ST to VGA - Success :)

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Re: ST to VGA - Success :)

Postby Shredder11 » Sat Mar 13, 2010 5:55 pm

The more I read on here about the various STs out there, the more glad I am that I have STE machines! They seem much easier to upgrade and work with! 8)

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Re: ST to VGA - Success :)

Postby DrCoolZic » Sat Mar 13, 2010 6:03 pm

Shredder11 wrote:The more I read on here about the various STs out there, the more glad I am that I have STE machines! They seem much easier to upgrade and work with! 8)

Can you confirm your STE have an RF modulator. Thanks

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Re: ST to VGA - Success :)

Postby wongck » Sun Mar 14, 2010 1:44 am

Shredder11 wrote:The more I read on here about the various STs out there, the more glad I am that I have STE machines! They seem much easier to upgrade and work with! 8)


Well, they are newer afterall.
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Re: ST to VGA - Success :)

Postby Shredder11 » Sun Mar 14, 2010 11:32 am

DrCoolZic wrote:
Shredder11 wrote:The more I read on here about the various STs out there, the more glad I am that I have STE machines! They seem much easier to upgrade and work with! 8)

Can you confirm your STE have an RF modulator. Thanks


I've plugged them into various CRT TVs with an RF lead from the STE 'Television' ouput cinch on the back of the STE. So yes they do have an RF modulator I guess.

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Re: ST to VGA - Success :)

Postby spiny » Sun Mar 14, 2010 12:05 pm

all STe's have modulatars as far as I know.

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Re: ST to VGA - Success :)

Postby DrCoolZic » Sun Mar 14, 2010 6:58 pm

spiny wrote:all STe's have modulatars as far as I know.

The picture I posted shows that this is not the case :(

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Re: ST to VGA - Success :)

Postby Cyprian » Sun Mar 14, 2010 7:19 pm

DrCoolZic wrote:
spiny wrote:all STe's have modulatars as far as I know.

The picture I posted shows that this is not the case :(

I see two holes in your STE's case, it suggest that RF was removed by someone.
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Re: ST to VGA - Success :)

Postby DrCoolZic » Sun Mar 14, 2010 9:09 pm

Cyprian_K wrote:
DrCoolZic wrote:
spiny wrote:all STe's have modulatars as far as I know.

The picture I posted shows that this is not the case :(

I see two holes in your STE's case, it suggest that RF was removed by someone.

Actually this is not the case :) I do not know if you refer to the holes in the PCB or the holes in the chassis for the connector?
Anyway I just checked with 5 STE boards and they all have the same holes. The picture I have shown is from the latest batch of STE and it has a particularity compared to previous versions: The hole in the chassis for the output has a specially shaped piece of metal (sorry cant find the word in English) that is in contact with RF output (offer continuity between the chassis and the RF output). Other than that they are all the same.

Here is for example a picture of one of the first batch of STE (very very old one with a piggy back component and lot of floating wires)
video.jpg

As you can see this version has a plain hole for the RF output without the shielding piece.

What is important to note is the U403 and surrounding component not stuffed on the board. U403 is the place for the PAL/NTSC MC1377 encoder not present in version without RF modulator.
This is also clearly indicated on the schematic I have published earlier. Look in the right end corner of the schematic (sorry not easy to read) :(
To be more precise I have checked the different versions of the STEs (STE and MegaSTE) schematics. What happen is that for version with RF modulator you have the MC1337 and associated logic that drives the output pin 2 of the video connector. In version without the RF modulator this logic section is replaced by an analog amplifier (2N3904) that combine the H&V sync signal that drives the pin 2 of the video output connector. Of course in the two cases you have totally different type of signal. In the first case this is a composite PAL/NTSC signal (should be able to be used by a composite input of a TV set) and in the second case you have a composite sync signal.
Datasheet for the MC1377 PAL/NTSC encoder can be found at http://www.qsl.net/zl1wtt/pdf/MC1377.pdf
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Re: ST to VGA - Success :)

Postby DrCoolZic » Sun Mar 14, 2010 9:23 pm

To add a bit more on the subject:

I am considering to add the missing MC1377 and associated logic on an STE board to output s-video components. I did not considered it initially because it would be difficult to find the inductors (and may be the MC1377?). However in fact for this application the inductors are not needed as explained by ppera in http://ppera.07x.net/atari/stvid.php and the benefit in that case is that you can use the luma and chroma outputs directly from the chips and have a direct s-video output suppose to be better than a composite video :D
I first need to look carefully to the PCB to see if this is feasible.

