XEP80-II a new beginning

[tep392]

It's working!

[tep392]

Hi mytek, I need a little help.  You can probably see by the picture in my previous post that the characters are a bit under saturated.  I've adjusted contrast and brightness to their max and can't really get much improvement.  It looks sharp enough, but there is some variation in the brightness of horizontal lines across the screen.  You can best tell by looking at the tab arrows along the top of the display.  On my newer LCD, it's even more faint. So I tried the CVBS output to a different HDMI converter and had very bright letters, but that converter cuts off the first and last lines.

 

What would you suggest I check first to troubleshoot?  I have a scope, so I can check video signals if needed. Here's a photo showing the version of the HDMI converter I am using.

[+mytek]

1 hour ago, tep392 said:

What would you suggest I check first to troubleshoot?

If both the 80 column and stock 40 column video appear dim through the converter (and assuming it isn't the converter's fault) you can try increasing the value of R7 (blue circle) to see if that helps. If it is only the 80 column text that appears dim, then try removing R5 (red circle) and see if that helps. That additional attenuation by R5 was added to equalize the contrast results between the 80 column composite (CVBS) and HDMI outputs.

 

 

Since you said the 80 column output looked bright through a different converter, that could be telling of a problem with the onboard converter. Could either be defective, or there has been a manufacturer change. As you can see I had to implement white limit networks into the design because the converters I have use too much gain, perhaps that's been fixed and the white limiters are no longer required.

 

Of course one last thing that could do this is a wrong resistor value being accidentally used in at least one of those circuits. Please double check all the resistors in the video section.

 

[+videofx]

also if you have a composite input on that LCD then change the jumper on the XEP80-II TO composite and try that

[tep392]

1 hour ago, mytek said:

If both the 80 column and stock 40 column video appear dim through the converter (and assuming it isn't the converter's fault) you can try increasing the value of R7 (blue circle) to see if that helps. If it is only the 80 column text that appears dim, then try removing R5 (red circle) and see if that helps. That additional attenuation by R5 was added to equalize the contrast results between the 80 column composite (CVBS) and HDMI outputs.

 

 

Since you said the 80 column output looked bright through a different converter, that could be telling of a problem with the onboard converter. Could either be defective, or there has been a manufacturer change. As you can see I had to implement white limit networks into the design because the converters I have use too much gain, perhaps that's been fixed and the white limiters are no longer required.

 

Of course one last thing that could do this is a wrong resistor value being accidentally used in at least one of those circuits. Please double check all the resistors in the video section.

 

This is very helpful.  For a quick test, I clipped R5, and the characters were much brighter, but the background is now more grey than black. The Atari passthrough video looks fine.  I'll try playing around with the value of R5 a bit. Thank you!

[_The Doctor__]

is R6 part of the balancing act as well, yes?

also consider R5 will need a value to keep from going too far the other way, try adjusting your display so it works for all your other stuff and once satisfied reconnect your Atari and use a variable resistor to fine tune the Atari XEP II to work nicely remove the variable resistor or decade resistance box and read the value... put that resistor in and share your findings for the rest of us please!

 

edit I see you've discovered some of this already...

Edited November 30, 2021 by _The Doctor__

[tep392]

I can't freaking believe it. I just checked the value of R5, and it's 43 ohms.  I ordered two 430's from Digikey and they gave me a package with one 430 and one 43.  Under bright light, it is clearly a black stripe on the 43 ohm. I'll try the correct 430 and see how it looks.

 

Edit:  Using the correct 430 ohm resistor fixed it.  DIGIKEY!!!!!!!

[_The Doctor__]

This happens more often than you think, we had people meter out components before they made the production kits up for the line. You never really know what you are going to get sometimes and it isn't always easy to see the bands on stuff these days. SMD components can be a pain as well.

Glad to see you found it !

Hopefully it won't be too long before replacement can be done. Congrats on a mostly drama free build!

[tep392]

It's fixed.

[+mytek]

46 minutes ago, tep392 said:

I can't freaking believe it. I just checked the value of R5, and it's 43 ohms.  I ordered two 430's from Digikey and they gave me a package with one 430 and one 43.  Under bright light, it is clearly a black stripe on the 43 ohm. I'll try the correct 430 and see how it looks.

 

Edit:  Using the correct 430 ohm resistor fixed it.  DIGIKEY!!!!!!!

