XEP80-II a new beginning

[+mytek]

Because I don't want to derail the "Altirra 3.90 released" topic more than I have already, I have started a new one. Please post any inquiries about this new project over here.

 

I began a new project recently to resurrect the original Atari XEP80 in a much smaller form factor, and to allow for an inexpensive AV-to-HDMI off the shelf daughter board option to be used for a more universal video output. I have called this project the XEP80-II.

 

 

 

 

 

Preliminary Specifications

• B&W 80 Column x 24 Line Text Display (via analog composite output with option to support 3rd party HDMI converter)
• Serial 2-wire Communications Interface via Atari Joystick Port (same as original XEP80).
• Power via same Joystick Port.
• All chips besides NS405 Display Controller to be low power CMOS.
• Original ROMS replaced with EEPROMS.
• Firmware ROM split into two parts for NTSC and PAL specific versions selectable by jumper (for corrected timing parameters).
• Adjustment to Video Output to render a more standardized signal and to better position the beginning of each line.
• Board Footprint: 3.10" x 3.10" (78.74 mm square).
• No Parallel Printer Port

 

Check out the: XEP80-II Blog Post

 

Edited June 25, 2021 by mytek
Fixed CVBS Output Labeling

[Lord Thag]

This is the #1 thing I want/need for my 8-bits. I'm not willing to muck with VBXE and it's non NTSC monitor requirements, much as I wish there was an NTSC version.

 

I'd love a simple interface that doesn't require soldering, and which I can just swap between my different Ataris, and which works with typical off the shelf monitors. I use SDX and Last Word as a kind of distraction free writing thing, as well as some light coding, and doing so at 80 columns would be amazing. Not having something like this has been my biggest frustration with the hardware scene. I'll definitely be getting one of these when you're ready to sell. Thanks for taking this on!

[+mytek]

1 minute ago, Lord Thag said:

I'll definitely be getting one of these when you're ready to sell. Thanks for taking this on!

You're very welcome, but it will be a while before this will be ready for prime time. I still have to verify my schematics are accurate, finish the board layout, have samples made and test, plus there are details related to the firmware mods that need to be worked out. But when its all done this will see a public release of the gerber files for PCB manufacture, and TBA will be the first produced source assuming there is a demand for it.

[+videofx]

Thanks! Look forward to getting one!  I am curious how the video in gets connected

[gilsaluki]

Ears perked.

[+MrFish]

1 hour ago, mytek said:

• Board Footprint: 3.10" x 3.10" (78.74 mm square).

 

Calling @Mr Robot...

 

[+mytek]

29 minutes ago, videofx said:

Thanks! Look forward to getting one!  I am curious how the video in gets connected

Male RCA pigtail.

 

As can be seen in my prototyping set-up.

[Mathy]

Hello Michael

 

Thanks for starting a new thread.  I wasn't following the Altirra thread, as Altirra won't run natively on a Mac, so I missed what you said about this over there.

 

Am I right in assuming that the off the shelf daughterboard is the only output on the XEP80-II?

Would you or are you considering including both upgrades mentioned here?

 

Sincerely

 

Mathy

 

 

 

[+DrVenkman]

I love this plan and I’m excited to be a part of it!

 

Or, at least, a part of watching it.  

[danwinslow]

Love this. Will buy.

[+mytek]

44 minutes ago, Mathy said:

Am I right in assuming that the off the shelf daughterboard is the only output on the XEP80-II?

The analog composite output could still be used without the HDMI daughter board.  EDIT: due to a mis-labeled CVBS jack shown on the PCB example photos which I just now discovered, there was some confusion about this. I have now corrected the board images by removing the 'IN' designation that was incorrectly applied. Sorry about that.

 

44 minutes ago, Mathy said:

Would you or are you considering including both upgrades mentioned here?

Aww yes the TTL related mods. I wasn't planning on it, after all those monitors are getting to be very rare, and this revised release was really aimed at facilitating more modern and readily available TVs. Thanks to @phaeron's XEPVHOLD revised Display Timing Parameters this has now been made possible, and I'm shooting to incorporate those into the firmware ROM image so that even old programs such as AtariWriter 80 will still work out of the box.

 

I know BITD modding the XEP to feed a TTL monitor was deemed as the absolute best display for the 80 column text. However it looks pretty friggin good via the AV2HDMI converter as can be seen below.

 

(click on image to enlarge for full effect)

 

[Atari8guy]

Just a question, the XEP will do a 25th line.  VT850 (for example) uses this line as a status line.  Will this version?

