If my screen has RGB inputs do I need the AD725?

[nubie]

My plan for this is a handheld system of the sort at Benheck.com, I already have a Radica Sega Genesis TV game PCB installed in an audiovox screen with buttons added to the face: http://forums.benheck.com/viewtopic.php?p=277857

The chip in the Audiovox screen is a Sharp IR3Y31M that supports RGB inputs, does this mean that I don't need the RGB -> Composite chip? (currently the most expensive single chip in this project)

I have the PDF for the chip, it is about 3.5MB. The only part I am unsure of is the 4FSC pin, the Sharp does have Sync In and RGB pins.

I can save $11.54 and SMD soldering (well I will be soldering onto the SMD Sharp chip, but it saves me 10-11 pins worth.)

[havok1919]

The chip in the Audiovox screen is a Sharp IR3Y31M that supports RGB inputs, does this mean that I don't need the RGB -> Composite chip? (currently the most expensive single chip in this project)

I have the PDF for the chip, it is about 3.5MB. The only part I am unsure of is the 4FSC pin, the Sharp does have Sync In and RGB pins.

I'd say that would "probably" work. If the chip is expecting 'standard resolution' (aka, CGA/NTSC ~15.75KHz sync rate) RGB like for SCART with separate composite sync it'll probably work. You might need to change the value of the pulldown resistors on the R2R DAC (the video resistor networks on PORTC) to adjust the level of the signals going in. (With the 75ohm resistors it's set to do about 0.7V peak to peak which might be a little too hot for the LCD. You could try something like 68ohm if the display is too bright and/or if you get color smearing. If it's too dark, try something like 100ohm and the output voltage will go up.)

The 4FSC is just a colorburst clock for the NTSC encoder, so you can ignore that. You might need to scale the output voltage on the csync line-- I don't know what levels the Sharp part is expecting. (Just want to be sure it can handle a ~5V 'logic level' sync input.)

RGB should look really good since you won't get into 'out of bounds' color saturation zones like with an NTSC encoder. If you can post a link to the PDF or something I'd give it a once-over for you just to be safe.

If the chip was expecting only "VGA speed" sync signals on the RGB input then it might not be able to get down to the 15.75KHz horizontal sync rate, but in that case they usually have two sync inputs (Hsync and Vsync), so if it only has Csync that's promising.

-Clay

[nubie]

Thanks Clay

Here is the link to the PDF: http://www.lcdvision.com/download/inter ... R3Y31M.pdf

Here are some pretty good macro shots of the board I am using:

http://picasaweb.google.com/nubie07/Aud ... 2591676498

http://picasaweb.google.com/nubie07/Aud ... 4853485666

I don't know about a sync now that I check those pictures, it may want to see the sync on the green line.

Mouser has a DIP-20 NTE879 RGB-PAL/NTSC encoder, part # 526-NTE879 I wonder if that would work for a standard circuit (at $6.39 it sure beats $11.54 + $9 adapter on the AD725 when making a through-hole board, if it works).

Out of curiosity, you mentioned a simpler DAC resistor network, I assume your values were for the Red and Green pins, what would you use for the Blue bits?

Edit: I see now that you put it in the text under the picture, I take it 806 and 1.58k are the correct values for Blue.

[havok1919]

Here is the link to the PDF: http://www.lcdvision.com/download/inter ... R3Y31M.pdf

I have a nagging suspicion that that won't actually work. I believe that the RGB inputs in question are digital (color on/color off). Probably they'd normally be used for some kind of video overlay on the screen. (Volume control, etc.) You can try it, but I kinda suspect it won't work.

Mouser has a DIP-20 NTE879 RGB-PAL/NTSC encoder, part # 526-NTE879 I wonder if that would work for a standard circuit (at $6.39 it sure beats $11.54 + $9 adapter on the AD725 when making a through-hole board, if it works).

I don't know that one off the top of my head... The problem with some of those older parts is that they can require a small army of weird caps and inductors to function. One other option-- locate an old Playstation 1 or Sega Genesis at goodwill/fleabay/etc. They'll have an RGB->NTSC converter in them. If you buy an otherwise dead system they can be pretty cheap. The PS1's used the Sony CXA2075 which is really nice. (great picture quality) Unfortunately that picture quality came at a price-- namely about 3/4W power consumption!

Out of curiosity, you mentioned a simpler DAC resistor network, I assume your values were for the Red and Green pins, what would you use for the Blue bits?

