Video output for microcontroller 2

[blcpro]

Hello all,

I was interested in having video (VGA-type) output capability added to some of my 8 or 32-bit microcontroller designs. I've spent the last few days looking around and doing research but I'm not coming up with anything useful. Basically, I'm looking for the controller chip which sits between a MCU parallel bus and the VGA-type connector of a standard monitor. Obviously, I don't have any experience with the video interface or I'd know what I'm looking for. Just for refernce, the types of MCU's I use are PIC, Hitachi SH2, ARM, 8051, etc. These all have your basic 8 or 32-bit data buses available.

Anyone have some ideas where to start?

 

[itsmoked]

I would suggest you look at "Circuit Cellar" magazine. Especially previous issues going back a year or two. There is always someone crazy enough to want to do this and I think I have seen four or five how-to articles on just exactly that.

You may need to buy one of their 'umpteen' issues on a CD.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[davesaudio]

IMHO
A single chip solution is unlikely. There is a reason video cards cost and are as complex as they are.
Unless you learn vhdl/verilog and program an fpga etc.

I think this is about the simplest

http://www.dontronics-shop.com/home.php?cat=262

The obsolete motorola 6845 might have got you there
I don't recall what it need in the way of glue chips...

If you are using an ARM it should have enough horsepower
to generate the RGB directly, No?

 

[MikeHalloran]

That's a pretty ambitious idea. You might wish to review an original IBM PC BIOS listing to see what it went through just to generate CGA characters on the screen.

Just to screw around with it, I might plug a cheap VGA board into a passive backplane, and drive the PC bus signals (slowly) with addressable latches. I don't think I'd even try to adapt the MCU bus to drive the PC bus directly.



Mike Halloran
Pembroke Pines, FL, USA

 

[Warpspeed]

Agree with davesaudio.

Basically it sounds like you just need a bog standard VGA video card. Each pixel location will be memory mapped, and video attributes entered directly from the MCU bus. The whole ram area is repetitively read to create continuous RGB video outputs, along with appropriate syncs and blanking. No point in reinventing the wheel. These cards are now so cheap as to make any other solution impractical and uneconomic.

All you need is address and data bus, read/write strobes and some power. Just treat it like an ordinary basic static ram card, and away you go.

 

[Madcow]

I have planned to try this circuit sometime, but
never had the time.

http://yusoft.kulichki.com/english/pic/my_proj.htm

 

[MacGyverS2000]

Mad, I worked with a similar project a few years back. The main problem with it was the PIC was unable to spend time doing anything else but video as timing with the ISRs was exact (using NOPs and such to pad out specific routines). It did the job it was originally intended to do (display a graphic on the screen), but dynamic graphics was an impossibility with that particular design.

Curious to make another attempt at it some day, but that's a long way off.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

"PIC....unable....anything else but video"

Reminds me of the Timex Sinclair 1000 (aka ZX81) toy computer circa 1982. If you wanted it to actually accomplish anything, you had the option to turn off the SW-driven video.

Here's a link for laughs:

http://en.wikipedia.org/wiki/Sinclair_ZX81

 

[MacGyverS2000]

Ahhh, fond memories... I picked up a Sinclair 1000 from neighbors across the street, had some real success creating games for it. I wanted to sell them to others, but didn't know a single other person who owned a 1000. The zig-zag pattern on the screen while a tape was loading told me whether or not a program was actually loading... if I had the tape flipped over to the wrong side, or some other such nonsense, I could tell from the screen pattern. For about $60 I picked up the computer, a 16k expansion pack, the "thermal" printer, and 5 or 6 rolls of "thermal" paper.

I used that for about a year and a half, when new neighbors moved in across the street. They brought along a Spectrum, which I purchased for $40(?). Then my games had color!

Great little machines, but the keyboard on the 1000 was a PITA... tough to type on, you had to be very deliberate in your keypresses. Surprised I didn't wear out the backspace key.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[Madcow]

PIC's can do vidio, you just need a bunch of them.

I was thinking of using one Pic for each color.Then
use another processor to talk to all 3 on the SPI bus.
Then I realized that I would probably run out of ram.

I think blcpro wants something like the Epson chip.
They have versions with onboard memory.

Epson vidio chip to TI processor.

http://focus.ti.com/lit/an/spra847/spra847.pdf

Ti also has a few Micros/dsps that have a vidio port.

If you want to do a fpga or asic.

http://www.opencores.org/projects.cgi/web/vga_lcd/overview

 

[itsmoked]

The Sinclaire 1000... Yeeeeaaaah..

http://oldcomputers.net/index.html

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Madcow]

I'm more a TRaSh-80 fan.
Now that was graphics.

 

[analogkid2digitalman]

Is that the 16K expansion pack on the back? I had one of those back in the day, my first 'PC'.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[blcpro]

Thanks everyone for your input... I'll check out the links offered. I was away for a few days... anyway, it sounds like a vga card might be the simplest way, although not practical for a space-confined design. Maybe there are video card modules out there? Something small and easy to interface? I havn't heard of any, but I will begin a search.

 

[blcpro]

oops, looks like thats exactly what davesaudio found for me... hehe.. he gets a star.

 

[felixc]

yeah, davesaudio found a nice and inexpensive product!

 

[utimgr]

I have a unit..has a FPGA onboard, drives out text VGA. Are you looking for graphics or just DOS-like text display?? It can do really basic graphics if needed.

Essentially a serial input, and VGA output.

 

[blcpro]

just looking for the basics at the moment, but maybe more complex graphics later on... what do you have?

 

[utimgr]

http://www.dontronics-shop.com/home.php?cat=262

simple serial interaface, I drove it from a PIC18F part

 

[davesaudio]

where have I seen that before?

http://www.dontronics-shop.com/home.php?cat=262

hmm...