Composite video with MSP430 chip

[NatureTM] used part of the Thanksgiving holiday to get composite video output working with an MSP430 microcontroller. He’s using one of the chips that came with the TI Launchpad, which is a big hardware limitation because of the relatively small code memory and RAM. The chip displays one still image at a resolution of 192×40 pixels. Still, this is a great way to learn about composite video signals, as a lot of other projects use a TVout library to save you the headaches. All you’ll need is a TI Launchpad, a 16 MHz crystal oscillator, two resistors, and an RCA jack. Dig through the code and see what a great job [NatureTM] did of offloading as much work onto the chip’s peripherals as possible.

Comments

  1. st2000 says:

    Wow, you got all that into a TI launch pad? No cheating? I’ve two of those just sitting here loosing value as we speak. No wonder they haven’t shipping my TI robot – they’re waiting to see if it’s worth the trouble. They didn’t ship it to you did they?

    -nice

  2. dave says:

    Awesome. That’s TRS-80 model 1 resolution

  3. bluehash says:

    Congrats NTM!

  4. gatesphere says:

    Nice job, NTM.

    I don’t see you on #43oh right now though… I’m guessing class. :P

  5. lamer says:

    i would like to see the launchpad
    used to make Text overlay,

  6. NatureTM says:

    Thanks HaD!

    @st2000
    No, they didn’t ship my evalbot either. I did consider putting the TI logo next to the phrase, “Where’s my evalbot?” for the demo image. It’ll come soon.

  7. zool says:

    cool, 192×40, does that mean you could have multiple screens or a video/sprites at even smaller resolution?

  8. jbremnant says:

    great job! nice to see this getting posted here.
    it’d be nice to see pong running using your lib.

  9. localroger says:

    Wow, it’s like a single chip COSMAC Super Elf.

  10. sp00nix says:

    This made me finally open and assembly my launchpad, and i have no idea where to get started and get this onto the damn thing. I have all the software installed and the source loaded but after that i’m lost.

  11. bluehash says:

    @sp00nix try here for a list of projects for the Launchpad: http://www.43oh.com/forum/viewforum.php?f=9&sid=674ff4ea9685e5e9aa1a29aebb1f7fc5

  12. vtl says:

    Wow, people actually got their launchpad? I ordered mine 19th september and still never got it. Estimated ship date was over a month ago and the order status just sits there at ‘processing’.

  13. Richard says:

    If its not colour, its not a composite video signal, since composite is the result from adding chroma and luma together. Its just a monochrome video signal.

    While this is a nice hack and all that, I really do question the use of outputting an obsoleted video format on a microcontroller when it takes so much of its resources that you have virtually nothing left in it.

    There is a void between these hacks and something like a beagleboard with a proper video out generator that is awaiting a product, but IMO analog SD video like these and the chumby make have no place these days other than curious.

  14. Andrew says:

    Nice project!

    @Richard
    If its not in glorious color whats the point, eh? Never mind the fact this project shows a ton of very useful theory behind how video signals are created.

  15. bluehash says:

    @Richard, You don’t get to go this low on the Beagleboad, plus this was a great learning project on how video signals work. Best of all, he got it too work using the chip’s hardware.

  16. NatureTM says:

    Hey Richard, I thought of the fact that it’s not real composite, since it’s missing hue and saturation. I considered calling it “composite” with quotes every time, or “composite minus color.” I decided that the signal did contain brightness, sync, and blanking, so it was sort of a composite signal. It also does adhere to the NTSC composite standard. Think of it as a composite signal that’s only in B/W.

    I used this “obsolete” video format because every TV, including very modern ones, have a composite input. It may be obsolete, but it’s still universal.

  17. st2000 says:

    @vtl:

    I think I was lucky. I ordered 2 direct from TI and got them. Someone at work ordered 2 as well. But he did so from DigiKey. He got those but had to pay shipping. If you really need one now you might try DigiKey. I am sure we and TI are working in a “far from consumer production supply chain” scenario and can expect a wide range of lead times.

    @Richard

    Hum, but the black and white signal does contain 1) vertical sync, 2) horizontal sync & 3) brightness. For many years that was all there was. Color came later and had to be added in such a way as to not disturb legacy equipment. I wasn’t around but assume, never the less, it did. As the color is a phase modulated signal added to everything else at about 3.8MHz, the black and white sets were probably sensitive to that signal as the brightness was able to be modulated all the way up to about 4MHz. So watching a color signal on an old black and white set probably added an annoying cheese grader pattern to everything. In the end, I’d still consider the output of this project to be composite video.

