1088XEL Atari ITX Motherboard DIY Builders Thread

[+mytek]

6 hours ago, LarryL said:

Works like a charm

 

first action: flashing U1MB

 

You're getting so good at this that @MacRorie might need to hire you

 

Nice to see these boards are still being DIY assembled by individuals - the 1088XEL is coming up on 5 years since inception.

[+LarryL]

3 hours ago, mytek said:

 

You're getting so good at this that @MacRorie might need to hire you

 

Nice to see these boards are still being DIY assembled by individuals - the 1088XEL is coming up on 5 years since inception.

Thanks ? 

(un)fortunately, I already have a job  

is it really already 5 years???

[+mytek]

33 minutes ago, LarryL said:

is it really already 5 years???

Yep, the project officially began in January of 2017.

 

 

And the gerbers for DIY were released to the public exactly 9 months later in October 2017.

 

 

And here's the first one I built based on those gerbers, which I still have, and still works.

 

 

Edited December 4, 2021 by mytek

[+DrVenkman]

11 minutes ago, mytek said:

And the gerbers for DIY were released to the public exactly 9 months later in October 2017.

 

I was not part of Michael's beta team for the XEL, but I did get my boards from MacRorie on October 31, 2017.

 

 

Once I started getting all the rest of my parts ordered and in-hand, began assembly in late December. 

 

 

Building that system was sort of a "gateway drug" for me - learned a lot, had a great time doing it, and ended up with an awesome machine.

 

[+LarryL]

Ready ? 

 

 

mounting the board inside the case, and making all the internal cables and mountings took some time today

 

But I must say: I really love the result! 
 

[john_q_atari]

I was looking through the 1088xel schematic and BOM today as I was thinking of using parts of the circuit in one of my projects. I noticed that the NDP6020P used in the power supply design is now obsolete and no longer available through US distributors like Digikey and Mouser. While looking through the datasheets it seems like the IRF4905 might make a good substitute. Mouser #:
942-IRF4905PBF  https://www.mouser.com/ProductDetail/Infineon-IR/IRF4905PBF?qs=9%2BKlkBgLFf39l0HsWdxvdw%3D%3D 

@mytek

 

For your push on push off power circuit, any reason the LM555 was chosen instead of the NE555?

[+mytek]

17 hours ago, john_q_atari said:

I was looking through the 1088xel schematic and BOM today as I was thinking of using parts of the circuit in one of my projects. I noticed that the NDP6020P used in the power supply design is now obsolete and no longer available through US distributors like Digikey and Mouser. While looking through the datasheets it seems like the IRF4905 might make a good substitute. Mouser #:
942-IRF4905PBF  https://www.mouser.com/ProductDetail/Infineon-IR/IRF4905PBF?qs=9%2BKlkBgLFf39l0HsWdxvdw%3D%3D 

That looks like a reasonable substitute. I think I even substituted some SOT223 devices i had on hand by standing them upright and then soldering them to the pads (they have the same lead spacing and electrical connections).

 

17 hours ago, john_q_atari said:

For your push on push off power circuit, any reason the LM555 was chosen instead of the NE555?

The 555 is generic, so any variant will work just fine, including the one you specified ?

 

[Thelen]

I'm trying to get my XEL1088 to work, but it doesn't ? Looks like the oscillator circuit doesn't do a thing (when I measure on the OSC jumper pins there is no signal (I'm using a scope for the first time in 20 years- and i compared it with an 800xl where i see 'a frequency' on the oscillator pins).When i press the power on button there happens something for a split second and then there's nothing...

Are there maybe any tips about this, or maybe a schematic about the oscillator circuit for the 1088?

Thanks! ?

[+mytek]

37 minutes ago, Thelen said:

Are there maybe any tips about this, or maybe a schematic about the oscillator circuit for the 1088?

The schematic covering the entire unit can be found at my website (link in my signature). The oscillator circuit used in the XEL is pretty much a straight copy from Atari, and can even use the same transistors, although I picked some newer ones. If it's not oscillating best place to start would be to get out the magnifier and check the solder joints looking for open or bridged connections. And lastly make sure all the resistors, capacitors. and transistors are the correct values. Basically verify that everything is the same as shown in the schematic.

