Ok, its time for us Ubicom (Scenix) users to put this PIC video thing to rest... We alone have the speed required in a low cost micro controller to really make it happen!
Even at 50MHz on an Ubicom (Scenix) SX
(and the 100Mhz SX52's are working nicely), the 52uS video line on a standard
TV allows for up to 2600 instructions. At 40 columns that would be 65
instructions per column. 320 dots per line (8 dots per column) would allow
8 instructions per dot. Enough to be shifting out bits by rotating port A
interleaved with indexing a table and looking up the next character dot line
value? 256 dots per line would allow 10.
The lack of memory is the major limiting factor. With the 52 and about 200 bytes of RAM, we could try for a 40 character by 5 line display. Or 20 x 10. And if you are displaying only numbers... in BCD that is 400 digits. (...last 40 Caller ID numbers?, ...video paper tape for a calculator?, etc...)
And there is enough time (about 600 instructions) between lines to do some
unpacking of the next line...
...or reading in a new line from an external serial RAM
FRAM is $2.95 each for the 2kByte part
To generate character data for 128 characters, a 5 x 7 character matrix is
640 bytes of data in FLASH (hard to rotate though...). Or 1536 bytes with
a 8 x 12 matrix. Use IREAD so you won't have any problems with big tables.
Really only need 95 characters. The data is already done for you:
Here is the current "state of the art" in PIC video character generation.
In graphics, 200 bytes is only 1600 dots.. maybe 32 by 50 on the screen.
The gameboy is 160x144. It might be more interesting to make larger "sprites"
in FLASH instead of characters and work out a way to position them anywhere
on a 256 x 256 grid.
All of which pale in comparison to the #1 reason why this would be a cool thing to do...
...its a really neat HACK!
Also, I like CRT's better than LCD's... So...
I will pay $100, give away some SX's and do a big write-up on the site for the first person who can make a 20 character by 4 line NTSC output, standard Hitachi 44780 command (or RS232 or SPI or I2C or... anything useful) input, LCD replacement using an SX processor, some resistors, and the right code!
http://www.sxlist.com gets about 10,000 hits a day from 500 or so visitors (distinct IPs) and I will proclaim that you are an SX Master on every page for a week with a link to the full write-up of your accomplishment.
Now, if money is what motivates you, and the exposure doesn't bring you any new customers, you can re-write the code with what you learned (its always better the second time around), add the RS232 hardware and virtual peripheral and sell the unit.
Intelligent LCD controllers with 20 x 4 LCD's (and an RS232 input) cost better
than $100. Even if you don't already have a TV (or need a bigger display)
you can buy a 9" professional
video monitor for less than that or a
TV (no video input need RF modulator) for $39 or even a
unit (with CATV input) for $100 so you might have a Serial Backpack(tm)
killer. (Serial Packpack is a registered trademark of Scott Edwards
if you can get 40 x 4 it would replace the BPP440
Or build up some competition for bob:
jamesnewton at spamsxlist.com
SX FAQ: http://www.sxlist.com
NTSC Video signal specifications
Untested SX code for shifting out one pixel every other cycle from a character data table using the RA port as a 4 bit shift register
Nikolai Golovchenko's code snippet for detecting horizontal sync with the SX's built in analog comparitor
Character Set Data
Yves [rdd69415 at mail.telepac.pt] says
http://members.rotfl.com/JensJ/ some good software and information on sync generator and Pll etc...System PAL or NTSC Work with Microchip or Scenix ( Sx18 at 20 or 50 Mhz)
http://18.104.22.168/tom/theory/theory.htm (cached 20001213) this is a fantastic tutorial on how to detect sync in software.
Richard Ottosen says:
http://www.idcomm.com/personal/ottosen/ Look for the title "Display large characters on a graphic LCD" in the Stupid PIC Tricks section.
This was a project to test using the SX to put large characters on a graphic LCD which does not have a built-in intelligent controller. The display I used just has the shift registers that drive the pixels. The SX generates all the pixels continuously at a video rate to keep the LCD screen refreshed.
I put the schematic, some graphic LCD data sheets and several pictures on the page as well as the uncensored code. ;-)
[ed: well it's video, it's just not NTSC or PAL video...]
If you are an SXList member (see below) you can browse the discussion of this challenge on the PICList archives.
Eric Smith and Richard Ottosen have demonstrated thier SXList entry at the 6502 group meeting. Richard demonstrated the SX doing color and talked about the basics of TV video and how the hardware works. Eric demonstrated his SX created monochrome character display and talked about how his software works. Eric also talked about some of the subtleties of NTSC color. Hardware? Just the SX and an R/2R DAC. Check here to see for some pictures: http://www.brouhaha.com/~eric/ubicom/servid/.
George F Hotz s has single character generation and fadeing(!) working
The grapevine says that Wouter van Ooijen is hard at work on an entry as well!
Eric Smith and Richard Ottosen's SERVID entry clearly meets the contest requirements and bests any PIC design I've seen. It's an intellegent RS232 video terminal (4x20 character display) in one chip. See the write up here.. A trophy, some toys and $100 are on thier way to the winning team.
More information on SX Video generation at SX Video IO
...and now on to the next contest. SX FAST EMBEDDED ETHERNET - Now running. Are you ready to connect?
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<A HREF="http://www.sxlist.com/techref/scenix/contest/video.htm"> SCENIX VIDEO VIRTUAL PERIPHERAL - Design Challenge and Contest</A>
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