    @NatureTM

    If you wanted to add color, you might think about using s-video. I’m not sure exactly how it works, but Sony split the video (I’m going to call it) B&W composite from the color so as to preserve the higher bandwidth of the B&W composite signal. This plays right into how a VCR works and why Sony had such a better picture when used with VCRs. This way you don’t have to mix in yet another signal. Regardless I believe you sill have to add a color xtal (common as dirt I suspect) and some way to control the delay to simulate phase modulation (maybe just switching in and out extra gates?). Yes, you might be able to do it in software on a fast embedded processor. You would need to be able to move a 3.8MHz wave fractions of a wave cycle back and forth. So the processor would have to be moving several multiples of that. Say 64MHz, 128MHz or 256MHz depending on how many instructions you can get from one machine cycle.

    -good luck

  18. st2000 says:

    Of course I meant cheese grater, not grader.

  19. localroger says:

    @NatureTM, why not just say it puts out NTSC video? I think that’s what Parallax says about the Propeller (and they even do put out true composite with color, since the chip has special hardware to generate the color subcarrier).

    @st2000 I have actually watched color TV broadcasts on a legacy TV that wasn’t designed for them (and built with vacuum tubes sometime around 1964), and there were no visible artifacts from the color signal. I don’t think those TV’s actually passed signals up to 4 MHz. In any case it was all very carefully designed to make sure those old sets worked OK, which is one reason the signal format is such an odd hack.

  20. Mark says:

    “Wow, people actually got their launchpad?” -VTL

    “I am sure we and TI are working in a “far from consumer production supply chain” scenario and can expect a wide range of lead times.” -st2000

    I am in the same boat as VTL. From what I understand TI has made a name for themselves catering to smaller manufacturers. By screwing up the logistics of something like this says they don’t really cater to smaller markets. If your not going to do it right then they should have not bothered. For those that say that TI is not really to blame…. If McDonalds decided that they didn’t have the $$ to pay out the million dollar winner of their Monopoly game there would be Hell to pay. They got the benefit from the excitement generated from the game, then they should be able to pay out.

  21. st2000 says:

    @Marl

    If you take a look around everyone is trying to gain a following. I think Microchip is currently taking 20% off of their kits (hint hint, I’d like a touch switch development board for Christmas). I think ST Micro is currently running a contest and might be selling their development board at a low price. And TI is just doing the same. Actually it is all a big win for us hackers who buy in small quantity.

    On top of that, everyone has reduced their inventory. Face it, no one can afford millions of dollars of capital sitting around doing nothing these days. Even if you wanted 10,000 brand new processors, I think Microchip lead times are such that their more popular processors are not immediately available for the asking.

    BTW, I don’t play the McDonalds games ever since they screwed it up:

    http://en.wikipedia.org/wiki/McDonald%27s_Monopoly#Fraud

    …so, in the end, I guess you *are* right.

    (I can’t resist): “All your LAUNCHPAD are belong to us!”

    …in case I parted your hair:

    http://en.wikipedia.org/wiki/All_your_base_are_belong_to_us

    …lord, at this rate, I think I owe Wikipedia money:

    http://wikimediafoundation.org/wiki/WMFSA001/en/US?utm_medium=sitenotice&utm_campaign=20101203EA012&utm_source=20101203_EA004A_US&country_code=US

    -I’m sure your launchpad is getting closer and closer.

  22. Mark says:

    TI is listening in…..

    Last night I received notification that my order was shipped. Cool beans, a 4 or 5 month wait but I will take it. I guess I will have to stop saying bad things about TI.

  23. vtl says:

    Just to follow up, I replied to the order confirmation saying that it was taking forever and the email bounced back. But the very next day I got a confirmation that it was shipped and I got the package today (3 month total wait).

    If you want an MSP430 quickly you can just order the free samples, mine arrived in less than a week. Only downside is not having a board.

  24. simonbaker says:

    I love it — superb example of desert island programming — what can be done when you think it should be impossible. Nice, and instructive.

    For practical projects, I’m interested in the MSP430/DSP combos too.

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