Good find ?

 

14 minutes ago, tep392 said:

It's fixed.

Nice

 

Glad you figured it out. BTW, I think you are now the 3rd person to have a working XEP80-II in their possession (assuming everyone else reported in)

 

Don't forget to download some of the other goodies, such as the patched version of AtariWriter 80 (here).

 

[tep392]

1 hour ago, mytek said:

Good find ?

 

Nice

 

Glad you figured it out. BTW, I think you are now the 3rd person to have a working XEP80-II in their possession (assuming everyone else reported in)

 

Don't forget to download some of the other goodies, such as the patched version of AtariWriter 80 (here).

 

Thank you very much for steering me in the right direction.    And a huge thanks for developing this.  It's a great addition to my system.  Now I just need to get a dot matrix printer so I have a complete setup.  

 

[tep392]

2 hours ago, _The Doctor__ said:

is R6 part of the balancing act as well, yes?

also consider R5 will need a value to keep from going too far the other way, try adjusting your display so it works for all your other stuff and once satisfied reconnect your Atari and use a variable resistor to fine tune the Atari XEP II to work nicely remove the variable resistor or decade resistance box and read the value... put that resistor in and share your findings for the rest of us please!

 

edit I see you've discovered some of this already...

The variable resistor for R5 is a good idea.  I may just put one in permanently so I can fine tune it if needed.

[+Larry]

Probably a dumb question, but... I presume your regular resistor has two connection points, but a variable resistor has three, including a ground.  How will you wire it?  Jumper wire to ground?

[_The Doctor__]

17 minutes ago, Larry said:

Probably a dumb question, but... I presume your regular resistor has two connection points, but a variable resistor has three, including a ground.  How will you wire it?  Jumper wire to ground?

you tie the center and low side leg together and wire it in series with a protection resistor so you don't short to ground when going full scale in either direction.

[+videofx]

Thats why I use my component tester before installing

[gwpt]

Hi all, is there any reason this wouldn't work if I have a Sophia 2 installed? thx

[+mytek]

1 hour ago, gwpt said:

Hi all, is there any reason this wouldn't work if I have a Sophia 2 installed? thx

It's completely separate. Think of this as simply another video card. So yes it will work.

 

[Mathy]

Hello guys

 

8 hours ago, mytek said:

It's completely separate. Think of this as simply another video card. So yes it will work.

 

But the signal from the Sophia(2) can not be fed into the XEP80(-II).

 

Sincerely

 

Mathy

 

 

[+mytek]

7 hours ago, Mathy said:

But the signal from the Sophia(2) can not be fed into the XEP80(-II).

Good point, but I also wasn't suggesting that it could be. Sophia is also an independent video device, and should be thought of as such. It does not eliminate the original Atari video output, which is what the XEP80-II board can and will accept for conversion to HDMI if the user has opted to include the AV2HDMI converter as part of that.

 

The main point I was trying to make, is that the XEP80 or the XEP80-II should be thought of as independent video output devices, and are not affected by what other video devices you may have installed in your Atari (e.g., Sophia or VBXE).

 

However Mathy brings up a very good point as well, that people need to be aware that they are not going to be able to use the XEP80-II's built-in video switching and AV2HDMI provisions to channel other video sources through it, other than the stock Atari video or the output of a UAV converted system. Your Sophia(a,b,c,2) or your VBXE cannot be somehow channeled through the XEP80-II unless you do some very creative modifications to it (I shudder to think of what that might look like ).

 

Although if someone wanted to take that on, the schematics for the XEP80-II are in the public domain, and with a new PCB design there's no reason why a Sophia with DVI capabilities couldn't be accommodated by a more sophisticated or additional video switching circuit, and that other AV2HDMI converters such as the RetroTink couldn't be used on the Atari stock video and/or XEP80 composite signals. All it takes is the willingness and smarts to make it happen

 

Edited December 1, 2021 by mytek

[tep392]

I've been having fun playing with the XEP80-II.  There are some interesting demo's on the XEP80 boot disk.  They don't all work though.  The Altirra driver makes a huge difference in the speed printing to screen.  I also just picked up a 1025 printer.  Not as nice as an Epson, but I wanted to keep it Atari.  I started a game project a few years ago on my 800 with the intention of developing completely on the 8-bit.  Now that I have the 80 column display and printer, I'm in a good position to continue it.

