Cordic trig assembly code for PIC18f

[Art]

Nice work, but I am also challenged with maths.
Will this allow me to do point rotation?

Say I have an origin x=0 & y=0, and another point x=4, y=4.
Can I find out the angle of the second coordinates where the first set is the origin,
and then rotate the second point say 180 degrees around the origin ?
Art.

[Art]

Uh-oh.. just including the line:
include "trig-pic16.inc"
causes this:

Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 213 : [235] Opcode Expected Instead of 'dt'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 216 : [235] Opcode Expected Instead of 'dt'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 219 : [235] Opcode Expected Instead of 'dt'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 222 : [235] Opcode Expected Instead of 'dt'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 237 : [226] Numeric Constant or Symbol Name Expected
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 239 : [226] Numeric Constant or Symbol Name Expected
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 269 : [235] Opcode Expected Instead of 'movfw'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 283 : [235] Opcode Expected Instead of 'movfw'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 301 : [235] Opcode Expected Instead of 'movfw'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 306 : [235] Opcode Expected Instead of 'movfw'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 316 : [235] Opcode Expected Instead of 'movfw'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 321 : [235] Opcode Expected Instead of 'movfw'
Error C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 349 : [235] Opcode Expected Instead of 'movfw'
Warn C:\PROGRA~1\MPLAB\PROJECT\SCROLL.ASM 934 : [102] Code Crosses Boundary @ 800h

I'm using a 16F877 too.

[Darrel Taylor]

Use MPASM for the assembler.
<br>

[Art]

Thanks Darrel,
I'm working on hardware now, but I'll try again as soon as possible.
Any idea on my first question?

[Art]

Use MPASM for the assembler.
<br>

It seems that this line becomes offensive:

'@ DEVICE LVP_OFF,BOD_OFF,HS_OSC				'

Which is how I set configuration.
Art.

[ScaleRobotics]

You need to use a different syntax for MPASM.

like this:

Example: To set the PIC for Internal Oscillator allowing use of the OSC pins as I/O...

@ __config _INTRC_OSC_NOCLKOUT

Only one config statement is allowed when using MPASM, so multiple definitions follow-on from each other each connected to it’s previous buddy with an &.

Example: Typical Settings for a 16F628…

@ __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON & _LVP_OFF & _CP_ALL & _DATA_CP_ON

More (much more) here: http://www.picbasic.co.uk/forum/showthread.php?t=543

[ScaleRobotics]

Nice work, but I am also challenged with maths.
Will this allow me to do point rotation?

Say I have an origin x=0 & y=0, and another point x=4, y=4.
Can I find out the angle of the second coordinates where the first set is the origin,
and then rotate the second point say 180 degrees around the origin ?
Art.

Hi Art,

You can definitely find the angle in the first part of your question. As far as rotation, I have to think a little more. Should be possible though.

Are you rotating one of your LED displays? If so, are we talking full rotation, or just 90, 180, 270 degrees?

[Art]

Ideally, to potentially be able to do full rotation of a pixel.
Yes, I have a matrix LED display in mind
I wouldn't care whether or not it is equally divided into 360 degrees.
I already have made routines that make it easy to draw to the screen.

I can do this in C on the Sony PSP like this

xx = 240;
yy = 30;
x = xx - 240;
y = yy - 136;

theta = rotation;
thetab = 360 - theta;
thetab = (3.141592 / 180) * theta;

xnew = cos(thetab)*x - sin(thetab)*y;
ynew = sin(thetab)*x + cos(thetab)*y;

xnew = xnew + 240;
ynew = ynew + 136;

Where x-240, y-136 are coordinates for the centre of the screen,
x-240,y-30 is the arbitrary point I want to rotate (the one given is a point directly above the centre of the screen),
rotation is the real angle 0-359 (0 can also be 360).
xnew and ynew are the new (rotated) coordinates.
I don't know if this works with microcontrollers even if you do use a C compiler.

[ScaleRobotics]

Ideally, to potentially be able to do full rotation of a pixel.
Yes, I have a matrix LED display in mind
I wouldn't care whether or not it is equally divided into 360 degrees.
I already have made routines that make it easy to draw to the screen.

I can do this in C on the Sony PSP like this

xx = 240;
yy = 30;
x = xx - 240;
y = yy - 136;

theta = rotation;
thetab = 360 - theta;
thetab = (3.141592 / 180) * theta;

xnew = cos(thetab)*x - sin(thetab)*y;
ynew = sin(thetab)*x + cos(thetab)*y;

xnew = xnew + 240;
ynew = ynew + 136;

Where x-240, y-136 are coordinates for the centre of the screen,
x-240,y-30 is the arbitrary point I want to rotate (the one given is a point directly above the centre of the screen),
rotation is the real angle 0-359 (0 can also be 360).
xnew and ynew are the new (rotated) coordinates.
I don't know if this works with microcontrollers even if you do use a C compiler.

Yes, it looks like you could use the same type of math. The cordic lets you compute sin and cos in a single operation. It is very quick with this type of thing, and can perform about 2000 of these per second.

So you would just have to solve:



as you have in your above equation. The PIC18 cordic is a little better, and I documented it more. But if you still want to do it with your PIC16, I am here to help.

Wikipedia talks a little bit about rotation here: http://en.wikipedia.org/wiki/Rotation_%28mathematics%29

[Art]

I'm not quite ready to do it yet, only because I'm in the middle of something else,
but regarding the LED displays, I've got a blitter routine handling sprites now.
It would be really nice to see if it could handle rotation of a sprite (pixel by pixel).

Thanks for your offer to help, I'll surely take you up on it very soon

[B-O Eliasson]

Hi !
I'm trying to write a program to calculate sunrise and sunset. The pic is 18F2550 and I'm using long variables and PBPL. I've tried to use the TRIG.INC but it seems that I cant use it in PBPL, Error: DIV32. Is there a way to rewrite the program so that it will work with PBPL?
I'm using Picbasic Pro 2.50 and MPASM 8.15.
Bernt-Ove

[B-O Eliasson]

The problem is solved. I found another version of trig.inc in post 13, and it works well for me. I have to put the word variables x,y into long variables before doing any calculations on them.

[readitaloud]

Hi,

I am using your TRIG.inc in a small program. The values appear correct from (ang) = 0 to 9000, 0 to 90.00 degrees. For values, 9000 < (ang) < 18000 ,the
values for x and y appear to switch. As an example with an (ang) value of 8900 or 89.00 degrees I receive a value back x = 29995 and y = 525. This seems correct.
For an (ang) value of 9100 or 91.00 degrees I receive back x = -523 and y = 29995. For 91.00 degrees I would expect x = 29995 and y = -523 ?

- Martin