Edit: I see now that you put it in the text under the picture, I take it 806 and 1.58k are the correct values for Blue.

Yep, that just cuts the parts count down and allows for balanced color (leave the LSB of red and green 'off' and the MSB's of RGB then track 1:1) and you should get good grays free of tint.

-Clay

[nubie]

I have a nagging suspicion that that won't actually work. I believe that the RGB inputs in question are digital (color on/color off). Probably they'd normally be used for some kind of video overlay on the screen. (Volume control, etc.) You can try it, but I kinda suspect it won't work.

I have confirmation on the Benheck forums, where they run a lot of older consoles and small LCDs with RGB connections: http://benheck.com/forums/viewtopic.php ... 48d20ecd8c

I am just not sure about the sync, I think consoles sync off of the green line (unless it is possible that the Composite input will double as sync?). If I get $20 I can buy all the parts but the RGB->NTSC from Mouser or Digikey and try it, that is a pretty low cost of entry in my opinion, Thanks Uze .

I don't know that one off the top of my head... The problem with some of those older parts is that they can require a small army of weird caps and inductors to function.

Yes, that was a concern I had.

One other option-- locate an old Playstation 1 or Sega Genesis at goodwill/fleabay/etc. They'll have an RGB->NTSC converter in them. If you buy an otherwise dead system they can be pretty cheap. The PS1's used the Sony CXA2075 which is really nice. (great picture quality) Unfortunately that picture quality came at a price-- namely about 3/4W power consumption!

Yep, just as I woke up today I remembered my pile of Playstations that I rescued from second hand stores and wondered if they contained an RGB->NTSC chip, thanks for the confirmation .

Yep, that just cuts the parts count down and allows for balanced color (leave the LSB of red and green 'off' and the MSB's of RGB then track 1:1) and you should get good grays free of tint.

That is OK, I am more concerned about less complexity and total cost, but the accurate grayscale is a bonus.

Edit: wrong link, fixed.

[nubie]

Well, I found an SCPH 1001 and a 9001, no sign of my other console (I am not sure whether it is the 3 5 or 7 series).

The 9001 is so dense I bet the RGB converter has been absorbed into a multipurpose chip. The 1001 contains a CXA1645M chip, but it looks like the circuit contains quite a few caps and an SMD inductor! Sony state of the art

If your Stamp could come in under or around $30 I might as well just wait for it and save myself the headache . Any word on possible cost?

I imagine an UzeMicro system made out of an NES controller with a 2.6" LCD* embedded (would have to move the start/select likely), probably just the influence of the crazy people at Benheck forums (who am I kidding, I was crazy before I found that place )

* http://cgi.ebay.com/Hip-Gear-XBOX-Contr ... dZViewItem

[havok1919]

The 9001 is so dense I bet the RGB converter has been absorbed into a multipurpose chip. The 1001 contains a CXA1645M chip, but it looks like the circuit contains quite a few caps and an SMD inductor! Sony state of the art

The '1645 is a good chip too. I think some models of the Genesis used that as well. The inductor is probably part of the trap circuit and could likely be left out and still work.

If your Stamp could come in under or around $30 I might as well just wait for it and save myself the headache . Any word on possible cost?

My mental target was $29, but looking at the COGS and not knowing assembly yet I have a sneaking suspicion it'll probably need to be more. My plan at the moment is to build up enough to 'seed' the market (say at that $30 price-- there's only ~50ish people on this board at the moment and my prototype run will yield like ~80 boards, assuming they work!). Then once we get some momentum going on development I'll probably price at the $35-39 point. (A BASIC Stamp 2 is ~$39 in 100's and doesn't have the video encoder or SD card socket adding to the costs!)

Then I'll have a few 'baseboards' in the $20-50 range depending on features. ($20 is just a basic 'gaming' SKU; joystick port, A/V, power input, etc. $50 is more 'everything'; USB->RS232, MIDI, A/V, Ethernet, joysticks, power supply and joypad included, etc.)

For people that can't/don't want to build their own, a total system for $59 in qty 1 seems pretty reasonable to me. Some people will just prefer to make their own and save some bucks-- I don't want to go so low in price that I can't ever recover my time/development costs.

