_y == 82)
{
LEFT_MOTOR = 105;
}
if (p1_y == 83)
{
LEFT_MOTOR = 105;
}
if (p1_y == 84)
{
LEFT_MOTOR = 105;
}
if (p1_y == 85)
{
LEFT_MOTOR = 105;
}
if (p1_y == 86)
{
LEFT_MOTOR = 105;
}
if (p1_y == 87)
{
LEFT_MOTOR = 105;
}
if (p1_y == 88)
{
LEFT_MOTOR = 105;
}
if (p1_y == 89)
{
LEFT_MOTOR = 105;
}
if (p1_y == 90)
{
LEFT_MOTOR = 105;
}
if (p1_y == 91)
{
LEFT_MOTOR = 105;
}
if (p1_y == 92)
{
LEFT_MOTOR = 110;
}
if (p1_y == 93)
{
LEFT_MOTOR = 110;
}
if (p1_y == 94)
{
LEFT_MOTOR = 110;
}
if (p1_y == 95)
{
LEFT_MOTOR = 110;
}
if (p1_y == 96)
{
LEFT_MOTOR = 110;
}
if (p1_y == 97)
{
LEFT_MOTOR = 115;
}
if (p1_y == 98)
{
LEFT_MOTOR = 115;
}
if (p1_y == 99)
{
LEFT_MOTOR = 115;
}
if (p1_y == 100)
{
LEFT_MOTOR = 115;
}
if (p1_y == 101)
{
LEFT_MOTOR = 115;
}
if (p1_y == 102)
{
LEFT_MOTOR = 115;
}
if (p1_y == 103)
{
LEFT_MOTOR = 115;
}
if (p1_y == 104)
{
LEFT_MOTOR = 115;
}
if (p1_y == 105)
{
LEFT_MOTOR = 115;
}
if (p1_y == 106)
{
LEFT_MOTOR = 115;
}
if (p1_y == 107)
{
LEFT_MOTOR = 120;
}
if (p1_y == 108)
{
LEFT_MOTOR = 120;
}
if (p1_y == 109)
{
LEFT_MOTOR = 120;
}
if (p1_y == 110)
{
LEFT_MOTOR = 120;
}
if (p1_y == 111)
{
LEFT_MOTOR = 120;
}
if (p1_y == 112)
{
LEFT_MOTOR = 120;
}
if (p1_y == 113)
{
LEFT_MOTOR = 120;
}
if (p1_y == 114)
{
LEFT_MOTOR = 120;
}
if (p1_y == 115)
{
LEFT_MOTOR = 120;
}
if (p1_y == 116)
{
LEFT_MOTOR = 120;
}
if (p1_y == 117)
{
LEFT_MOTOR = 127;
}
if (p1_y == 118)
{
LEFT_MOTOR = 127;
}
if (p1_y == 119)
{
LEFT_MOTOR = 127;
}
if (p1_y == 120)
{
LEFT_MOTOR = 127;
}
if (p1_y == 121)
{
LEFT_MOTOR = 127;
}
if (p1_y == 122)
{
LEFT_MOTOR = 127;
}
if (p1_y == 123)
{
LEFT_MOTOR = 127;
}
if (p1_y == 124)
{
LEFT_MOTOR = 127;
}
if (p1_y == 125)
{
LEFT_MOTOR = 127;
}
if (p1_y == 126)
{
LEFT_MOTOR = 127;
}
if (p1_y == 127)
{
LEFT_MOTOR = 127;
}
if (p1_y == 128)
{
LEFT_MOTOR = 127;
}
if (p1_y == 129)
{
LEFT_MOTOR = 127;
}
if (p1_y == 130)
{
LEFT_MOTOR = 127;
}
if (p1_y == 131)
{
LEFT_MOTOR = 127;
}
if (p1_y == 132)
{
LEFT_MOTOR = 127;
}
if (p1_y == 133)
{
LEFT_MOTOR = 127;
}
if (p1_y == 134)
{
LEFT_MOTOR = 127;
}
if (p1_y == 135)
{
LEFT_MOTOR = 127;
}
if (p1_y == 136)
{
LEFT_MOTOR = 127;
}
if (p1_y == 137)
{
LEFT_MOTOR = 127;
}
if (p1_y == 138)
{
LEFT_MOTOR = 130;
}
if (p1_y == 139)
{
LEFT_MOTOR = 130;
}
if (p1_y == 140)
{
LEFT_MOTOR = 135;
}
if (p1_y == 141)
{
LEFT_MOTOR = 135;
}
if (p1_y == 142)
{
LEFT_MOTOR = 135;
}
