PIC TV out

Peepsalot · Apr 13, 2006

I have seen a couple examples on the internet of PICs being used to output to a TV display(PICdream for one).

I couldn't tell from the schematics exactly how this output works. I would assume it is just the video part of component input(RCA plugs). My question is if it is possible for a PIC to make signals for standard coax cable. I would guess it's not capable of the frequencies involved, but i have no idea how that works. Does someone know how NTSC video signal on RCA differs from what comes through the coax? How are channels differentiated? How is sound mixed into the same signal? Is it possible to send the same signal to all channels?

My idea is a tiny gag device that you could plug directly to the back of a tv and just have it display a single prewritten image. The goal would be to make the circuit as simple and small as possible.

upand_at_them · Apr 13, 2006

I'm not sure what you mean by the "signal through coax", because you can have any signal run through a coaxial cable. Google "pic pong", though, and you'll see examples of generating NTSC signals with a PIC to be displayed on a TV.

Mike

Peepsalot · Apr 13, 2006

I mean like a regular TV coaxial cable, I don't know any other words for it. The kind that a cable company would use to send all your 100something channels over. As opposed to RCA that splits up audio, and video, and is only one channel.

I don't know all the correct terminology for the signal types, that's why I'm trying to describe them by their connectors. I am aware that you can send any type of signal over any wire, but can you just assume for this situation that the cables/connectors I am referring to are carrying whatever type of signal would normally be used when a US citizen connects such a connector to their televison?

kjennejohn · Apr 13, 2006

You say...you wan' video?

The cable stuff will never come out of a PIC. The frequency is higher than the PIC's clock, for openers.

However, you can do plain jane NTSC, as it is 15.7kHz (why doesn't that sound right?). There are PIC-centric video boards for $30 to $100 that can do both video and audio. One can even use game controllers. However, you have to squeeze out every CPU clock to achieve this. Mostly these do 192 characters to a standard monitor, usually monochrome, but there is one called the BOB-3 that will do 40x17, which is 680 characters! It supports a ROM with 256 characters. All these boards allow some insertion of user-created characters.

Here's the site for the BOB-3:
http://www.decadenet.com/bob3/bob3.html

Check Parallax.com for this game developer's board system:
**broken link removed**

Here's a low res video module from Parallax:
http://www.parallax.com/detail.asp?product_id=30012

Ah, nuts! The most interesting OSD for the money has been discontinued!

And check Basicmicro(.com) for their PIC video board. It is a simple generator (12x16); it doesn't do On Screen Display. It's not terribly well supported, but there is (buggy) code to modify to use it. Check the Atom Hardware forums about this device.

And now you know everything I know on the subject.
kenjj

kjennejohn · Apr 13, 2006

Hmmm. I've used the features before on other forums li...agic handshake to get these to work? kenjj

Nigel Goodwin · Apr 14, 2006

kjennejohn said:
Hmmm. I've used the features before on other forums li...n, like this [url]http://www.winpicprog.co.uk.

As for the thread, you need a VHF or UHF modulator, that converts the video signal to a suitable modulated RF signal.

However, it appears you want a 'picture', you can't do that with a PIC, far too little memory and not fast enough.

Peepsalot · Apr 14, 2006

Nigel Goodwin said:
As for the thread, you need a VHF or UHF modulator, that converts the video signal to a suitable modulated RF signal.

However, it appears you want a 'picture', you can't do that with a PIC, far too little memory and not fast enough.

An incredibly pixelated picture is still a picture in my book

Just anything you could use to put a pattern or message on the screen with.

Nigel Goodwin · Apr 14, 2006

Peepsalot said:
Nigel Goodwin said:

As for the thread, you need a VHF or UHF modulator, that converts the video signal to a suitable modulated RF signal.

However, it appears you want a 'picture', you can't do that with a PIC, far too little memory and not fast enough.

Click to expand...

An incredibly pixelated picture is still a picture in my book Just anything you could use to put a pattern or message on the screen with.

You can do simple text or patterns, but by 'image' I presumed you wanted an actual 'picture' of some kind.

To convert from video to RF use a modulator from an old VCR, they accept a fairly normal 1V p-p.

upand_at_them · Apr 14, 2006

Nigel Goodwin said:
To convert from video to RF use a modulator from an old VCR, they accept a fairly normal 1V p-p.

And you don't even have to remove it from the VCR. To test the circuit you can run the signal through the VCR and then to the TV.

Mike

cyb0rg777 · Apr 22, 2006

Just to add to the conversation here is a good link.
**broken link removed**
You can make games like pong and tetris.
I've never tried them but they been around a few years.
Very nice work IMO.

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PIC TV out

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