video output from SX

Nate

Howdy folks,

I've been writing command/control aplications with the SX28 for about a year now, and my aplications are getting complecated enough that I need a more sophisticated means to interface with humans than LED's, 7-segment displays, and small LCD displays.

I was thinking about using Visual Basic and a RS-232 connection for interfacing, but this would require a computer for each SX application.· I have noticed the XGameStation and was wondering if this·would be·a simple and small way of interfacing a SX to a mouse and video display.· I am hoping that it can teach me the basics of video interfacing, and I could perhaps then construct my own simplified version of it to allow somewhat sophisticated interfacing with a SX application.· Has anyone bought a XgameStation and used it?· Could one use it to create sophisticatd video output (ie radio buttons, sliders, gauges?).

I have also looked at the xGameStation site, and the video samples there look like they have pretty low resolution.· Are the monitors (TVs) used by the xGameStation inherently different (low res?)·than a computer monitor?· I was hoping the xGameStation might make it possible to create forms similar to Visual Basic on a flatpanel LCD without the overhead of a computer.· Anyone have any input?

Nate

allanlane5

1. Yes, quite a few people have purchased the XGameStation since December 2004.

2. The XGameStation uses very simple hardware to do its video -- I believe the SX is generating HorizSync, VertSync, and all the little bits in between. Thus your resolution is limited to what the SX can fetch and do.

3. I don't know what resolution the XGameStation supports this way. I've heard it compared to the Atari 2600 -- but I hope it's a little better than that.

Paul Baker

In essence yes the SX can do what your requesting, there are some caviats though. The XGamestation represents the near limit of what an SX is capable of as far as video resolution. That means your going to get Atari 2600 like video quality. Generation of color television is a stretch for the SX, here is a site where a guy got the SX to display color with just an SX http://www.rickard.gunee.com/projects/video/sx/tetris.php·you'll note that he has limited ability of changing the color quickly and he uses a very specialized frequency to run the SX at. The Xgamestation achieves its color television performance by using an additional helper chip to generate the color data rather than placing the burden on the SX.

Now if your talking about driving a VGA monitor, this is a less explored path. For standard VGA (640x480) that is 307200 pixels per frame, at full 24 bit color, thats 7.3728 Million bits of data, assuming you are using 8 lines of data to push the information out, thats 921,600 bytes of data, running at full tilt, that would allow a maximum refresh rate of 54 Hz. If you chose a refresh rate of 27Hz, that would mean pushing out a byte of data every other clock cycle. Since you need to store all this information somewhere off chip, your not going to get this data rate. But using a limited color palette, such as 256 colors you'll stretch the requirement to a byte of data pushed every 6th cycle, and this is more resonable. But this leads to no processing time availible to perform other tasks such as reading mouse movements and updating display contents.

Now you could get better results if you used a dual port SRAM and two SXs, one whose sole responsibility is to drive the monitor and the other whose function is to take inputs, and update the display accordingly.

You seem to have a little confusion between a monitor and a television, the Xgamestation is using a television to display the data not a computer monitor. Television has limited resolution and VGA graphics looks fuzzy and ill defined on it, this is true even with PC video cards that have a television out. This is borne from the limitations of the NTSC standard not the computer processing power.

Post Edited (Paul Baker) : 4/1/2005 8:51:52 PM GMT

Bean

Nate,
Check out my SX-Video module. It is open-source, the schematic and source code is freely available. It's on my tag line.
Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video Display Module" Available Now.

www.sxvm.com

"A problem well defined, is a problem·half solved."
·

Nate

Terry, Paul and Allan,

Thanks for the responses.·

Terry - I have looked at the SX-Video module - excellent job in the contest by the way.· It appears that the module may be somewhat limiting for me - I would like to output text and graphics - I'm really trying to emulate the Visual Basic forms without the overhead of a computer or being beholden to MS.

I will admidt that I don't really understand why a TV CRT monitor·has a more limited resolution than a VGA monitor (CRT type).· I am assuming from my (limited) general knowledge that a TV monitor produces a picture by sweeping an e-gun, which is controlled by an analog signal.· If a VGA monitor (CRT type) also uses a swept e-gun, directed by a digital matrix, how can the VGA resolution be better?

In any case, I think I am leaning toward using a VGA type monitor to display my SX data.· Does anyone have any good reference sites on what a VGA monitor needs for a input signal?· I am guessing that a video card, such as found in computers, creates·and·outputs these digital matrixes to the monitor - if this is the case, what exactly·do the video cards themselves need for input?· Do you just send them information on the pixels that are changing?· Before I get jumped on for not doing a Google search, I will do that but·often people in this forum have ideas that can help sort the wheat from the chaff.

Nate

Paul Baker

http://www.networktechinc.com/technote.html

http://www.epanorama.net/documents/pc/vga_timing.html
http://www.cs.unc.edu/~stewart/comp290-ghw/vga2.html

http://www.xess.com/ho03000.html
·