[_The Doctor__]

What doesn't work? that's important.

They work on the original?

[tep392]

1 minute ago, _The Doctor__ said:

What doesn't work? that's important.

They work on the original?

The graphics demo and the window demo didn't work for me.

[+mytek]

2 hours ago, tep392 said:

The graphics demo and the window demo didn't work for me.

Never tried that myself. Really didn't give it much thought since everything I remember reading about the graphics side of things was not worth worrying about due to its severe limitations. Bottom line is why do what can be done better on the Atari side. The real strength of the XEP80 is spelled out pretty clearly in its name "80 Column Text". This isn't a VBXE after all

 

But seriously 320x200 monochrome graphics at the speed of a snail and only displaying on 1/2 the screen... I don't think that'll be missed. But just out curiosity I wonder why it doesn't work? Something I'll look into when time permits.

 

First XEP80 Slide Show ::: ANTIC VOL. 7, NO. 6 / OCTOBER 1988

Quote

With the XEP80 handler installed, Graphics 24 (8 X16) has a very special meaning. It kicks the XEP80 into a 320 X 200 bit image graphics mode, virtually identical in bit-mapping to the standard Graphics 8 display. However, you cannot PLOT and DRAWTO on the XEP80 display. Graphics 8+16 for the XEP80 places the device into "burst mode;" where every byte of data received is treated as eight pixels of display information. It is mapped directly to the XEP80's 80-column screen and the cursor is bumped to the next eighth pixel position.

 

A graphics demo provided by Atari on the XEP80 boot disk requires five minutes to slowly draw a circle on the top quadrant of the screen display. This slowness is extremely misleading. To see just how fast the XEP80 display can be filled with graphics, type in Listing 1, XEPLIST1.BAS, check it with TYPO II and SAVE a copy before you RUN it.

 

This first program fills a 40-byte string with ASCII values 255 to 0, stepping backwards. Each graphics "line" is then "plotted" on the XEP80's display simply by printing it. It's slow compared to how quickly a standard Graphics 8 display can be filled, but it is still pretty quick and we can go even faster. Try changing the SZ variable in line 10 to different values, up to 8000, a full screen on the XEP80 display.

 

Using this first demo program, you will notice that the fill screens wrap around on themselves from bottom to top. While developing the XEP80 Slide Show program, I tried printing a 7680-byte graphics mode screen (192 lines) to the XEP80, immediately followed by 32 zero bytes (eight more lines). Then I loaded and printed the next graphics screen. It wrapped around to the top of the display as I expected, but was slightly skewed to the left.

 

I discovered that an additional 32 zero bytes had to be sent to the XEP80 to get a perfect wraparound from bottom to top. This made for an interesting slide show, continuously playing one picture after the next. However, the XEP80 always got skewed again at seemingly random intervals.

 

Apparently in graphics burst mode the timing is very critical between the computer and the XEP80. Eventually it will lose a byte or two. With no special handshaking in burst mode to detect and correct such errors, your pictures will be skewed again. Currently the only way I know to get things synchronized between the computer and the XEP80 is to issue the OPEN command to E:, which forces the text mode and normal communications.

 

Edited December 2, 2021 by mytek

[+mytek]

Well I did check out the graphics and window demo, and it did indeed fail to run them properly.

 

But the DEMO80.BAS runs perfect, even under Altirra Basic and with Avery's Ultraspeed Driver.

 

BTW, this has not been accelerated after the fact. What you see is in Real Time.

 

 

DEMO80.atr

 

Can't explain why those other demos failed, but from a purely 80 column text mode everything appears solid. In my book Mission Accomplished because that really was the goal of the project, as well as being able to use a modern LCD to display it.

 

However for those that enjoy waiting an incredibly long time to view a 1/2 screen at graphics mode 8 or want to pan a window of text around the screen, I guess this is a Fail. So currently if that's what you need, I wouldn't recommend buying or building the XEP80-II

 

Maybe in the future this can get resolved.

 

Edited December 3, 2021 by mytek

[+mytek]

Aww the WINDOW Demo does work ?

 

It requires that the XEP80-II be plugged into Joystick port #1, and the joystick in port #2.

 

 

So apparently the only mode not working would be the graphics 8 one.