I imagine an UzeMicro system made out of an NES controller with a 2.6" LCD* embedded (would have to move the start/select likely), probably just the influence of the crazy people at Benheck forums (who am I kidding, I was crazy before I found that place )

Exactly. I'm thinking of making some available without the pin populated so they'll have less height. Good for stashing inside a controller. I bought some LiPoly batteries as well. Going to go portable, might as well run for a while.

Parallax actually has a video display that looks pretty hackable for that purpose-- not cheap, but still: http://tinyurl.com/6kegbr

-Clay

[nubie]

The '1645 is a good chip too. I think some models of the Genesis used that as well. The inductor is probably part of the trap circuit and could likely be left out and still work.

If your Stamp could come in under or around $30 I might as well just wait for it and save myself the headache . Any word on possible cost?

My mental target was $29, but looking at the COGS and not knowing assembly yet I have a sneaking suspicion it'll probably need to be more. My plan at the moment is to build up enough to 'seed' the market (say at that $30 price-- there's only ~50ish people on this board at the moment and my prototype run will yield like ~80 boards, assuming they work!). Then once we get some momentum going on development I'll probably price at the $35-39 point. (A BASIC Stamp 2 is ~$39 in 100's and doesn't have the video encoder or SD card socket adding to the costs!)

Then I'll have a few 'baseboards' in the $20-50 range depending on features. ($20 is just a basic 'gaming' SKU; joystick port, A/V, power input, etc. $50 is more 'everything'; USB->RS232, MIDI, A/V, Ethernet, joysticks, power supply and joypad included, etc.)

For people that can't/don't want to build their own, a total system for $59 in qty 1 seems pretty reasonable to me. Some people will just prefer to make their own and save some bucks-- I don't want to go so low in price that I can't ever recover my time/development costs.

Thanks, I might as well wait for that, I know you need to make it worth your time, and your final price is very reasonable too (of course for under $20 I don't know if I will be able to hold off )

I imagine an UzeMicro system made out of an NES controller with a 2.6" LCD* embedded (would have to move the start/select likely), probably just the influence of the crazy people at Benheck forums (who am I kidding, I was crazy before I found that place )

Exactly. I'm thinking of making some available without the pin populated so they'll have less height. Good for stashing inside a controller. I bought some LiPoly batteries as well. Going to go portable, might as well run for a while.

Parallax actually has a video display that looks pretty hackable for that purpose-- not cheap, but still: http://tinyurl.com/6kegbr

-Clay

Cool on the li-ion, I am eying my pair of Walmart $12 cellphones as battery/charger parts

Those screens look to be high quality, but the price is a lot. (I think there are some "controls, battery and screen" portables from China that cost around $30, if the cartridges contain the system we could put the Uze inside the cartridge and have a large base of portable Uzeboxes http://www.dealextreme.com/products.dx/category.606 ) I am not 100% sure if that is how the onestation works, but if it is then it might not be a bad idea.

Edit, it appears the OneStation may need an LCD controller. Ugh.

http://img354.imageshack.us/my.php?image=mbbackem4.jpg
http://img213.imageshack.us/my.php?imag ... iewdg2.jpg
http://img184.imageshack.us/my.php?imag ... ackuj5.jpg
http://img339.imageshack.us/my.php?imag ... ontnm5.jpg

[havok1919]

Cool on the li-ion, I am eying my pair of Walmart $12 cellphones as battery/charger parts

Check out the LiPoly pack/charger that DealExtreme has for those RC helicopters... lot of juice in those!

I am not 100% sure if that is how the onestation works, but if it is then it might not be a bad idea.

Ahhh, the Onestation. I've torn one of those and another similarly price unit from BestBuy apart. The BestBuy one was running some sort of YUV output direct to the panel, but I *think* the OneStation screen (at the time anyway) was RGB. The only problem with the RGB (digital) LCD's is that you need to supply pixel clock synchronously with the pixel data (and occasionally a "data enable" and other signals) to show when the data's valid.

I was thinking about that a bit and it might be possible to build a little external clock divider setup... Knock down the 4FSC clock and strip out the HSYNC pulses and use the complement of those for a data enable. I didn't spend much more time thinking on that though since the somewhat ugly issue of pixel counts is harder to get around. (ie, you have to shift in a whole LCD scanline of pixels based on the LCD's resolution-- and it *won't* be 1:1 UZEBOX video resolution, so you need a way to black bar the edges... Getting complicated... Not impossible, but pretty tricky in realtime without building a scanrate convertor almost.)

-Clay