if (p1_y == 143)
{
LEFT_MOTOR = 135;
}
if (p1_y == 144)
{
LEFT_MOTOR = 135;
}
if (p1_y == 145)
{
LEFT_MOTOR = 135;
}
if (p1_y == 146)
{
LEFT_MOTOR = 135;
}
if (p1_y == 147)
{
LEFT_MOTOR = 135;
}
if (p1_y == 148)
{
LEFT_MOTOR = 135;
}
if (p1_y == 149)
{
LEFT_MOTOR = 140;
}
if (p1_y == 150)
{
LEFT_MOTOR = 140;
}
if (p1_y == 151)
{
LEFT_MOTOR = 140;
}
if (p1_y == 152)
{
LEFT_MOTOR = 140;
}
if (p1_y == 153)
{
LEFT_MOTOR = 140;
}
if (p1_y == 154)
{
LEFT_MOTOR = 140;
}
if (p1_y == 155)
{
LEFT_MOTOR = 140;
}
if (p1_y == 156)
{
LEFT_MOTOR = 140;
}
if (p1_y == 157)
{
LEFT_MOTOR = 140;
}
if (p1_y == 158)
{
LEFT_MOTOR = 140;
}
if (p1_y == 159)
{
LEFT_MOTOR = 145;
}
if (p1_y == 160)
{
LEFT_MOTOR = 145;
}
if (p1_y == 161)
{
LEFT_MOTOR = 145;
}
if (p1_y == 162)
{
LEFT_MOTOR = 145;
}
if (p1_y == 163)
{
LEFT_MOTOR = 145;
}
if (p1_y == 164)
{
LEFT_MOTOR = 150;
}
if (p1_y == 165)
{
LEFT_MOTOR = 150;
}
if (p1_y == 166)
{
LEFT_MOTOR = 150;
}
if (p1_y == 167)
{
LEFT_MOTOR = 150;
}
if (p1_y == 168)
{
LEFT_MOTOR = 150;
}
if (p1_y == 169)
{
LEFT_MOTOR = 150;
}
if (p1_y == 170)
{
LEFT_MOTOR = 150;
}
if (p1_y == 171)
{
LEFT_MOTOR = 150;
}
if (p1_y == 172)
{
LEFT_MOTOR = 150;
}
if (p1_y == 173)
{
LEFT_MOTOR = 150;
}
if (p1_y == 174)
{
LEFT_MOTOR = 160;
}
if (p1_y == 175)
{
LEFT_MOTOR = 160;
}
if (p1_y == 176)
{
LEFT_MOTOR = 160;
}
if (p1_y == 177)
{
LEFT_MOTOR = 160;
}
if (p1_y == 178)
{
LEFT_MOTOR = 160;
}
if (p1_y == 179)
{
LEFT_MOTOR = 160;
}
if (p1_y == 180)
{
LEFT_MOTOR = 160;
}
if (p1_y == 181)
{
LEFT_MOTOR = 160;
}
if (p1_y == 182)
{
LEFT_MOTOR = 160;
}
if (p1_y == 183)
{
LEFT_MOTOR = 160;
}
if (p1_y == 184)
{
LEFT_MOTOR = 170;
}
if (p1_y == 185)
{
LEFT_MOTOR = 170;
}
if (p1_y == 186)
{
LEFT_MOTOR = 170;
}
if (p1_y == 187)
{
LEFT_MOTOR = 170;
}
if (p1_y == 188)
{
LEFT_MOTOR = 170;
}
if (p1_y == 189)
{
LEFT_MOTOR = 170;
}
if (p1_y == 190)
{
LEFT_MOTOR = 170;
}
if (p1_y == 191)
{
LEFT_MOTOR = 170;
}
if (p1_y == 192)
{
LEFT_MOTOR = 170;
}
if (p1_y == 193)
{
LEFT_MOTOR = 170;
}
if (p1_y == 194)
{
LEFT_MOTOR = 185;
}
if (p1_y == 195)
{
LEFT_MOTOR = 185;
}
if (p1_y == 196)
{
LEFT_MOTOR = 185;
}
if (p1_y == 197)
{
LEFT_MOTOR = 185;
}
if (p1_y == 198)
{
LEFT_MOTOR = 185;
}
if (p1_y == 199)
{
LEFT_MOTOR = 185;
}
if (p1_y == 200)
{
LEFT_MOTOR = 185;
}
if (p1_y == 201)
{
LEFT_MOTOR = 185;
}
if (p1_y == 202)
{
LEFT_MOTOR = 185;
}
if (p1_y == 203)
