2x16 LCD Graphics :)

[Art]

Thanks Guys,
I am having some trouble with diagonal lines and circles.
When you use a real gfx display with PBP, is it usually the display that
handles the lines and circles, or is it done in PBP?

I'm finding the algorithms are usually in C, and all seem to want to look
for values below zero (signed integer variables), where one of these
variables would wrap back to 0xFF if you decremented from zero using PBP

For the only diagonal lines in the video, I was able to do a trick and
check a value is above #128, pretending that value is zero.
This is so far only working if the destination point of the line has higher
x and y coordinates than the start point..
(ie. I can draw a line at any angle from x-0,y-0, to anywhere).

Here is the difference in the code.

x0 = 3 : y0 = 3
x1 = 21 : y1 = 11
gosub drawline

drawline:
	stepx = 0
	stepy = 0
	frac = 0
	'a line is x0,y0 to x1,y1.
	dy = y1 - y0
	dx = x1 - x0

	IF dy > 128 THEN
	dy = dy - 1
	stepy = stepy - 1
	ELSE
	stepy = 1
	ENDIF

	IF dx > 128 THEN
	dx = dx - 1
	stepx = stepx - 1
	ELSE
	stepx = 1
	ENDIF

	dy = dy << 1
	dx = dx << 1

    'draw pixel
	px = x0 : py = y0
	gosub setpixel
    
	IF (dx > dy || dx > 128) THEN

    frac = dy - (dx >> 1)
    WHILE x0 != x1
    IF (frac < 128) THEN
	y0 = y0 + stepy
 	frac = frac - dx
	ENDIF
    x0 = x0 + stepx
    frac = frac + dy
    'draw pixel
  	px = x0 : py = y0
	gosub setpixel
    WEND

	ELSE

    frac = dx - (dy >> 1)
    WHILE y0 != y1
    IF (frac < 128) THEN 
	x0 = x0 + stepx
	frac = frac - dy
	ENDIF
    y0 = y0 + stepy
    frac = frac + dx
    'draw pixel
	px = x0 : py = y0
	gosub setpixel
    WEND

	ENDIF

return

... and the original C

static void drawLine(int x0, int y0, int x1, int y1, int color, Color* destination, int width)
{
	int dy = y1 - y0;
	int dx = x1 - x0;
	int stepx, stepy;
	
	if (dy < 0) { dy = -dy;  stepy = -width; } else { stepy = width; }
	if (dx < 0) { dx = -dx;  stepx = -1; } else { stepx = 1; }
	dy <<= 1;
	dx <<= 1;
	
	y0 *= width;
	y1 *= width;
	destination[x0+y0] = color;
	if (dx > dy) {
		int fraction = dy - (dx >> 1);
		while (x0 != x1) {
			if (fraction >= 0) {
				y0 += stepy;
				fraction -= dx;
			}
			x0 += stepx;
			fraction += dy;
			destination[x0+y0] = color;
		}
	} else {
		int fraction = dx - (dy >> 1);
		while (y0 != y1) {
			if (fraction >= 0) {
				x0 += stepx;
				fraction -= dy;
			}
			y0 += stepy;
			fraction += dx;
			destination[x0+y0] = color;
		}
	}
}

I wonder what of the C compilers that are for 16F pics.
Maybe they don't do signed integers either?
If I could compile the original C source in a pic C compiler,
and then disassemble it, I could have the result in RISC asm.

[Jerson]

I am having some trouble with diagonal lines and circles.
When you use a real gfx display with PBP, is it usually the display that
handles the lines and circles, or is it done in PBP?

In a real graphic LCD, it is the user who draws the lines / circles using Bresenhams algorithm or a variant. PBP, C or ASM is just a matter of choice.

I am curious to know why you want to use a character lcd this way other than for the thrill of doing it. You only get 8 programmable characters which is about a 4th of the 16x2 display. Your demos too show repeated patterns. It is much more challenging and fun to get a graphic lcd come upto video speed (20fps and more).

[Art]

It is for the thrill.. and I figure the work is not wasted, because these LCDs do still get use.
I already did an LED matrix display with games, scroller etc., and I don't think it is getting any faster.
Also, I have not written for pics in some time, and needed something to get going.
There is room to duplicate the graphics screen, but for a practical application,
I figure the rest of the screen would have some text on it.

I have solved the line drawing, but if you have a way to draw circles in PBP it
would be appreciated At the moment my circles are perfect squares of the
correct radius, but I'm keeping that for squares since it beats defining all the corner coordinates

I would not buy a gfx LCD if I couldn't do the graphics, so it's a good way to come up with
the routines now. I would still like to do my own hardware/software mapping GPS one day.

I do plan to give it away when it's finished and cleaned up.


ps to mods, it would be great if you could delete every video posted here
(can seem to delete/edit my posts)
I've done the C-64/Amiga style Megademo

[Demon]

Videos removed.

Robert

[Art]

Thanks Robert, I combined everything into one retro demo:



I robbed the circle drawing from a GLCD code sample here, and added a bit more.
There are 10 sections to the demo, but they only last a few seconds each.
The trick at the end is what I should have started with to trick people to thinking
I had the entire display

It is almost ready to go, I just have to make sense of the source for others.
Last time I released a project, there were three different revisions of matching
hardware and software improvements with schematics,
and although others got it working, it caused confusion, and years of follow up for me.
Being mindful of that this time round, the schematic is in the PBP manual



The only differences are this is a 16F628A (instead of 16F84/A in the manual),
the LCD backlight is powered by the pic (RB6) for the strobe effect in the video,
and the pic is driven with an 8MHz crystal to match the speed in the video.
The clock speed is not critical though.
The serial Rx pin in the familiar looking diagram is not implemented.

If you make a board for this, it's still tentative.
LCD R/W pin may need to be accessed later, so it might pay to wire
it to somewhere accessible before wiring it to ground to mod later
(I heard you can rip all of the character graphics from the LCD itself).
It should also get a couple of buttons.
Cheers, Art.

[Demon]

WARNING: Video may trigger epyleptic seizure in some viewers.

Use 3D glasses under welding goggles as protection.



Awesome stuff Art.

Robert

[Art]

Here it is:
http://www.freewebs.com/defxev/LC2D.zip

Interestingly... I realised this is one of the two LCDs I bought off Melanie here ages ago:
http://www.picbasic.co.uk/forum/show...=2298#post2298
Funny that. There was not much fancier at the time, but now the options are endless.

I always get that last little nice feature working AFTER the distribution