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WVGA HDMI+VGA 8bpp Graphics Driver (works with the Parallax 7" HDMI LCD) in Spin2 — Parallax Forums

WVGA HDMI+VGA 8bpp Graphics Driver (works with the Parallax 7" HDMI LCD) in Spin2

RaymanRayman Posts: 12,676
edited 2020-12-13 22:48 in Propeller 2
I turned a little example from another thread into this graphics driver.
It's just a beginning of something but can do some things already.
It shows a splash screen and then some simple graphics.

This is in Spin2 and compiles with the Propeller Tool
(But, it's likely to be turned into FlexC shortly)

Update: I've fixed the circles and added text in the attached zip.
Update1c: Now with better line drawing routine from @dgately
Update2a: Now can do both either analog VGA or digital HDMI or both at the same time
Update3b: Now with mouse cursor and also moved basepin and cog settings to top level file. Demonstrates screen painting with mouse.

Note: You will likely have to edit the basepine settings (like "hdmi_base") in the HDMI driver (main file for Ver.3) to match the physical pins you are using for the HDMI adapter.


  • ColeyColey Posts: 1,101
    All working here! ;-)

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  • dgatelydgately Posts: 1,516
    edited 2020-12-08 23:51
    Thanks for this!

    Wikipedia sure helped with Bresenham's line algorithm for me (I used basically the same)

    Not getting DrawCircle() to work and DrawFilledCircle() works only partially:
    vid.DrawFilledCircle(vid.Red,vid.Blue, 600,300,80)   '(c,x,y,r) only the filled part is drawn
    vid.DrawCircle(vid.Black,600,300,79)   '(c,x,y,r) nothing gets drawn

    I had success earlier today with this to plot a circle's circumference:
    '' From:
    PUB PlotCircle(cx, cy, R,c)|x,y,xchange,ychange,radiusError
    	x := R
    	y := 0
    	xchange := 1 - 2 * R
    	ychange := 1
    	radiusError := 0
    		y += 1
    		radiusError += ychange
    		ychange += 2
    		if(2 * radiusError + xchange > 0)
    			x -= 1
    			radiusError += xchange
    			xchange += 2
    	while (x >= y)
    PRI Plot8CirclePoints(cx,cy,x,y,c)
    	SetPixel(cx+x, cy+y, c)		'' point in octant 1
    	SetPixel(cx-x, cy+y, c)		'' point in octant 4
    	SetPixel(cx-x, cy-y, c)		'' point in octant 5
    	SetPixel(cx+x, cy-y, c)		'' point in octant 8
    	SetPixel(cx+y, cy+x, c)		'' point in octant 2
    	SetPixel(cx-y, cy+x, c)		'' point in octant 3
    	SetPixel(cx-y, cy-x, c)		'' point in octant 6
    	SetPixel(cx+y, cy-x, c)		'' point in octant 7

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  • @Rayman Thanks for the new code. It is easier to understand because you have a separate LUT for the 24-bit colors. Given your example I'll try to put some 5x7 characters on the display. It took a while to figure out the color coding in an 8bpp bmp file and realize each bmp image has its own color table. Thank you. --Jon
  • RaymanRayman Posts: 12,676
    edited 2020-12-09 01:37
    Thanks for testing. I've fixed the circles and added a 8x16 font.

    The font looks a bit small on this screen...
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  • NOTE: Ensure you have the HDMI adapter connected to the P2 EVAL board's pin group that starts with 32 (32-39). @Rayman , can you note that in the top-line comments for the test program and the driver code? That info might help others get started without thinking these very-good programs don't work. Previous code had used pin group 48 (48-55). Remember, the 7-inch LCD requires an external +5V supply that can deliver at least one ampere. Thanks Ray. --Jon
  • RaymanRayman Posts: 12,676
    That's a good idea, I've added a note to the first post until then...
  • Ray,

    Possible issue with DrawLine() function...

