Thursday, December 13, 2012

NTSC TV Interface (PIC12F1840)

UPDATE 12.1231:
As you may know, the preliminary work on video from the PIC led to creating of a PONG game. Well, that game has led to a LOT of work done on the NTSC interface. And as part of that work, I split out all of the NTSC stuff into it's own module - NTSC_Interface.INC and NTSC_Interface.ASM. Hopefully this makes for easier implementation of NTSC video in your projects. I also have ODD/EVEN fields implemented and the timings are _really_ tweaked to try to meet spec. The big LCD TV is working better (VSync locks now, data is clean, but there's a weird shifting of the line data), and everything else I have thrown at it works great, including my Sony LCD goggles.

I am including the full PONG game so you can see how the NTSC_Interface module was integrated into the game itself - and hopefully it will be a learning example so you can implement NTSC video into your own PIC project.

RELEASE V4.04:
PONG.ASM (V4.04): http://pastebin.com/Wbxbg94R
Common.INC (V1.10): http://pastebin.com/rMJcnLqt
NTSC_Interface.ASM (V1.00): http://pastebin.com/aPi9eKRJ
NTSC_Interface.INC (V1.00): http://pastebin.com/nXCannBS

Enjoy - and Happy New Year!

UPDATE 12.1220:
Thanks to helpful readers - I know have a method to post source code.

The main program (Video_Game.ASM): http://pastebin.com/Jc5k3G0m
A common file I drop in all projects (Common.INC): http://pastebin.com/PEmji9VG

Let me know if that gives you any problems.

UPDATE 12.1214:
We have a bouncing ball! I am updating the video buffer during the vertical sync.


video

UPDATE 12.1213:
Data retrieval from the EEPROM is working now. It also simplifies the code quite a bit. I put a monochrome (1 bit - black or white) 32x32 picture of my son in the EEPROM and this is how it looks. Nice! Pixelicious, but nice!


Original post after the break.



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Another night, another quickie project. This is an NTSC TV Interface, using the PIC12F1840. The hardware is simple - two resistors (1K ohm and 470 ohm), a PIC12F1840, a RCA composite video connector - and that's it.

It's only NTSC because that is how I programmed the timing. If you want PAL or SECAM, you will have to research the timing and incorporate those timings into the program.

For NTSC - 512 lines, interlaced. Each line has a 4us hsync (low) and then 60us of data. The vsync pulse is 60us low, then 4us high. So - vsync pulse, then 256 lines (hsync pulse then data), then another vsync, then the last 256 lines. Lather, rinse, repeat.

Timings are CRITICAL. You want each line of equal length. A 4us hsync, then 60us of data, then another hsync, then _58_us of data will cause jitter. If you get the timing right, the display locks in very nicely to the signal.

My target composite video device is a Sony PS1 LCD display. Running the PIC at 32Mhz, I can get theoretically get a 32 bit x 512 line display. Yeah, not great, but you _can_ do something with it. Just look at the pic.

Right now I am working on retrieving the video data from the EEPROM. There's enough space for 64 lines (32x64 display) - or, I may split it into 2 video pages (32x32 display, 2 pages). That's enough to do some blocky graphics.

All in all, a very interesting night. I haven't dealt with composite video (with horizonal and vertical sync, front porch, back porch, etc.) in a long time - not since my CMX/Orrox days.






4 comments:

  1. Nicely done, Timothy. Can you share any software at this time, Sir?

    Happy Holidays...

    ReplyDelete
  2. Thank you, Sir!

    What is the best way to post a large chunk of source code to blogger? I don't want to just create a new post and drop the whole mess into it.

    Merry Christmas and Happy Royal Plowing Day to you!!!

    ReplyDelete
  3. you could drop code into pastebin
    or equivalent ?
    e.g. http://pastebin.com/
    http://pastie.org/
    http://snipt.org/
    http://safebin.net/
    http://codepad.org/

    ReplyDelete
  4. Yes! Thank you. It will be posted as an update to this post (at the top) shortly.

    Thanks again!

    ReplyDelete