PS: in the above link you have some nice pictures of boards with the video encoder logic for STE / Mega STE and STFM

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Re: ST to VGA - Success :)

Postby 1024MAK » Sun Mar 21, 2010 4:37 am

Here are some oscilloscope images showing the video outputs from an Atari STFM (with modulator). This is a UK model so operates to the PAL TV standard.
They show that the output on pin 2 of the Atari video connector is indeed composite video.
Also regarding the query about S-Video, well looking at these waveforms I don't think anyone is actually getting S-Video. What your equipment is probably doing is just using the information in the composite video feed (from pin 2) and ignoring the input from the "red / Chrominance" connection.
Why do I say this, well the waveforms for the red "RGB" video output from the Atari do not show the type of signal needed to correctly operate the circuitry for a chrominance input.

In all these images the blue trace is channel A of the oscilloscope which is connected to the Atari composite video (pin 2).
The red trace is channel B of the oscilloscope which is connected to the Atari red video output (pin 7).
For some of the traces I triggered the oscilloscope from the vertical sync output (pin 12).
Various images were used but I only provide those that show the important features most clearly. All were taken with the Atari set to low resolution video mode.

You can see that in this image there is not much of the red trace. This is the red video output from the Atari, but the picture the Atari is showing has no red in it, so therefore there is no "red" picture information transmitted by the red video signal. The composite (blue trace) carries lots of picture information.
A=comp, B=red with no red in the pic.png


You can see that there is a lot of picture information in both the blue and red traces. This is with a complex coloured picture being shown.
A=comp, B=red with some red in the pic.png


The red level (red trace) is fairly uniform for the middle section, but the composite (blue trace) varies much more as the different parts and colours of the image are displayed. You can clearly see the field sync pulses at the start of the trace.
A=comp, B=red low res desktop.png


This set of traces shows one and a bit "TV" lines, the bottom parts of the blue trace are the sync pulses, then the first "spiky" bit is the colour burst signal, then you get the picture information (with some gray bars). The level then drops down to "ground" (0V) and then there is another sync pulse for the next line.
test card #01.png


This is with the Atari displaying 6 vertical bars from white through various shades of gray to a very dark gray. The border is black. In this image (nearly one "TV" line) notice how similar the blue and red traces are. You can see a little bit of colour carrier information on the composite signal (blue trace) but not much as there is very little colour in the picture. Compare this to the image with six coloured vertical bars.
6 bars, white to dark gray.png


This image (nearly one "TV" line) clearly shows the type of signal you get for a composite colour signal (blue trace) when six coloured vertical bars are displayed. Note that above the ground (0V) level there are six steps corresponding to the six colours, each step is modulated with the colour carrier information. Compare this to the red video (red trace) which goes high only when there are red elements being displayed (for the yellow, magenta and red bars). Note that there is no modulated colour carrier information on this trace (but there is some noise and crosstalk from the composite colour signal).
6 colour bar picture.png


Atari Video Test Circuit.png
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Re: ST to VGA - Success :)

Postby spiny » Mon Mar 22, 2010 11:56 am

MAK:

so, can I take a lead from pin 2 and a GND and I have composite video ? or am I reading it wrong ?
My 'super video box' has composite input and would presumably be better quality than the RF I'm currently using :)

good work on the traces :)

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Re: ST to VGA - Success :)

Postby wongck » Mon Mar 22, 2010 12:00 pm

It is written in the pin out of the Atari ST monitor that pin 2 is the composite. :mrgreen:
http://pinouts.ru/Video/AtariStMonitor_pinout.shtml
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Re: ST to VGA - Success :)

Postby wongck » Mon Mar 22, 2010 12:05 pm

spiny wrote:so, can I take a lead from pin 2 and a GND and I have composite video ? or am I reading it wrong ?


I remember taking this signal from my 520STFM to a CCTV back in the early 90s. So it works. ;thumbs:
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Re: ST to VGA - Success :)

Postby DrCoolZic » Mon Mar 22, 2010 3:09 pm

1024MAK wrote:Here are some oscilloscope images showing the video outputs from an Atari STFM (with modulator). This is a UK model so operates to the PAL TV standard.
They show that the output on pin 2 of the Atari video connector is indeed composite video.
Also regarding the query about S-Video, well looking at these waveforms I don't think anyone is actually getting S-Video. What your equipment is probably doing is just using the information in the composite video feed (from pin 2) and ignoring the input from the "red / Chrominance" connection.
Why do I say this, well the waveforms for the red "RGB" video output from the Atari do not show the type of signal needed to correctly operate the circuitry for a chrominance input.