 

 

[+x=usr(1536)]

2 hours ago, mytek said:

I began a new project recently to resurrect the original Atari XEP80 in a much smaller form factor, and to allow for an inexpensive AV-to-HDMI off the shelf daughter board option to be used for a more universal video output. I have called this project the XEP80-II.

Interesting timing - I've been experimenting with various off-the-shelf Chinese composite-to-HDMI adapters in order to use the XEP80 with a modern LCD recently.  So-so is about the best description I can give of how well that's been going; there's a surprising amount of variance between units even when it's clear that they're basically the same.

 

Definitely going to keep an eye on this one; having an external 80-column solution that works across A8s is something I've been interested in for some time.

[+mytek]

8 hours ago, 8bitguy1 said:

Just a question, the XEP will do a 25th line.  VT850 (for example) uses this line as a status line.  Will this version?

It'll do whatever a stock XEP80 is capable of with the stock ROM code which is available online at Sobola's website (scroll down the page). However with the new timing parameters there are only the 24 lines that I can see, and if the cursor is on the 24th line, moving one more down puts you at the first line at the top of the screen, so apparently the 25th line was sacrificed from what I'm seeing.

 

Speaking of which, @phaeron do you have the original parameters that are in the Atari XEP firmware?

 

This is what I see in your XEPVHOLD file.

 

I'm trying to find where these are initialized in the XEP's firmware ROM, so it would be a great help to know what they are presently, in order to make searching for them a bit easier. Because I can't make heads or tails where this is happening in the disassembly I did from the binary 8048 file.

 

[+Nezgar]

Pretty sweet... Dreaming of features here... Monitor passthrough, and a switch/button to toggle between Atari native video, and XEP video.. or a 3rd mode to genlock them together? ?  DIN5 in, RCA jacks for Composite, Audio + S-Video out...

 

(I don't know enough about Genlock to know if this is even remotely possible, since the XEP80 video signal is well known to be very off-spec)

 

Edit: I guess single-monitor video switching is easily solved by a common video switcher... or a monitor with multiple inputs like a C1702

[jaybird3rd]

Glad to see you're working on this!  (I was toying with the idea of doing this myself at some point.)

 

Question: The original XEP-80 used the NS405-A12N, but the NS405-B12N is much more readily available.  Will the -B work with the new board, or will it be necessary to stick with the -A?

[Mazzspeed]

So this is a re implementation of the XEP-80 without the issues of the XEP-80?

 

Sounds cool, I'd be interested in one of these.

[+DrVenkman]

6 minutes ago, Nezgar said:

Pretty sweet... Dreaming of features here... Monitor passthrough, and a switch/button to toggle between Atari native video, and XEP video.. or a 3rd mode to genlock them together? ?  DIN5 in, RCA jacks for Composite, Audio + S-Video out...

 

(I don't know enough about Genlock to know if this is even remotely possible, since the XEP80 video signal is well known to be very off-spec)

 

Edit: I guess single-monitor video switching is easily solved by a common video switcher... or a monitor with multiple inputs like a C1702

Feature-creep is not @mytek's style. He wants a better, more compatible XEP80, but in a smaller form factor. The little HDMI converter board add-on is probably the most you're gonna get in terms of "extras" over the original.  

[jaybird3rd]

8 minutes ago, DrVenkman said:

Feature-creep is not @mytek's style. He wants a better, more compatible XEP80, but in a smaller form factor. The little HDMI converter board add-on is probably the most you're gonna get in terms of "extras" over the original.  

I agree, feature creep is fatal.  Better to keep the features to a minimum.  It would be nice if the DB25 printer port from the original could be retained, even if only as a pin header, but I can understand the decision to leave it out.

[+mytek]

48 minutes ago, x=usr(1536) said:

Interesting timing - I've been experimenting with various off-the-shelf Chinese composite-to-HDMI adapters in order to use the XEP80 with a modern LCD recently.  So-so is about the best description I can give of how well that's been going; there's a surprising amount of variance between units even when it's clear that they're basically the same.

I use one of these that I got off eBay. Haven't tried this Amazon one yet, but I will.

 

 

 

The thing is none of these Chinese converters are necessarily great at dealing with the color video coming out of the Atari, but the XEP80's monochrome signal with phaeron's XEPVHOLD parameters applied is a simpler signal to deal with. I'll be trying a few more converters, but I suspect it'll be pretty consistent in this usage. BTW, I'm assuming you've applied the following file after loading the XEP80 driver?

XEPVHOLD.COM

 

I also had to alter the stock HSYNC delay which is controlled by C31 on the XEP80 PCB. With the stock capacitor value of 0.01uf it still lets a bit of the last character spill off the right edge of the screen. By adding a bit more capacitance in parallel, I was able to center up the image and get all 80 characters to display (add in .001uf increments).

