Another failed ST -> vga experiment for me :)

[1024MAK]

I know most people love pictures, so here are some more....
First, another STE picture...

STE - Xenon 1.jpg

All the rest are from a STFM...

STFM Low Res.jpg

STFM Med Res.jpg

STFM - Xenon 1.jpg

STFM - Xenon 2.jpg

[spiny]

just ordered the bits to make the little sync combiner board

expect some foolish questions when I mis read the schematic

[1024MAK]

I had hoped to do some more work on this subject, as in try the 74HC86 chip and try to simplify the circuit.
But real life reduced my free time so I did not have time Sorry if anyone is waiting.

I get a day off work on Friday, so hopefully may make some progress then.
Meanwhile if you do want to have a go at the circuit I posted, note that it can easily be built on strip-board. Also some of the input pins line up with output pins on the other side of the chip. This means that at least two tracks under the chip do not need cutting. The rest do need cutting with a drill bit (or Veroboard / strip-board cutter).

Again, hopefully on Friday I can draw a strip-board layout.
Note that on the schematic that I posted, many lines cross with no connection. Where there is a connection, one line meets a straight line and at the junction there is a very small filled in circle, but I must admit that I made the circles a bit too small, so they are hard to see

Mark

[jokker]

Awesome work 1024MAK! Thanks for the creating that circuit...

Just ordered myself the IC's to build it myself.

[ralcool]

Might be a silly question

What happens if you're put mono through the GBS-8200 video converter?... flick the mono switch if you have one...

ST

[spiny]

Might be a silly question

What happens if you're put mono through the GBS-8200 video converter?... flick the mono switch if you have one...

ST

i was thinking about that earlier, but i couldn't rememner what the 'mono detect' pin needs ? (grounding ? )

[DrCoolZic]

If you have an Atari STE and you are brave the composite sync obtained by using an xor as proposed by 1024mak is available internally. If you look at the schematic http://info-coach.fr/atari/hardware/video.php#schematic you will see that the composite signal is available on pin 3 of U209 and the complemented csync on pin 6 of U211 (upper right corener
of the schematic) ...

[spiny]

cool, all the components turned up today, so i've been working out the best way to lay the board out

[ralcool]

Might be a silly question

What happens if you're put mono through the GBS-8200 video converter?... flick the mono switch if you have one...

ST

i was thinking about that earlier, but i couldn't remember what the 'mono detect' pin needs ? (grounding ? )

As I remember, we ground the mono detect pin, then link the Mono video output line to all the RBG inputs of usually VGA.

So if the job of the GBS-8200 video converter is to double the colour hsync to vga levels, what happens if we feed it 'mono' mode.

My switch box I built, was designed to suit a NEC multisync 3d, These days it operates a normal 19" lcd/vga screen in mono mode. I have a TV to one side now for colour operation.
The old SC1224 is dead. I feel my ST's modulator is dying too. No lcds I own can handle ST Low/Medium freqencies.

Another day .....

ST

[spiny]

ok, some patient soldering has resulted in this:






so, stupid question time:

do i need the jumpers fitted ?

I can follow the diagram (I think ...) but the actual purpose of the circuit is beyond me at the moment

[nativ]

If it's cold Jumpers and hats are recommended!

[Shredder11]

...and a SCARF cable

[1024MAK]

Way-hay
You had me going for a minute there Mr spiny
Slipping the 16 pin chip in a 18 pin socket...

To your question, yes JP1 and JP2 need jumpers fitted.
That's the ones connected to pins 1 and 9 of the chip.
I'm just having a look at your handiwork, back soon...

Mark

[spiny]

yeah, couldn't find the right size holder in my box of bits, obviously i need to buy more stock from ebay

i'm about 200 miles away from my house today, so it'll be tomorrow before fir the jumpers and fire it up and see what happens

[ralcool]

Something worth trying- some demos containing border removal tricks.

Maybe Level16 full screen from the Union... and many others.

Just to see if it trips up the scan converter.

ST

[1024MAK]

I'm just having a look at your handiwork, back soon...

It's all looking good Mr spiny
Everything looks like it is connected as per me schematic, well done that man

Unless you to want to experiment with other set-ups / configurations and or use it with other computers (maybe), leave the "HS out" (from IC pin 8 via R8) and the "VS out" (from IC pin 3 via R7) wires unconnected.

The jumper on JP1 selects whether the signal on IC pin 3 is a copy or an inverted copy of the input on pin 2, which is the Vertical Sync pulses from the Atari.
The jumper on JP2 does the same thing for the Horizontal Sync (output from pin 8 is a copy or an inverted copy of the input on pin 10).
The Vertical Sync and Horizontal Sync pulses are then mixed (added) by the next logic gate. Finally the now mixed (or composite) sync is fed to the last gate (pin 4). The jumper on JP3 selects whether the mixed (or composite) output signal on IC pin 6 is a copy or an inverted copy of the input on pin 4.

Why all the possible inverting you ask?

Well back in the simple days of monitors that were only designed to display a TV standard signal, there was none of this messing about. But then various companies started making computer video cards and monitors, some of which used different polarity sync signals... (search for CGA and EGA eg http://nemesis.lonestar.org/reference/video/cga.html)

Have fun...

Mark

[1024MAK]

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

[spiny]

success !

wired it up and its working a treat

thanks for taking the time to draw out the schematics and stuff

currently got the 'phalanx' demo on, border stuff seems fine so far, gonna dig out the union demo next

[nativ]

success !

wired it up and its working a treat

thanks for taking the time to draw out the schematics and stuff

currently got the 'phalanx' demo on, border stuff seems fine so far, gonna dig out the union demo next

Sounds like a good excuse for a demo session

[spiny]

couldn't find my copy of the union demo, so fired up one of our old screens instead:




only wierd thing is that the colours go a bit funny after a while, i see 'banding' which coincides with a raster that strobes one of the colours on screen. a bit strange, haven't seen this on other monitors or emulators. all the other demos i've thrown at it today have been fine though

[1024MAK]

@ Spiny - Glad you got it working

Just in case you were not aware - for normal (non-demo!) use, you can adjust the displayed screen size and position (both horizontally and vertical). So you can "remove" most of the border area

That fact that it works okay with most demo's means that it *should* work okay with an Atari fitted with Lascan. Got to go to work soon (I'm on nights this week) and the Atari that I have fitted with Lascan is in another part of the house. May have a play with this later in the week, or more likely next week.

Mark

[spiny]

success !

wired it up and its working a treat

thanks for taking the time to draw out the schematics and stuff

currently got the 'phalanx' demo on, border stuff seems fine so far, gonna dig out the union demo next

Sounds like a good excuse for a demo session

yes, i dug out the first ten or so demos that i have handy (the rest of my disks are in shoe boxes in the loft) and it was such fun I reckon i'm gonna spend this eveing revisiting the old classics I'm going to look up the 'cheat' for 'ooh crikey...' though, the navigation on the main screen is very frustrating

[Shredder11]

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

[Silly_Pony]

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.

[thgill]

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.


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.


I use a Sony PVM 20L2 broadcast monitor that takes care of all my RGB needs and I have built a ST RGB cable for it so I personally don't need one of these. Just curious why it appears to be so convoluted.