Another failed ST -> vga experiment for me :)

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TheNameOfTheGame
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Re: Another failed ST -> vga experiment for me :)

Postby TheNameOfTheGame » Wed Jan 23, 2013 5:51 pm

Oh cool, yea I would like to give this another shot with the RGB buffer. Would a 4050 type buffer be ok here?

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Re: Another failed ST -> vga experiment for me :)

Postby soviet9922 » Wed Feb 03, 2016 12:41 am

Build your shematic and what can i say works great ! hurra hurray for you sir !

Image

Image

Image

1024MAK wrote:Here is the schematic for the simplified version of the circuit that I use with the GBS-8200 V4.0 board.

74LS86 sync circuit V0,6.gif


It has been tested with an Atari STFM.
The chip (IC1) is a 74LS86.
All resistors are 250mW 5%. C1 is a 100nF capacitor, the type and voltage rating are not critical, but I suggest a ceramic type.

I used the P9 power connector on the GBS-8200 V4.0 board to "steal" a +5V supply for this circuit. Red is +5V, black is 0V/GND.
Connect the Atari STF(M)/STE up as per the table below.
On the schematic diagram, the output is called "Comp Sync out" but in the table I refer to the same signal as CSync.

Code: Select all

   Atari      signal      wire colour   GBS-8200 V4.0 board
13 pin DIN                                 P11 connector
    6 ------green video---green wire------------"G"
    7 ------red video-----red wire--------------"R"
    9 ------HSync---------to 78LS86 circuit
   10 ------blue video----blue wire-------------"B"
   12 ------VSync---------to 78LS86 circuit
   13 ------Ground--------black wire------------"GND"
            CSync from----grey wire-------------"S"
            78LS86 circuit
            No connection-yellow wire-----------"VS"


Mark

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Re: Another failed ST -> vga experiment for me :)

Postby soviet9922 » Mon Feb 08, 2016 5:55 pm

This is very intersting, http://www.ebay.com/itm/401052782833?_t ... 833.N36.S1
Only use 3 ICs and a capacitor and resistors what kind of ics use ?.

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Re: Another failed ST -> vga experiment for me :)

Postby galax » Mon Feb 08, 2016 8:26 pm

soviet9922 wrote:This is very intersting, http://www.ebay.com/itm/401052782833?_t ... 833.N36.S1
Only use 3 ICs and a capacitor and resistors what kind of ics use ?.

RGB -> YCbCr is a simple transformation; each of Y, Cb, and Cr is a linear function of R, G, and B. The main part of the circuit will be resistors that correspond to the coefficients on R, G, and B and some op-amps to help combine the signals together. There are probably 2 op-amps on each of those ICs, so 6 total.

This device would be useful if your TV can display a 15kHz horizontal video signal and has a YCbCr input but no RGB input, it doesn't do any scan conversion to help with TVs that can't display 15kHz.

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Re: Another failed ST -> vga experiment for me :)

Postby soviet9922 » Mon Feb 08, 2016 8:34 pm

galax wrote:
soviet9922 wrote:This is very intersting, http://www.ebay.com/itm/401052782833?_t ... 833.N36.S1
Only use 3 ICs and a capacitor and resistors what kind of ics use ?.

RGB -> YCbCr is a simple transformation; each of Y, Cb, and Cr is a linear function of R, G, and B. The main part of the circuit will be resistors that correspond to the coefficients on R, G, and B and some op-amps to help combine the signals together. There are probably 2 op-amps on each of those ICs, so 6 total.

This device would be useful if your TV can display a 15kHz horizontal video signal and has a YCbCr input but no RGB input, it doesn't do any scan conversion to help with TVs that can't display 15kHz.


Yes but most new flat tvs have ycbcr and also most new crt tvs, do you new any shematic to build such converter ?.

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Re: Another failed ST -> vga experiment for me :)

Postby wietze » Tue Feb 09, 2016 10:24 am

soviet9922 wrote:Build your shematic and what can i say works great ! hurra hurray for you sir !

Image

Image

Image

1024MAK wrote:Here is the schematic for the simplified version of the circuit that I use with the GBS-8200 V4.0 board.

74LS86 sync circuit V0,6.gif


It has been tested with an Atari STFM.
The chip (IC1) is a 74LS86.
All resistors are 250mW 5%. C1 is a 100nF capacitor, the type and voltage rating are not critical, but I suggest a ceramic type.

I used the P9 power connector on the GBS-8200 V4.0 board to "steal" a +5V supply for this circuit. Red is +5V, black is 0V/GND.
Connect the Atari STF(M)/STE up as per the table below.
On the schematic diagram, the output is called "Comp Sync out" but in the table I refer to the same signal as CSync.