Thanks. This confirm what I thought. I actually looked in detail to the part of the schematics which is only installed when an RF modulator is present. And indeed the MC1377 is used to create a composite video. The cabling for s-video would be a bit different and is describe in ppera web site. In this case the luma and chroma output of the chip would be used directly (this require other changes). And yes it really does not make any sense to use the red channel for luma. As you say it is most probably ignored by the Super Color HD. It would be interesting to replace the s-video cable by a composite video and see if there is any difference.

Now a personal question on the nice pictures you have published. :)
I guess they are coming from a "PC scope" ? I am considering to buy one and would be interested to know what you have used?

I would rather have one with logic analyzer capability. I have already preselected several models: picoscope, bitscope, usbee, ...
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Re: ST to VGA - Success :)

Postby DrCoolZic » Mon Mar 22, 2010 3:17 pm

spiny wrote:MAK:

so, can I take a lead from pin 2 and a GND and I have composite video ? or am I reading it wrong ?
My 'super video box' has composite input and would presumably be better quality than the RF I'm currently using :)

good work on the traces :)


Yes this should definitively work as you have an Atari with the RF modulator. What is really confusing is that in most of the literature pin 2 is described as a composite sync output. However if you look at schematic for ST or STE you will see that when an RF is present this signal is replaced by a composite video output.

By the way this also explain the presence of a cable DIN13 to composite video found on Alison web site :)

As I do not have an Atari with MC1377 and that it seems impossible to buy one now I am looking at the GBS-8220 solution see viewtopic.php?f=15&t=17153&start=25#p162524 should receive mine any time now and hope I can make it work.

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Re: ST to VGA - Success :)

Postby spiny » Mon Mar 22, 2010 3:53 pm

DrCoolZic wrote:
spiny wrote:MAK:

so, can I take a lead from pin 2 and a GND and I have composite video ? or am I reading it wrong ?
My 'super video box' has composite input and would presumably be better quality than the RF I'm currently using :)

good work on the traces :)


Yes this should definitively work as you have an Atari with the RF modulator. What is really confusing is that in most of the literature pin 2 is described as a composite sync output. However if you look at schematic for ST or STE you will see that when an RF is present this signal is replaced by a composite video output.

By the way this also explain the presence of a cable DIN13 to composite video found on Alison web site :)

As I do not have an Atari with MC1377 and that it seems impossible to buy one now I am looking at the GBS-8220 solution see viewtopic.php?f=15&t=17153&start=25#p162524 should receive mine any time now and hope I can make it work.



neato, will fire up the soldering iron when I get home :)

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Re: ST to VGA - Success :)

Postby DrCoolZic » Mon Mar 22, 2010 4:07 pm

wongck wrote:It is written in the pin out of the Atari ST monitor that pin 2 is the composite. :mrgreen:
http://pinouts.ru/Video/AtariStMonitor_pinout.shtml

This is only true for Atari with RF modulator installed.
By the way information about Atari on the wonderful pinouts.ru site is to be taken carefully. I have noticed that for example the pinout of the FD connector is totally wrong :(

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Re: ST to VGA - Success :)

Postby Shredder11 » Mon Mar 22, 2010 4:52 pm

DrCoolZic wrote:By the way information about Atari on the wonderful pinouts.ru site is to be taken carefully. I have noticed that for example the pinout of the FD connector is totally wrong :(


So in other words whenever people like myself come across any technical schematics or diagrams on the web, we should consult those who are more informed, i.e. the good folks here on AF! :contract: :cheers:

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Re: ST to VGA - Success :)

Postby wongck » Tue Mar 23, 2010 12:03 pm

DrCoolZic wrote:
wongck wrote:It is written in the pin out of the Atari ST monitor that pin 2 is the composite. :mrgreen:
http://pinouts.ru/Video/AtariStMonitor_pinout.shtml

This is only true for Atari with RF modulator installed.
By the way information about Atari on the wonderful pinouts.ru site is to be taken carefully. I have noticed that for example the pinout of the FD connector is totally wrong :(


Well, my 520STFM.... M = modulator :wink:
And pinouts.ru is just a convenient place to point to for now bcos
back in the early 90s there was no pinouts.ru site :lol:
(Thanks for the warning)
and I use my trusty "Concise Atari ST 68000 programmer's reference guide"
as it has a page on monitor/tv output.
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Re: ST to VGA - Success :)

Postby wongck » Tue Mar 23, 2010 12:07 pm

DrCoolZic wrote:
wongck wrote:It is written in the pin out of the Atari ST monitor that pin 2 is the composite. :mrgreen:
http://pinouts.ru/Video/AtariStMonitor_pinout.shtml

This is only true for Atari with RF modulator installed.
By the way information about Atari on the wonderful pinouts.ru site is to be taken carefully. I have noticed that for example the pinout of the FD connector is totally wrong :(