{
LEFT_MOTOR = 185;
}
if (p1_y == 204)
{
LEFT_MOTOR = 195;
}
if (p1_y == 205)
{
LEFT_MOTOR = 195;
}
if (p1_y == 206)
{
LEFT_MOTOR = 195;
}
if (p1_y == 207)
{
LEFT_MOTOR = 195;
}
if (p1_y == 208)
{
LEFT_MOTOR = 195;
}
if (p1_y == 209)
{
LEFT_MOTOR = 195;
}
if (p1_y == 210)
{
LEFT_MOTOR = 195;
}
if (p1_y == 211)
{
LEFT_MOTOR = 195;
}
if (p1_y == 212)
{
LEFT_MOTOR = 195;
}
if (p1_y == 212)
{
LEFT_MOTOR = 195;
}
if (p1_y == 213)
{
LEFT_MOTOR = 195;
}
if (p1_y == 214)
{
LEFT_MOTOR = 205;
}
if (p1_y == 215)
{
LEFT_MOTOR = 205;
}
if (p1_y == 216)
{
LEFT_MOTOR = 205;
}
if (p1_y == 217)
{
LEFT_MOTOR = 205;
}
if (p1_y == 218)
{
LEFT_MOTOR = 205;
}
if (p1_y == 219)
{
LEFT_MOTOR = 205;
}
if (p1_y == 220)
{
LEFT_MOTOR = 205;
}
if (p1_y == 221)
{
LEFT_MOTOR = 205;
}
if (p1_y == 222)
{
LEFT_MOTOR = 205;
}
if (p1_y == 223)
{
LEFT_MOTOR = 205;
}
if (p1_y == 224)
{
LEFT_MOTOR = 215;
}
if (p1_y == 225)
{
LEFT_MOTOR = 215;
}
if (p1_y == 226)
{
LEFT_MOTOR = 215;
}
if (p1_y == 227)
{
LEFT_MOTOR = 215;
}
if (p1_y == 228)
{
LEFT_MOTOR = 215;
}
if (p1_y == 229)
{
LEFT_MOTOR = 225;
}
if (p1_y == 230)
{
LEFT_MOTOR = 225;
}
if (p1_y == 231)
{
LEFT_MOTOR = 225;
}
if (p1_y == 232)
{
LEFT_MOTOR = 225;
}
if (p1_y == 233)
{
LEFT_MOTOR = 225;
}
if (p1_y == 234)
{
LEFT_MOTOR = 235;
}
if (p1_y == 235)
{
LEFT_MOTOR = 235;
}
if (p1_y == 236)
{
LEFT_MOTOR = 235;
}
if (p1_y == 237)
{
LEFT_MOTOR = 235;
}
if (p1_y == 238)
{
LEFT_MOTOR = 235;
}
if (p1_y == 239)
{
LEFT_MOTOR = 245;
}
if (p1_y == 240)
{
LEFT_MOTOR = 245;
}
if (p1_y == 241)
{
LEFT_MOTOR = 245;
}
if (p1_y == 242)
{
LEFT_MOTOR = 245;
}
if (p1_y == 243)
{
LEFT_MOTOR = 245;
}
if (p1_y == 244)
{
LEFT_MOTOR = 245;
}
if (p1_y == 245)
{
LEFT_MOTOR = 245;
}
if (p1_y == 246)
{
LEFT_MOTOR = 250;
}
if (p1_y == 247)
{
LEFT_MOTOR = 250;
}
if (p1_y == 248)
{
LEFT_MOTOR = 250;
}
if (p1_y == 249)
{
LEFT_MOTOR = 250;
}
if (p1_y == 250)
{
LEFT_MOTOR = 250;
}
if (p1_y == 251)
{
LEFT_MOTOR = 251;
}
if (p1_y == 252)
{
LEFT_MOTOR = 252;
}
if (p1_y == 253)
{
LEFT_MOTOR = 253;
}
if (p1_y == 254)
{
LEFT_MOTOR = 254;
}
if (p1_y == 255)
{
LEFT_MOTOR = 255;
}
So this is what I have as the code, and I also put it for the right motor as well, it sounds to me like putting it on a sheet of paper or on excel, and assigning values will give you the result above in my code. I am not sure, but that's what I am understanding