 

 

I also had to tweak the VHOLD parameters a tiny bit to stop the 24th line from repeating at the bottom of the screen (only saw the very top part ghosting). Here's my modified program based on that change.

XEPVHLD1.COM

 

[+mytek]

8 hours ago, Nezgar said:

Pretty sweet... Dreaming of features here... Monitor passthrough, and a switch/button to toggle between Atari native video, and XEP video.. or a 3rd mode to genlock them together? ?  DIN5 in, RCA jacks for Composite, Audio + S-Video out...

 

(I don't know enough about Genlock to know if this is even remotely possible, since the XEP80 video signal is well known to be very off-spec)

 

Edit: I guess single-monitor video switching is easily solved by a common video switcher... or a monitor with multiple inputs like a C1702

See DrVenkman's post (also quoted at the end of this post). He pretty well sums up my modus operandi. So in other words I'm keeping this one simple.

 

As for Genlocking. That would be very tricky indeed. I did try some experiments at possibly getting one color to work (the background), but had to give up on that when it became apparent that full Genlocking would be required even for that seemingly simple requirement. Then there's the issue with trying to do color over a composite output mixed with tiny text - probably be too much fringing and such to make it worth it. The NS405 data sheet does show a method of producing RGB, but it gets very complicated, very quickly when all things are considered.

 

Bottom line is I want this to be cheap in cost (not in quality).

 

8 hours ago, jaybird3rd said:

Glad to see you're working on this!  (I was toying with the idea of doing this myself at some point.)

 

Question: The original XEP-80 used the NS405-A12N, but the NS405-B12N is much more readily available.  Will the -B work with the new board, or will it be necessary to stick with the -A?

I picked up 200 pulled chips that were a mixture of NS405-B12N and NS405-B18N. They all work as is in the original XEP80. The difference has to do with whether they have onboard ROM or not. Since the XEP was based on a ROM-less version (NS405-A12N) either works. It was because of that acquisition ($40 for 200 NS405 chips), that really got me looking at this XEP re-creation.

 

8 hours ago, Mazzspeed said:

So this is a re implementation of the XEP-80 without the issues of the XEP-80?

Yes

 

8 hours ago, DrVenkman said:

Feature-creep is not @mytek's style. He wants a better, more compatible XEP80, but in a smaller form factor. The little HDMI converter board add-on is probably the most you're gonna get in terms of "extras" over the original.  

Affirmative ?

 

[Mathy]

Hello guys

 

After Michael finishes the XEP80-II somebody else could come up with XEP80-III with "feature creep deluxe" and untie the cheetahs legs.      (not me!)

 

Sincerely

 

Mathy

 

 

[jaybird3rd]

12 minutes ago, mytek said:

I picked up 200 pulled chips that were a mixture of NS405-B12N and NS405-B18N. They all work as is in the original XEP80. The difference has to do with whether they have onboard ROM or not. Since the XEP was based on a ROM-less version (NS405-A12N) either works. It was because of that acquisition ($40 for 200 NS405 chips), that really got me looking at this XEP recreation.

Yes, I think I know the exact source you're referring to, and that's what got me thinking as well!  (I picked up 100 of those chips myself with the idea of doing my own recreation someday, but I'm more than happy that you got to it first.  I already have another project in mind for mine.)

[+mytek]

46 minutes ago, jaybird3rd said:

I agree, feature creep is fatal.  Better to keep the features to a minimum.  It would be nice if the DB25 printer port from the original could be retained, even if only as a pin header, but I can understand the decision to leave it out.

In this day and age the printer port isn't all that useful. Even BITD of printers that supported this, I heard it didn't work all that reliably, and crippled the 80 column update as well. Sometimes you've got to stick to the main target and resist adding bells and whistles   Now days we have APE, RespeQT, and Fujinet for printing to our PCs, with Fujinet giving us full emulation of every printer ever made.

 

4 minutes ago, jaybird3rd said:

Yes, I think I know the exact source you're referring to, and that's what got me thinking as well!  (I picked up 100 of those chips myself with the idea of doing my own recreation someday, but I'm more than happy that you got to it first.  I already have another project in mind for mine.)

Yep that's most certainly the same source. MacRorie also picked up some as well. Too bad these weren't Pokeys.

 

17 minutes ago, Mathy said:

After Michael finishes the XEP80-II somebody else could come up with XEP80-III with "feature creep deluxe" and untie the cheetahs legs.      (not me!)

Not me either

[Mathy]

Hello jaybird3rd

 

11 minutes ago, jaybird3rd said:

I already have another project in mind for mine.

 

Damn, now I'm curious...

 

Sincerely

 

Mathy