 

After making sure all is good from a visual perspective, run a transistor test (most meters have this or a diode checking facility), because there really isn't much else that would fail or be defective in that circuit.

 

Edited January 28, 2022 by mytek

[Thelen]

18 hours ago, mytek said:

The schematic covering the entire unit can be found at my website (link in my signature)

 

Thanks! Earlier I looked at the schematics, but now I found the schematic ?. After checking every trace, soldering and component from the oscillator circuit I found out that I used for R39 a 6K8 resister.. Very strange, must have been sleeping....changed it to the 430R, checked on the oscilloscope - and yes, signal!



And I didn't expect it to work after just making one mistake, but it did!! Fantastic, I'm very happy with the result so far..! Thanks for helping me, and creating this great project!

[+mytek]

14 minutes ago, Thelen said:

And I didn't expect it to work after just making one mistake, but it did!! Fantastic, I'm very happy with the result so far..! Thanks for helping me, and creating this great project!

I'm glad it was that easy to fix 

 

The schematic for this board as well as my other released projects is very accurate since the PCB layout was done directly from it, and the parts specified were proven to work in beta testing by multiple builds.

 

Enjoy.

 

Edited January 29, 2022 by mytek

[+mytek]

Builder Alert for 1088 Series Boards

After being nearly non-existent for months, these chips are now back in stock at a few places, with Newark looking like the best bet. Not sure how long that'll hold true, since these chips apparently find use in the automotive industry as well.

 

 

 

EDIT: the PIC12F1572 can take the place of the spec'ed PIC12F1571 in the XEL by using the firmware flashers for the 1088XLD.

 

Edited January 29, 2022 by mytek

[Thelen]

Maybe someone can give me another hint ? The PM graphics are looking messed up (as in the photo underneath) I did some testing, swapped GTIA, Antic and looked at the soldering- but before I spent all day searching, is there something specific to look why the PM is going wrong?

 

Also, as you can see in the picture, the screen has 'zigzag' lines...(I haven't yet done any research on it) ?

[+mytek]

4 hours ago, Thelen said:

Maybe someone can give me another hint ? The PM graphics are looking messed up (as in the photo underneath) I did some testing, swapped GTIA, Antic and looked at the soldering- but before I spent all day searching, is there something specific to look why the PM is going wrong?

When I've seen this happen in the past, it's usually been attributable to problems with having insufficient buffering and/or too much delay in that circuit associated with the Phi2 clock, and is usually more the case for PAL than NTSC. On the XEL the chip to look at would be U11 (74F08). If it's not actually a 74F series IC, then it needs to be changed for one - HC or HCT or even LS won't do it.

 

Edit: my post addresses the PMG problem. Not sure what's causing the zig-zag lines.

 

Edited February 3, 2022 by mytek

[+Stephen]

6 hours ago, Thelen said:

Also, as you can see in the picture, the screen has 'zigzag' lines...(I haven't yet done any research on it)

I assume you have a PAL system.  I have noticed on every PAL Atari I have, those zig-zag lines are present, and the NTSC systems do not do this.

[Thelen]

4 hours ago, mytek said:

When I've seen this happen in the past, it's usually been attributable to problems with having insufficient buffering and/or too much delay in that circuit associated with the Phi2 clock, and is usually more the case for PAL than NTSC. On the XEL the chip to look at would be U11 (74F08). If it's not actually a 74F series IC, then it needs to be changed for one - HC or HCT or even LS won't do it.

 

 

Thanks for thinking with me. U11 is a 7408 (I hoped I did use a wrong 74... but I didn't ? ). When ordering all the parts, I couldn't order a 27ohm R35, so I took the closest I had, and for this one used a 26,7ohm resistor. Could that be a problem?

 

2 hours ago, Stephen said:

I assume you have a PAL system.  I have noticed on every PAL Atari I have, those zig-zag lines are present, and the NTSC systems do not do this.

