The Newbrain Forum

Hi Michael,

That is +1 for you i ll check it out when time comes for the VGA module but is certainly an easy to use controller.it has more features that i want but it will as long as i can transfer the video screen from Ram to the Vram in the controller fast  enough.

Many thanks ,

Chris

Yes, the Spartan clearly has the advantage of parallel interface. (It's the BartStation you think of, right?)

I think the uVGA is only intended to be used to manipulate it's one videoRAM. Not transferring a hole VideoRAM to it.

To move a 640x256 VideoRAM serial with 4MHz will take roughly 1/4 second not counting overhead in the uVGA.... naa ain't going to work. Maybe if it's a 8bit bus. (~3.5mS)
I guess 15 instructions at an average of 3cycles and ...what 20k of videoRAM. I'm not up to speed on how it's stored in the NB.

One way or the other, the VideoRAM has to be moved to an advanced VGA-controller.
It is going to take cpu-time.

How about a second Z80, doing only that task?.... Just a idea...

bg
Michael

Most suitable so far is this project using a XC95108(PLCC) from xilinx (100 pins) that can deliver 640x480 monochrome vga signal which is more than enough for the newbrain.

Project page : http://elm-chan.org/works/crtc/report.html

Circuit Diagram : http://elm-chan.org/works/crtc/circuit_diagram.png
and modifications needed for vga monochrome : http://elm-chan.org/works/crtc/vga.png

Schematics to build a parallel download cable needed to programm the chip (Softeare is available for free at xilinx site. (they sell this for $125, $225 for the usb version).
http://www.xilinx.com/itp/xilinx4/data/ … ndixb.html

Last edited by cdesp (31-03-2010 16:09:32)

No I haven't but according to them it should be ok with RAM CHIPs up to 150ns.

The reading of course will be done by the xilinx putting the z80 on hold and taking control of the busses to refresh the screen.

So i think it would be faster than the real newbrain but that remains to be seen.

Anyway it is not the time to get into this i now have to make two pcbs one for the LCD 2x16 and one for the clock circuit (this gives all clocks from 4MHZ down to 1HZ by dividing by 2) to make room at my rasters for the rs232 interface that would make easier for me to change the EEPROM Contents by transfering data through the z80 directly to eeprom.

If someone has a better solution for the TFT/LCD Interface please let me know.

I found a new chip from epson which fits the project very well with less pins than the previous one 64 now from 144.

http://vdc.epson.com/index.php?option=c … mp;gid=210

Yes it seems a good choice and a cheap one according to your research.
As for the panel its too early to start looking for one since i am busy finalizing the PS/2 Keyboard Interface.
But as you said it would be quite expensive hope for a price less than 100 Euros.
It should be capable of 640x480 at least but i think i will not find anything less than 800x600.

Screen will be the most difficult and complicated part of the project.

Hi Chris...

Now you found the Epson chip.. ok, but take a look at this display manufacturer.

http://www.display-elektronik.de/lcd-gr … -table.htm

This interfaces directly with a 8bit databus.
To complicated to use..?

This Swedish electronic-supplier sell it to around 120€
https://www.elfa.se/elfa3~eu_en/elfa/in … ;toc=20375

I have a hard time to find 640x256 display, but this Panasonic keeps popping up.
http://www.aliexpress.com/product-fm/44 … alers.html

br
Michael

Another sollution http://www.mitsutech.com/RA8835.html it's an older epson compatible chip.
this chip supports 640x256 mono which is the max resolution for NB.
But the problem with lcd is that the screen ratio is not 4:3 in that resolution so it should be like a widescreen .

One solution would be if we can double the vertical resolution so the res would become a  pseudo 640*512 but i doubt if we could find a chip to support this.

I did some searching for an lcd panel that has the 640x256 resolution and nothing came up at a resonable price.
So since that resolution is made for pal systems i think the system should work with PAL output at 640x256 and use a PAL lcd screen which come at a very resonable price and several sizes.

some examples:

http://www.ebay.co.uk/itm/7-TFT-LCD-Rea … 289wt_1139

http://www.ebay.co.uk/itm/7-TFT-LCD-Rea … 27c683af75

I manage to get a monochrome signal using the xilinx 9572 CPLD. I am using the 16Mhz crystal so ia can put 1024 pixels on screen and 305 lines but i reduce this to 640x256 to be compatible. I ll order a 13,5 Mhz crystal as this is better for PAL signals. The D/A converter i am using is as simple as it gets several resistors forming a R/2R ladder for 3 bits of information data, hsync and vsync. I have to make something better to stabilize the signal but for now it is good.
I ll try to Interface this with the cpu and see what will happen.

Pictures at the gallery.

The laptop screen will be, as the original, a monochrome composite signal and you can connect any compatible tv screen lcd or crt.

I am using two CPLD chips from XILINX one XC9572 for generating synchronisation signals (VSync and HSync) and the other is the XC95108 that has all the logic to read data from the RAM chip, put the cpu on hold (BUSREQ) and of course displaying either text (80/40 chars) or graphics.

I manage to do that but the signal is not as stable as i would like, and i have some problems to solve until i can say it is ok.

Check the videos to see

40 chars
http://youtu.be/-wjAxnkiWLo

80 chars
http://youtu.be/nUy2k_mx3Qo

Graphics
http://youtu.be/_NGrQRU40HM