    with "PUB Main()| cz":
    repeat cz from 0 to 32 step 2
        vid.DrawLine(200, 200, 200+cz * 2, 400, vid.Black)
    When lines are drawn with X parameters close together, line does not draw as expected (if they draw at all)
    My Spin2 PlotLine() code uses a pseudo-code example (from:
    PUB plotLine(x0, y0, x1, y1,c)
        if (abs(y1 - y0) < abs(x1 - x0))
            if (x0 > x1)
                plotLineLow(x1, y1, x0, y0,c)
                plotLineLow(x0, y0, x1, y1,c)
            if (y0 > y1)
                plotLineHigh(x1, y1, x0, y0,c)
                plotLineHigh(x0, y0, x1, y1,c)
    PRI plotLineLow(x0, y0, x1, y1,c)| x, yi, dx, dy, D
        dx := x1 - x0
        dy := y1 - y0
        yi := 1
        if (dy < 0)
            yi := -1
            dy := -dy
        D := 2 * dy - dx
        y := y0
        repeat x from x0 to x1
            if (D > 0)
                y := y + yi
                D := D + (2 * (dy - dx))
                D := D + 2*dy
    PRI plotLineHigh(x0, y0, x1, y1,c)| xi, x, y, dx, dy, D
        dx := x1 - x0
        dy := y1 - y0
        xi := 1
        if (dx < 0)
            xi := -1
            dx := -dx
        D := (2 * dx) - dy
        x := x0
        repeat y from y0 to y1
            if D > 0
                x := x + xi
                D := D + (2 * (dx - dy))
                D := D + 2*dx

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  • RaymanRayman Posts: 12,676
    Excellent! I can swap yours in.
    I didn’t actually test mine beyond that one line...
  • RaymanRayman Posts: 12,676
    @dgately Zip in top post now has your line drawing routine
  • I'm looking forward to experimenting with this code some! Thanks you all for making it possible!

  • Rayman wrote: »
    @dgately Zip in top post now has your line drawing routine
  • RaymanRayman Posts: 12,676
    I’m thinking about making this work for VGA too... Maybe either or both at same time...
  • Playing with drawing rounded rectangles... Need to add filled rounded rectangles, next.

    Drawing UI-type items (non-functioning):

    Converted (to spin2) this graphic drawing code from Cornell:
    PUB DrawRoundedRectangle(x,y,w,h,r,c)
      '' draw sides
    	DrawHorizontalLine(x+r ,y ,w-2*r, c) '' top
    	DrawHorizontalLine(x+r ,y+h-1, w-2*r, c) '' bottom
    	DrawLine(x, y+r, x, y+h-r, c) '' left
    	DrawLine(x+w-1, y+r, x+w-1, y+h-r,c) '' right
    	'' draw four corners
    	DrawCircleHelper(x+r, y+r, r, 1, c) '' top-left
    	DrawCircleHelper(x+w-r-1, y+r , r, 2, c) '' top-right
    	DrawCircleHelper(x+w-r-1, y+h-r-1, r, 4, c) " bottom-left
    	DrawCircleHelper(x+r ,y+h-r-1, r, 8, c) " bottom-right
    PUB DrawCircleHelper(x0, y0, r, corner, c)| f,ddF_x,ddF_y,x,y
    	f := 1 - r
    	ddF_x := 1
    	ddF_y := -2 * r
    	x := 0
    	y := r
    		if(f >= 0)
    			y -= 1
    			ddF_y += 2
    			f += ddF_y
    		x += 1
    		ddF_x += 2
    		f += ddF_x
    		if (corner & 4)
    			SetPixel(x0 + x, y0 + y, c)
    			SetPixel(x0 + y, y0 + x, c)
    		if (corner & 2)
    			SetPixel(x0 + x, y0 - y, c)
    			SetPixel(x0 + y, y0 - x, c)
    		if (corner & 8)
    			SetPixel(x0 - y, y0 + x, c)
    			SetPixel(x0 - x, y0 + y, c)
    		if (corner & 1)
    			SetPixel(x0 - y, y0 - x, c)
    			SetPixel(x0 - x, y0 - y, c)
    	while (x < y)

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  • RaymanRayman Posts: 12,676
    edited 2020-12-11 22:51
    I updated top post with a version that can also do regular VGA. Also cleaned up a bit.

    I can do HDMI and analog VGA output at the same time. Or, you can pick just one.
    Could probably do multiple HDMI and/or VGA at same time, but haven't tried that.

    Took some work to get the VGA driver to take the basepin as a parameter. Fortunately, could steal some of that from Chip's code.
  • RaymanRayman Posts: 12,676
    I've updated the top post with a new version that includes mouse with cursor.
    Demonstrates a Paint type app where you can draw on screen with mouse.

    Basepins and cogs all in top level file now.
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