[JimWright949]

Um, hmm, well your getting kinda the idea, but we can replace the ifs with something smaller. Here is the code:

Put this code outside of a function (it's a long story why it needs to be outside of a function):

char curve[] = {
0, 1, 2, 4, 5, 5, 5, 5, 5, 10, 10, 10, 10, 10, 10, 10,
20, 20, 20, 20, 20, 30, 30, 30, 30, 40, 40, 40, 40, 40, 50, 50,
50, 50, 50, 50, 50, 50, 50, 50, 60, 60, 60, 60, 60, 60, 60, 60,
60, 60, 70, 70, 70, 70, 70, 70, 70, 70, 70, 70, 85, 85, 85, 85,
85, 85, 85, 85, 85, 85, 95, 95, 95, 95, 95, 95, 95, 95, 95, 95,
105, 105, 105, 105, 105, 105, 105, 105, 105, 105, 110, 110, 110, 110, 110, 115,
115, 115, 115, 115, 115, 115, 115, 115, 115, 120, 120, 120, 120, 120, 120, 120,
120, 120, 120, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
127, 127, 127, 127, 127, 127, 127, 130, 130, 135, 135, 135, 135, 135, 135, 135,
135, 135, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 145, 145, 145, 145,
145, 150, 150, 150, 150, 150, 150, 150, 150, 150, 150, 160, 160, 160, 160, 160,
160, 160, 160, 160, 160, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 185,
185, 185, 185, 185, 185, 185, 185, 185, 185, 195, 195, 195, 195, 195, 195, 195,
195, 195, 195, 195, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 215, 215,
215, 215, 215, 225, 225, 225, 225, 225, 235, 235, 235, 235, 235, 245, 245, 245,
245, 245, 245, 245, 250, 250, 250, 250, 250, 251, 252, 253, 254, 255, 255, 255 };

Now in your function, replace all the if statements with:

LEFT_MOTOR = curve[p1_y];

The right motor will look like this:

RIGHT_MOTOR = curve[p2_y];

This make the p1_y into the index of the table that is in ram. The value of the table at the index p1_y will be put into LEFT_MOTOR.

You may get a linker error about being out of space if you are using MC18. If you do, find your .lkr file and open it up in MPLAB.