Code: Select all

   Atari      signal      wire colour   GBS-8200 V4.0 board
13 pin DIN                                 P11 connector
    6 ------green video---green wire------------"G"
    7 ------red video-----red wire--------------"R"
    9 ------HSync---------to 78LS86 circuit
   10 ------blue video----blue wire-------------"B"
   12 ------VSync---------to 78LS86 circuit
   13 ------Ground--------black wire------------"GND"
            CSync from----grey wire-------------"S"
            78LS86 circuit
            No connection-yellow wire-----------"VS"


Mark


I used to use a GBS 8200 board myself, until I noticed something; the board does not display different colors on screen for colour values that are close to each other:
for example $776 and $777 both show as white. I asked Gizo of DHS (who used a 8200 converter too) to reproduce this case; and he found the same results.

Would you be willing to fire up neochrome or any other paint program, and draw some different colors that are near each other (but essentially different) and either validate or invalidate my claim that the GBS is not able to display all the colors used by the Atari?

I'd love to know.

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Re: Another failed ST -> vga experiment for me :)

Postby soviet9922 » Tue Feb 09, 2016 2:39 pm

I noticed that the image compared to rgb monitor look like sh*t when i get home i will fire it up and take pictures, i think you are right o that.

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Re: Another failed ST -> vga experiment for me :)

Postby galax » Tue Feb 09, 2016 2:58 pm

wietze wrote:I used to use a GBS 8200 board myself, until I noticed something; the board does not display different colors on screen for colour values that are close to each other: for example $776 and $777 both show as white.


If this is only happening with the brightest colours, it's possible that you need slightly higher valued resisters on the R, G, and B signals coming out of your ST. This can happen with VGA monitors too, which expect 0.7v to mean 'maximum', whereas the ST are 1v, so the brightest values get truncated.

Of course your explanation could be right too- I'll try it next time I have my GBS handy and see if it happens with mine. I did spend a while finding the optimal resistor value though so it's likely that I would have tested for this.

soviet9922 wrote:I noticed that the image compared to rgb monitor look like sh*t

Yes that's the reason that mine only gets used in emergencies.

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Re: Another failed ST -> vga experiment for me :)

Postby galax » Tue Feb 09, 2016 3:52 pm

soviet9922 wrote:Yes but most new flat tvs have ycbcr and also most new crt tvs, do you new any shematic to build such converter ?.

This page has some circuit diagrams at the bottom that look about right to me: http://elm-chan.org/works/yuv2rgb/report.html

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Re: Another failed ST -> vga experiment for me :)

Postby wietze » Wed Feb 10, 2016 7:52 am

galax wrote:
wietze wrote:I used to use a GBS 8200 board myself, until I noticed something; the board does not display different colors on screen for colour values that are close to each other: for example $776 and $777 both show as white.


If this is only happening with the brightest colours, it's possible that you need slightly higher valued resisters on the R, G, and B signals coming out of your ST. This can happen with VGA monitors too, which expect 0.7v to mean 'maximum', whereas the ST are 1v, so the brightest values get truncated.

Of course your explanation could be right too- I'll try it next time I have my GBS handy and see if it happens with mine. I did spend a while finding the optimal resistor value though so it's likely that I would have tested for this.

soviet9922 wrote:I noticed that the image compared to rgb monitor look like sh*t

Yes that's the reason that mine only gets used in emergencies.


Correct. Currently I use no resistors at all; which may cause it. So I would wonder what the results are that people are getting that ARE using them :) Im interested to see your results.

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Re: Another failed ST -> vga experiment for me :)

Postby galax » Wed Feb 10, 2016 1:47 pm

The image is OK except for the lag and the artifacts discussed here when things move on screen: http://atariage.com/forums/topic/230827 ... -monitors/

Example video here, watch the distortion around the mosue pointer: http://youtu.be/uh6avr5w9uA

I haven't used my 8200 with the ST since I found an LCD monitor that can show all ST resolutions: http://atariage.com/forums/topic/230561 ... lcd-1970vx

I still used the 8200 with the ZX Spectrum and BBC Micro for a while but stopped when I got a cheap used Extron scan converter that does a much better job. I still have it for emergencies though, as it's a lot better than nothing.

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Re: Another failed ST -> vga experiment for me :)

Postby soviet9922 » Tue Feb 16, 2016 7:58 pm

I have a question the composite output in this circuit could by negative or positive ?.



1024MAK wrote:Here is the schematic for the simplified version of the circuit that I use with the GBS-8200 V4.0 board.

74LS86 sync circuit V0,6.gif


It has been tested with an Atari STFM.
The chip (IC1) is a 74LS86.
All resistors are 250mW 5%. C1 is a 100nF capacitor, the type and voltage rating are not critical, but I suggest a ceramic type.

I used the P9 power connector on the GBS-8200 V4.0 board to "steal" a +5V supply for this circuit. Red is +5V, black is 0V/GND.
Connect the Atari STF(M)/STE up as per the table below.
On the schematic diagram, the output is called "Comp Sync out" but in the table I refer to the same signal as CSync.

