Another failed ST -> vga experiment for me :)

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

Postby 1024MAK » Thu May 03, 2012 11:18 pm

Shredder11 wrote:Mark, have you done any more tweaks or revisions to your circuit since v0.6? :coffe:

On the Atari ST - nope.
Connecting to Acorn Electron, BBC B and Master 128 - yes :D
See here http://stardot.org.uk/forums/viewtopic. ... =60#p46488

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

Postby 1024MAK » Thu May 03, 2012 11:27 pm

thgill wrote:However, I guess I don't understand why you guys are needing to use such a complicated circuit.
Can't you just use Pin 2 from the ST monitor socket and feed that composite video/composite sync into a LM1881 circuit (to clean up the signal) and use the composite sync outputted (ignoring the other outputs) from it into the composite sync input on the GBS? I guess I don't understand the need to feed it Horizontal and Vertical sync.

:arrow: Alas, the GBS-8200 V4.0 board does not like the composite video signal from pin 2 on Atari STs that have an internal TV modulator (may be okay with Atari STs that don't have an internal TV modulator). It is also not happy with separate Horizontal and Vertical sync. signals :( .
This circuit is not very complicated (viewtopic.php?f=15&t=17153&start=100#p203262).
You could use a LM1881 circuit, but why when you have access to the Horizontal and Vertical sync. signals from the Atari ST? :?:

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

Postby Silly_Pony » Fri May 04, 2012 12:27 am

thgill wrote:I used one of these briefly last year on an Amiga 1200 and was never satisfied with the results. And that was even feeding its VGA output into a CRT monitor.

Odd shifting pixels (like it was trying to auto correct itself, especially on the mouse cursor) and frame rate conversion converts all PAL 50Hz stuff to 60Hz so you get jerky scrolling in games and demo's.


Honestly they're crap boards. I only use mine for games, since those run in ST LOW.

For gaming on the same monitor you run ST HIGH on they're great. The crappy scaling looks like composite but at twenty quid a pop you can't moan.
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Re: Another failed ST -> vga experiment for me :)

Postby thgill » Fri May 04, 2012 2:02 am

1024MAK wrote: :arrow: Alas, the GBS-8200 V4.0 board does not like the composite video signal from pin 2 on Atari STs that have an internal TV modulator (may be okay with Atari STs that don't have an internal TV modulator). It is also not happy with separate Horizontal and Vertical sync. signals :( .
This circuit is not very complicated (viewtopic.php?f=15&t=17153&start=100#p203262).
You could use a LM1881 circuit, but why when you have access to the Horizontal and Vertical sync. signals from the Atari ST? :?:

Mark



Because a LM1881 circuit is mega simple (1 chip, 1 resistor and 2 small caps) in comparison to that circuit you posted up needing both H and V sync.

I am kinda surprised that a LM1881 wouldn't strip/clean up the composite video and provide a composite sync good enough for the GBS to work with it. Its known for being very good at that.

I might have to pick up another GBS board sometime for experimenting. You can pretty easily integrate a LM1881 circuit onto the GBS board. And with a little bit of work

you could even mount a Scart socket on it making it mucho easy for plugging in standard scart cables to use with it. I would probably remove the front mounted VGA and component inputs connectors to make room for a female scart socket.
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Re: Another failed ST -> vga experiment for me :)

Postby 1024MAK » Fri May 04, 2012 8:47 am

thgill wrote:Because a LM1881 circuit is mega simple (1 chip, 1 resistor and 2 small caps) in comparison to that circuit you posted up needing both H and V sync.
All required signals are available on the same 13 way connector and on all versions of the Atari ST.
thgill wrote:I am kinda surprised that a LM1881 wouldn't strip/clean up the composite video and provide a composite sync good enough for the GBS to work with it. Its known for being very good at that.
Confused :? I do have some LM1881 ICs but have not tested your suggestion, nor have I said that this would not work.

With my circuit (viewtopic.php?f=15&t=17153&start=100#p203262), if you want to construct a minimalist circuit, delete resistors R4, R5 and R6. If you are using a well decoupled 5V supply, delete capacitor C1.
That then leaves just IC1 and R3. So now only two components.
I included input and output resistors to provide some basic protection for the LS logic chip.

The GBS-8200 V4.0 board that I bought was supplied without a case. For a simple neat set-up, all that is needed is a suitable plastic case then all the electronics can all be included inside. You have a choice of three connectors to connect the input signals to (electrically all the connectors are linked).

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

Postby Shredder11 » Fri May 04, 2012 10:20 am

1024MAK wrote:
Shredder11 wrote:Mark, have you done any more tweaks or revisions to your circuit since v0.6? :coffe:

On the Atari ST - nope.
Connecting to Acorn Electron, BBC B and Master 128 - yes :D
See here http://stardot.org.uk/forums/viewtopic. ... =60#p46488

Mark



Hey that is good to hear about the Beeb (still nowhere near to getting one yet). The other day I spent a couple of hours soldering and repairing my sister's Mitac Mio 168 Pocket PC, and when finished I decided to look up those parts for the 8200 v4 board here from that Ebay seller you mentioned. I just need a suitable case and PCB and then I can start testing with the STE.

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

Postby thgill » Fri May 04, 2012 12:13 pm

1024MAK wrote:Confused :? I do have some LM1881 ICs but have not tested your suggestion, nor have I said that this would not work.

