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| 1 | <HTML> |
| 2 | <TITLE> |
| 3 | UBB-VGA |
| 4 | </TITLE> |
| 5 | <BODY> |
| 6 | |
| 7 | <H1>UBB-VGA</H1> |
| 8 | |
| 9 | This is an effort to use the |
| 10 | <A href="http://en.qi-hardware.com/wiki/UBB">UBB</A> |
| 11 | (Universal Breakout Board), a few resistors, and a VGA cable to create a |
| 12 | workable VGA signal on the |
| 13 | <A href="http://en.qi-hardware.com/wiki/Ben_NanoNote">Ben NanoNote</A>. |
| 14 | |
| 15 | |
| 16 | <H2>What it can do</H2> |
| 17 | |
| 18 | The video signal timing is controlled mostly by software. Available |
| 19 | resolutions include 640x480 and 800x600. |
| 20 | At present, the maximum resolution is 1024x768 with a refresh rate of 50 Hz: |
| 21 | <P> |
| 22 | <A href="ubb-vga-pub-1024-medium.jpg"><IMG src="ubb-vga-pub-1024-small.jpg"></A> |
| 23 | <P> |
| 24 | The 16 colors are generated from a binary channel for red, green, and blue |
| 25 | each, plus a binary luminance channel that affects all three color channels. |
| 26 | |
| 27 | |
| 28 | <H2>The hardware</H2> |
| 29 | |
| 30 | The current design is based on the |
| 31 | <A href="http://en.qi-hardware.com/wiki/UBB">Universal Breakout Board</A> (UBB) |
| 32 | that plugs into the Ben's |
| 33 | <A href="http://lists.en.qi-hardware.com/pipermail/discussion/2011-January/006908.html">8:10 card</A> |
| 34 | slot. The MMC controller in the Ben's Jz4720 CPU is tricked into |
| 35 | considering the UBB-VGA board as a MMC/SD device and streams the pixel |
| 36 | data at a rate of up to 56 MHz. |
| 37 | <P> |
| 38 | The pictures below show a prototype that connects directly to a VGA cable: |
| 39 | </P> |
| 40 | <A href="ubb-vga-pub-plugged-medium.jpg"><IMG src="ubb-vga-pub-plugged-small.jpg"></A> |
| 41 | |
| 42 | <A href="ubb-vga-pub-v2-medium.jpg"><IMG src="ubb-vga-pub-v2-small.jpg"></A> |
| 43 | <P> |
| 44 | The circuit is very simple. In its most basic form, it consists of UBB, |
| 45 | ten resistors, and the VGA cable: |
| 46 | <P> |
| 47 | <A href="ubb-vga-schem.png"><IMG src="ubb-vga-schem-small.png"></A> |
| 48 | <P> |
| 49 | Each of the three analog color channels uses three resistors for lowering |
| 50 | the 3.3 V logic voltage to the 0.7 V analog VGA level and for mixing in the |
| 51 | luminance (Y) signal. The tenth resistor pulls down the HSYNC/CMD |
| 52 | line, to fake the response the MMC controller expects to receive |
| 53 | from a MMC device when starting a block write. |
| 54 | |
| 55 | |
| 56 | <H2>The software</H2> |
| 57 | |
| 58 | The driver currently runs in user space (with a lot of dirty tricks) and |
| 59 | blocks all other system activity while running. |
| 60 | It can display the test image shown above, the content of the LCD display, |
| 61 | or a PPM image. |
| 62 | The source code can be found |
| 63 | <A href="http://projects.qi-hardware.com/index.php/p/ben-blinkenlights/source/tree/master/ubb-vga">here</A>. |
| 64 | |
| 65 | |
| 66 | <H2>Mailing list, IRC</H2> |
| 67 | |
| 68 | Development discussions and such happen on the |
| 69 | <A href="http://lists.en.qi-hardware.com/mailman/listinfo/discussion"> |
| 70 | qi-hardware mailing list</A> and on the |
| 71 | <A href="http://webchat.freenode.net/?randomnick=1&channels=qi-hardware">#qi-hardware |
| 72 | channel</A> on |
| 73 | <A href="http://freenode.net/">freenode</A>. |
| 74 | |
| 75 | <P> |
| 76 | <HR> |
| 77 | Last update: 2011-05-07 <I>Werner Almesberger</I> |
| 78 | <HR> |
| 79 | </BODY> |
| 80 | </HTML> |
| 81 |
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