Code: Select all

   Atari      signal      wire colour   GBS-8200 V4.0 board
13 pin DIN                                 P11 connector
    6 ------green video---green wire------------"G"
    7 ------red video-----red wire--------------"R"
    9 ------HSync---------to 78LS86 circuit
   10 ------blue video----blue wire-------------"B"
   12 ------VSync---------to 78LS86 circuit
   13 ------Ground--------black wire------------"GND"
            CSync from----grey wire-------------"S"
            78LS86 circuit
            No connection-yellow wire-----------"VS"


Mark

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Re: Another failed ST -> vga experiment for me :)

Postby jonathanm » Sat Sep 17, 2016 1:37 pm

Hi,

I built the simplified circuit using the 74HC86 IC, four resistors and a cap and it works well in 1024x786 with my STE, however I too have the distortion effect when moving the mouse cursor, so would like to give the 1881 circuit a go as well to fix it. Does anyone have a simple circuit diagram I could follow please? I'm afraid I'm not really electronic-savvy enough to follow the instructions below as they are. I would only want to use this with the Atari STE (for the moment, never know what the future holds!) and an LCD monitor. I have a 4:3 Sony LCD that appears to be working well with the 74HC86 circuit.


Guest wrote:ok i am in a good mood so i will tell you how to fix it :coffe:

what you use is a hex buffer ic {not an inverter}

double duffer each colour using a cmos ic..

RED OUT -|>-|>--RED IN to card
BLUE OUT -|>-|>--BLUE IN to card
GREEN OUT -|>-|>--GREEN IN to card
use an LM1881 ic to take apart the composite sync out {pin 2}
to vsync and hsync .. ODD setting on the 1881 made
use five 150R resistors
one on each RGB and the two syncs to ground at the board side ...
to form a load balanced input to each
i will draw the schematic if you need it
i just stick to a skybox dvd input works magic on an LCD TV
or you can use the dvd input on the tv for med and low and the rgb in for hires {nice pic!!!}
the reason for using the buffers to correct the added latency of the sync back to the rgb frame inputs
adding the buffers to RGB adds time that the 1881 steals .. from the frame
this way you wont get any blocks moving under the mouse
this is caused by the non interlacing problem ive seen the same issue with some capture cards on pc's
the mouse block using transitions to move it
the block get lighter between the two frames space when interlaced will pick this up as a moving block
ie the non interlaced framing is in the wrong time period .. of sync
if you use separate sync input the codec on the converter board keeps better timings

all ic's have latency
if your not using a lm1881 you should

as the sync outputs from the atari ST are inverted for NON TTL levels you need atleast to invert them
but adding buffers is better... by far

cmos buffers @12vsupply latency is around 150ns or so
the lm1881 has a processing latency of about 300ns
so double buffer the RGB also... :contract:

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Re: Another failed ST -> vga experiement for me :)

Postby TeX38 » Tue May 30, 2017 8:11 am

Scarlettkitten wrote:It's simply

Atari..................Converter

R-------------------------R
G-------------------------G
B--------------------------B

H
Combined >--------------S
V


The RGB converter is an GBS 8200 V4



Hmm...I have the same board and so far I have been unable to get it to work with my STF.
Mine is made in 2015 so very recent.

How did you combine the V and H sync lines?

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Re: Another failed ST -> vga experiement for me :)

Postby TeX38 » Thu Jun 01, 2017 5:27 am

Scarlettkitten wrote:I recently bought one of those RGB to VGA devices & have produced a pretty good picture by combining H&V sync.

ImageImageImageImage
Image



hi skarletkitten,
All of the pictures from this post are missing, could you re post them if available please?

I am trying to get my converter working with my Atari ST, so far without luck.

Mine is the V4 8200 year 2015 model.

Are th Vsync and Hsync combined directly without any resistors?
if so, is this safe?

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Re: Another failed ST -> vga experiment for me :)

Postby TeX38 » Sun Jun 11, 2017 9:12 am

Silly_Pony wrote:I threw that circuit together last week, it does a great job keeping the image stable.

For switching to mono mode I use a vga switcher, and a dpdt switch that either provides 5V for the sync mixer and GBS board, or connects MONO DETECT to ground. It's all mounted in my homemade ST case with a separate keyboard.



Hi Silly_Pony
Your homemade case sounds like FUN, do you have pictures please, would love to do this myself.

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Re: Another failed ST -> vga experiment for me :)

Postby Sincity » Mon Aug 07, 2017 2:37 am

To combine or not to combine H&V sync? I've been reading different things.

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Re: Another failed ST -> vga experiment for me :)

Postby jonathanm » Thu Jan 18, 2018 10:15 am

Has anyone managed to get a faultless video output to a modern LCD / LED monitor? Still would really like to get this sorted as my old Atari CRT's days are undoubtedly numbered.

Double buffering using the lm1881 sounds like it is the way to go but I don't have a circuit diagram for that, is there anyone here with electronics know-how able to help please?

Also, has anyone come across a good way to connect wires to the DIN plug for the Atari STE monitor port? It's hellishly tight and therefore difficult to do with a soldering iron!

Really hoping we can get some sort of finished video converter box project completed for this.


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