With my circuit (viewtopic.php?f=15&t=17153&start=100#p203262), if you want to construct a minimalist circuit, delete resistors R4, R5 and R6. If you are using a well decoupled 5V supply, delete capacitor C1.
That then leaves just IC1 and R3. So now only two components.
I included input and output resistors to provide some basic protection for the LS logic chip.


My mistake, I was thinking you indicated the LM1881 wouldn't work.

:oops:

Its good to know, though, that your circuit does work to combine H + V into a usable composite sync for the GBS board.


I have both a regular 520ST and a 520STe, so I should pick up another GBS board and see what kinda results I get with them.
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Re: Another failed ST -> vga experiment for me :)

Postby TheNameOfTheGame » Sat Oct 13, 2012 6:46 pm

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



Finally got around to prototyping this sync combiner circuit. It does work, I have a stable picture on my lcd monitor using an ste.

However, there are some weird scaling issues under and around the mouse. So that when the mouse is moved, a small part of the display picture around the mouse moves, sort of like a wave or ripple around the mouse pointer. More pronounced in medium res than low.

I have tried two lcd monitors and same results. Ran the circuit with an GBS-8220 v3 (with supposedly v4 firmware) and a HD 9800 v5. Both have the weird scaling issues. Neither of my monitors like the 640x480 mode from either board (the picture is stretched and off-center), but do best in 800x600. 1024x768 works too.

The 1360x768 output does work, but my monitors are 4:3 so it is a little odd looking, but the rippling around the mouse isn't as bad.

Anyone have any ideas to reduce the scaling/rippling effect from the mouse movements?

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

Postby Guest » Sun Oct 14, 2012 12:20 pm

ye you need to fine tune the boards menus for sync etc... then save it to the onboard rom

the best lcd i tried is a square type IBM it worked well in all modes the widescreen ones always have issues of sorts

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

Postby nativ » Sun Oct 14, 2012 4:53 pm

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

Postby Guest » Mon Oct 15, 2012 8:52 pm

nativ wrote:http://www.ebay.co.uk/itm/5-8G-8-CH-Wireless-FM-Audio-Video-Module-A-V-Receiver-for-VCD-DVD-DVB-PSP-to-TV-/230764762871?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item35baa6d6f7


can things like this be used?


cant see why it cant support RGB

dont see the use for it

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

Postby calimero » Wed Nov 28, 2012 11:16 pm

TheNameOfTheGame wrote:However, there are some weird scaling issues under and around the mouse. So that when the mouse is moved, a small part of the display picture around the mouse moves, sort of like a wave or ripple around the mouse pointer. More pronounced in medium res than low.

same here :(

I made video with this "weird scaling issues under and around the mouse"

http://youtu.be/pKfnsqwW9WY

and I did not find way to eliminate it!
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Re: Another failed ST -> vga experiment for me :)

Postby Guest » Thu Nov 29, 2012 3:34 am

i made a video detailing exactly what too do http://youtu.be/8hgQA8eI6G8 :roll:

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

Postby calimero » Thu Nov 29, 2012 7:37 am

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

Postby wongck » Thu Nov 29, 2012 11:09 am

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

Postby DarkLord » Thu Nov 29, 2012 12:17 pm

Simbo, you're the man. :D
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Re: Another failed ST -> vga experiment for me :)

Postby TheNameOfTheGame » Thu Nov 29, 2012 5:10 pm

Funny! I was tempted to do this too haha, but decided to keep them around for who know what...

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

Postby Guest » Thu Nov 29, 2012 9:33 pm

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 experiment for me :)

Postby Guest » Thu Nov 29, 2012 9:55 pm

its worth pointing out that most people use the extrenal mixed sync output

and this goes through a TTL gate the separate sync doesn't so this introduces latency of sync to RGB frame number

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

Postby Shredder11 » Thu Nov 29, 2012 11:07 pm

Hey simbo, maybe upload a YouTube video of your Sky box thingy in action with your ST/E, so we can see how good it is. :cheers:

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

Postby Guest » Fri Nov 30, 2012 12:07 am

dont have an ste sold it to dal st works fine using it
would you like a photo of the st in med low on 22" hdmi??

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

Postby Shredder11 » Sat Dec 01, 2012 11:18 am

Yes that would be good to see as I plan on doing this, but probably on a 24", or whatever size will show a 4:3 ratio at the equivalent 17".

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

Postby Guest » Sun Dec 02, 2012 6:25 pm

Image

here is a monkey chart for the i/o
you can see the DVD input scart below the two standards on HDMI out

several other i/o are useful
they keep offering me a second Skybox free but i don't want it
perhaps if you phone them then you'll get a deal on a second box..... it is Christmas soon

before you say ooo its and output as per the detail in skys site
its bi-directional and acts as a scart 1 input or output depends what cable you use
and the signals set...

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

Postby Silly_Pony » Mon Dec 10, 2012 8:27 am

simbo2 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:


I'm bored enough to give this a go. I've got two of these GBS boards lying around, might as well get some use out of them
1040STe, 1040STf

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

Postby Silly_Pony » Tue Jan 22, 2013 9:42 pm

Simbo could you draw that schematic? I've got some spare time over the next week or so. Want to see how much of a difference it makes.

Cheers
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