Find the section that looks like this:
DATABANK NAME=gpr0 START=0x60 END=0xFF PROTECTED
DATABANK NAME=gpr1 START=0x100 END=0x1FF
DATABANK NAME=gpr2 START=0x200 END=0x2FF
DATABANK NAME=gpr3 START=0x300 END=0x3FF
DATABANK NAME=gpr4 START=0x400 END=0x4FF
DATABANK NAME=gpr5 START=0x500 END=0x5FF
DATABANK NAME=gpr6 START=0x600 END=0x6FF
DATABANK NAME=gpr7 START=0x700 END=0x7FF
DATABANK NAME=gpr8 START=0x800 END=0x8FF
DATABANK NAME=gpr9 START=0x900 END=0x9FF
DATABANK NAME=gpr10 START=0xA00 END=0xAFF
DATABANK NAME=gpr11 START=0xB00 END=0xBFF
DATABANK NAME=gpr12 START=0xC00 END=0xCFF

Delete one of the lines and add 100 to the end of the line above it. Here is mine where I delete grp2 and add 100 to grp1's end tag:
DATABANK NAME=gpr0 START=0x60 END=0xFF PROTECTED
DATABANK NAME=gpr1 START=0x100 END=0x2FF
DATABANK NAME=gpr3 START=0x300 END=0x3FF
DATABANK NAME=gpr4 START=0x400 END=0x4FF
DATABANK NAME=gpr5 START=0x500 END=0x5FF
DATABANK NAME=gpr6 START=0x600 END=0x6FF
DATABANK NAME=gpr7 START=0x700 END=0x7FF
DATABANK NAME=gpr8 START=0x800 END=0x8FF
DATABANK NAME=gpr9 START=0x900 END=0x9FF
DATABANK NAME=gpr10 START=0xA00 END=0xAFF
DATABANK NAME=gpr11 START=0xB00 END=0xBFF
DATABANK NAME=gpr12 START=0xC00 END=0xCFF

Then it should link.

-Jim

[ExarKun666]

Curious, I was never successful in putting this kind of mapping on one controller, and we had an issue where one of the people, our next best driver, had to fill in at nationals, but he was really good wit one control joystick, so how would you map the curve for one joystick, for both motors, is it the same and you just say:
RIGHT_MOTOR = p1_y;
LEFT_MOTOR = p1_y;
then use the curve above? or do you do something different??

[JimWright949]

Hmm, at this point what I would have you do, is put the robot up on blocks and download the code to it to see what happens. However since I'm not near you, I can't have you do that.

What your code will do is just move the robot forward or backward, there will not be any turning. To turn you can copy some code.

If you are using the FrcCode_2007_8722 code base from the ifi site, find the user_routines.c file, and on line 238 you will find this code:

/*---------- 1 Joystick Drive ----------------------------------------------
*--------------------------------------------------------------------------
* This code mixes the Y and X axis on Port 1 to allow one joystick drive.
* Joystick forward = Robot forward
* Joystick backward = Robot backward
* Joystick right = Robot rotates right
* Joystick left = Robot rotates left
* Connect the right drive motors to PWM13 and/or PWM14 on the RC.
* Connect the left drive motors to PWM15 and/or PWM16 on the RC.
*/
p1_x = 255 - p1_y;
p1_y = 255 - pwm05;

pwm13 = pwm14 = Limit_Mix(2000 + p1_y + p1_x - 127);
pwm15 = pwm16 = Limit_Mix(2000 + p1_y - p1_x + 127);

This maps one joystick to two motors (really four but two are the same). After these lines add:

pwm13 = curve[pwm13];
pwm14 = curve[pwm14];
pwm15 = curve[pwm15];
pwm16 = curve[pwm16];

That will give you the one joystick drive and the curve that you want.

You will have to add the curve array from my post above to the code, put it somewhere like line 31 which is outside of functions.

-Jim

[ExarKun666]

Okay, well as soon as our robot gets back from Atlanta, and I am aloud to go program on it, I will post up on this thread what happened using the curve way you described to me earlier, ty for all the advice, I have been having real problems with this lately.

[Racer26]

1075 has always done the floating point operations on the fly in our controller, but our CPU isnt doing much (any, really) difficult math so its no big deal... Though this year we discovered that we had been using the wrong equation for the curve for like 3 years... oops.