For pin 2, "The Concise Atari ST 68000 programmer's reference guide" mentioned that it's a composite video, but it's reservsed for older models.
And it includes a foot note, telling not to use on older models, as it's a source of errors.
Older models... :lol: whatever that means.
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Re: ST to VGA - Success :)

Postby DrCoolZic » Tue Mar 23, 2010 12:35 pm

wongck wrote:
DrCoolZic wrote:
wongck wrote:It is written in the pin out of the Atari ST monitor that pin 2 is the composite. :mrgreen:
http://pinouts.ru/Video/AtariStMonitor_pinout.shtml

This is only true for Atari with RF modulator installed.
By the way information about Atari on the wonderful pinouts.ru site is to be taken carefully. I have noticed that for example the pinout of the FD connector is totally wrong :(


For pin 2, "The Concise Atari ST 68000 programmer's reference guide" mentioned that it's a composite video, but it's reservsed for older models.
And it includes a foot note, telling not to use on older models, as it's a source of errors.
Older models... :lol: whatever that means.

Actually there is two different topics:
1) Early Atari (the "older models") did not have any connection to pin 2 and some models (probably same old models?) had the pin 8 connected to ground.
2) "Recent models" have pin 8 connected to +12V and have either composite video OR composite sync on pin 2 (depending on RF modulator presence)

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Re: ST to VGA - Success :)

Postby wongck » Tue Mar 23, 2010 12:39 pm

DrCoolZic wrote:Actually there is two different topics:
1) Early Atari (the "older models") did not have any connection to pin 2 and some models (probably same old models?) had the pin 8 connected to ground.
2) "Recent models" have pin 8 connected to +12V and have either composite video OR composite sync on pin 2 (depending on RF modulator presence)


yes... actually "The Concise Atari ST 68000 programmer's reference guide" does mention pin 8 as well.
It said 12V on pin 8 is for SCART :mrgreen:
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Re: ST to VGA - Success :)

Postby 1024MAK » Tue Mar 23, 2010 4:17 pm

@DrCoolZic
Now a personal question on the nice pictures you have published. :)
I guess they are coming from a "PC scope" ? I am considering to buy one and would be interested to know what you have used?

I would rather have one with logic analyzer capability. I have already preselected several models: picoscope, bitscope, usbee, ...
Currently my favorite is the PoScope Mega1 Bundle for 150€ (logic analyzer part not before April) that has reasonable performance for a very attractive price.
... 2x 1MHz scope, 16x 10MHz logic analyzer, +++
Opinions, advices, ... welcome


I don't know about the 'scopes you talk about. The one I used is an old model from Pico (http://www.picotech.com)
It was a medium range unit that cost an arm and a leg many years ago, but apart from taking a while to get the trigger to lock on complex waveforms, works well for general work. The 'scopes they now have are much better.
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Re: ST to VGA - Success :)

Postby 1024MAK » Tue Mar 23, 2010 4:51 pm

For those people that have Atari computers with a modulator (eg STFM) it may be possible to get a S-Video output.
You will need to make up a custom lead.
Next week when I have some free time I will look into this some more.
For now I offer some initial thoughts, ideas and hints.
If you mix the outputs of the RGB signals (red, green and blue video feeds) then you should end up with a monochrome video feed, otherwise known as Luminance (Y - Intensity). Feed this to a S-video connector on pin 3.
For the Chrominance (C - colour) use the composite output on pin 2 of the Atari video connector and connect to the S-video connector on pin 4. Don't forget the ground (Atari pin 13 to S-Video pins 1 & 2).
Now does anyone know which signal an S-Video device uses for its sync? I suspect (and will test next week I hope) that it uses the Luminance signal line. If it will sync from the Chrominance line then we do not have a problem!
Now how to mix the RGB signals to get the Luminance signal.
Well there is more than one way. The proper method uses a resistor network and a video amplifier, but we can try the simplest method first, just using resistors.
This web page gives the general idea (but has a separate sync line): http://members.shaw.ca/novotill/RgbToMo ... /index.htm
If anyone tries this, please post any results.
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Re: ST to VGA - Success :)

Postby DrCoolZic » Tue Mar 23, 2010 6:32 pm

1024MAK wrote:Now does anyone know which signal an S-Video device uses for its sync? I suspect (and will test next week I hope) that it uses the Luminance signal line. If it will sync from the Chrominance line then we do not have a problem!

Sync and blanking are on the luma signal

cable used by Shredder (Atari - SCART - S-Video) is:
Comp Video 2 -> 20 -> 3 (Y)
Red Channel 7 -> 15 -> 4 (C)
This is strange as I would expect composite video to go to to C ?
The box must be smart to find what it needs ???


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