Servo Values to Degrees... How?

[paulcd2000]

but how can you convert tilt servo values into degrees. sorry, i'm kinda tired, so i might be being dense

EDIT: Would this work?

				angle= (TILT_SERVO-STOP)*0.75757575;
				distance = HEIGHT_DIFF/atan(angle);

.757575... is the degrees per servo step

[Ianuser]

So, wait a minute. I wrote this:
unsigned float Find_Distance(void)
{
float radian;
float range;
radian = ((((angle I will measure in degrees that the tilt servo has to offer from down to up) / 256) * pi) / 180) * pwm07(which is my tilt_servo pwm);
range = (116 - (distance I have yet to measure between the floor and my camera because we haven't placed it yet)) / tan(radian);
}

I read on another thread that the angle has to be in radians for the Tan() function to take in. Also, I put this in Tracking.c. Does it matter where I place this function? SO, my real questions are, Does anything about what I wrote make sense? And how does this compare to the:
pan angle = ((current pan PWM) - (pan center PWM)) * degrees/pan PWM step that was stated earlier in this thread (other than I'm looking for tilt rather than pan) Do I have to subtract my pwm07 by 124 like you did in this one? Sorry if I'm being confusing, but I'm trying to understand all of this at once. I also have questions about why my camera doesn't work PERIOD. It's all hooked up but it seems to not be getting power. Anyway, one thing at a time. Please help me if you can! Thanks

[gnirts]

Originally Posted by paulcd2000

but how can you convert tilt servo values into degrees. sorry, i'm kinda tired, so i might be being dense

EDIT: Would this work?

                angle= (TILT_SERVO-STOP)*0.75757575;
                distance = HEIGHT_DIFF/atan(angle);

.757575... is the degrees per servo step

I am pretty sure you want tan() and not atan()

Good luck,
Robinson

[jdejoannis]

From "The C Library Reference Guide, 1997, Eric Huss" (available online):

2.7.2.9 tan
Declaration:

double tan(double x);

Returns the tangent of a radian angle x.

Range:

There is no range limit on the argument or return value.

In short - yes, the angle is in radians (and it should be a double).

[Ianuser]

This is what I have now, I have no idea if it is going to work. Please help if you can.
My tilt_servo is pwm07, my default MAX for tilt is 194, min is 94, center is 144, step is 50. QUESTION: if I change the step to 25, will it automatically make twice as many steps? will it cut the time in half? how is that programmed. ALSO, DOES THIS MAKE ANY SENSE????

const rom unsigned short targetRange[] =
{
    USHRT_MAX,  // zero index is undefined
5519,
2759,
1839,
1102,
918,
787,
688,
611,
549,
499,
457,
421,
390,
364,
340,
320,
302,
285,
270,
257,
234,
223,
214,
205,
197,
189,
182,
176,
169,
163,
158,
153,
148,
143,
139,
134,
130,
127,
123,
119,
116,
110,
107,
104,
101,
99,
96,
94,
91,
89,
87,
85,
82,
80,
78,
76,
75,
73,
71,
69,
68,
66,
64,
63,
61,
60,
58,
57,
55,
54,
53,
51,
50,
49,
48,
46,
45,
44,
43,
42,
40,
39,
38,
37,
36,
35,
34,
33,
32,
31,
30,
29,
28,
27,
26,
25,
24,
23,
22,
21,
20,
19,
18,
18,
17,
16,
15,
14,
13,
12,
11,
11,
10,
9,
8,
7,
6,
5,
5,
4,
3,
2,
1,
0
};

unsigned int Find_Distance(void)
{
	return(targetRange[pwm07-67]);
}

Those numbers in the array are the distance for each pwm index all the way up to 127 (90 degrees approximately). How does this relate to my 94 min, 194max for my tilt servo? Don't i have to change those to make this work? I'm a little confused. THanks!

[jdejoannis]

Thats an interesting idea. Essentially you prefer to tabulate rather than calculate the tangent. In principle, I have no objections. You can choose whatever step size and range you want for the tracking. Those won't affect the range calculation because they are merely properties of the search algorithm (see tracking.c). You will be taking the pwm value after the search is over and the camera is locked on. I am not sure why you are subtracting 67 from the pwm lookup. Shouldn't it be the tilt min 94?

Jason

[#root:]

Hey, I've been having a problem setting the correct degrees to a variable, even though it prints to the terminal correctly.

pan_angle = (((int)PAN_SERVO - 124) * 65)/124;
tilt_angle = (((int)TILT_SERVO - 144) * 25)/50;

I have tried making these variables ints, floats, and doubles (they are global static declared in user_routines.h, set in terminal.c, and used in user_routines_fast.c). Would it help if I cast pan_angle and tilt_angle as ints or changed 124 to 124.0? Maybe if I did

(int) pan_angle = (int) (((int)PAN_SERVO - 124) * 0.5242);

Any help would be appreciated. Thanks!

[#root:]

I would appreciate any help, especially if you had problems using the bells and whistles camera code versus the regular one.

Thanks

[jerry w]

Originally Posted by #root:

Hey, I've been having a problem setting the correct degrees to a variable, even though it prints to the terminal correctly.

pan_angle = (((int)PAN_SERVO - 124) * 65)/124;
tilt_angle = (((int)TILT_SERVO - 144) * 25)/50;

I have tried making these variables ints, floats, and doubles (they are global static declared in user_routines.h, set in terminal.c, and used in user_routines_fast.c). Would it help if I cast pan_angle and tilt_angle as ints or changed 124 to 124.0? Maybe if I did

(int) pan_angle = (int) (((int)PAN_SERVO - 124) * 0.5242);

Any help would be appreciated. Thanks!

Be careful when declaring variables. They should not be declared in the header file. The header is used in several places, which can cause copies of variables to occur.
In the user.c you should have;

int   pan_angle = 0 ;

In user.h you should have;

extern int   pan_angle ;

Then user_fast.c will see the external variable when the header is read.

Jerry w

[#root:]

I tried to declare it as an extern, but I was having trouble using and then accessing the variable in both terminal.c and user_routines_fast.c.

Well, hopefully I can figure it out by the time the competition starts!