Yes, indeed, it's PAL... Since the new Atari videocircuits and displays are getting better than in the 80's&90's (RF and composite) - we can see too much ?

Edited February 3, 2022 by Thelen

[Thelen]

1 hour ago, Thelen said:

Thanks for thinking with me. U11 is a 7408

I'm sorry forgot the F... meant a 74F08

[+mytek]

1 hour ago, Thelen said:

I'm sorry forgot the F... meant a 74F08

Sometimes I've also noticed the manufacturer of the IC making a difference. Did you use the one specified in the BOM?

 

Digi-Key P/N: 296-3543-5-ND

 

And of course there is always the chance that you have a defective chip that doesn't live up to its intended specification, so swapping for a new one might be warranted.

 

[+Stephen]

I will say that I had GTIA issues when I built my initial prototype 1088XEL.  Changing out U11 is what eventually got the machine working.  I had a similar symptom - GTIA was fetching incorrect data.  Oddly, I don't believe any of the NTSC users had this issue.

[Thelen]

Thanks again, both! No, I didn't use exactly that one.. (and I can't order 1 from them, shipping to the Netherlands is $22 ? ) I Will do a search if I can get one here ?

 

[Thelen]

Found one and ordered!

[Panther]

I didn't find any info on this, so after figuring out the connection I figured I'd share it.  If you wish to connect an XEL-CF3 and use only one PS/2 keyboard, you can do the following to get the Alt-N (Next Disk) function working from the TK-II:

Remove diode D1 next to U7 (the TK-II PIC16F1847).

Connect J25 (PS2-Aux) pin 4 (next to the PS/2 connectors) to pin 2 of the STATS connector of the XEL-CF3 board.

 

[+mytek]

9 hours ago, Panther said:

I didn't find any info on this, so after figuring out the connection I figured I'd share it.  If you wish to connect an XEL-CF3 and use only one PS/2 keyboard, you can do the following to get the Alt-N (Next Disk) function working from the TK-II:

Remove diode D1 next to U7 (the TK-II PIC16F1847).

Connect J25 (PS2-Aux) pin 4 (next to the PS/2 connectors) to pin 2 of the STATS connector of the XEL-CF3 board.

Bravo you found the Easter Egg ?

 

So what @Panther did by removing the diode, was to circumvent a test that TK-II does on power-up to see if the hardware supports dual PS/2 keyboards. When that test fails, it assumes that it's being used in a 1088XLD and repurposes the two extra I/O bits of the PIC chip that would have normally been used for the 2nd PS/2 port's clock and data, and then converts them into a multiplexed function that can control which joystick port will be the mouse, as well as perform the disk swap function. To get the full functionality usually requires a dual NAND Gate (HCT00) to combine the two individual I/O pins into the single swap output, but as can be seen that extra bit of logic can be omitted when only the swap feature is needed (quite ingenious of @Panther to discover that).

 

EDIT: my only concern with this method of providing a keyboard activated swap button is that those two extra PIC I/O lines which are shown as JOY1 and JOY2 on the XLD schematics, normally sit at a logic low state. Whereas the swap button input on the XEL-CF3 board has an inactive state of a logic high via a 1k pull-up resistor, and needs a transition from logic high to logic low to perform the swap - just the opposite of the JOY1 and JOY2 lines which both go high for only a moment when pressing ALT+N, and then drop back to their latched state. Because the XLD uses a NAND gate on those two pins, this changes that momentary high on both pins to a momentary low for the swap. And if I recall correctly, having the swap input always resting at a logic low state can cause some potential problems with the U1MB, which unfortunately I forget the exact symptoms. Something else to keep in mind is by repeatably pressing ALT+J will result in stepping the JOY1 and JOY2 lines through their 3 possible states for mouse port selection, and is a latched non volatile function. Anyway I mention all this in case you are seeing any aberrant behavior with your implementation.

 

Check out the 1088XLD Schematic to see the full implementation.

 

And here's the 1088XEL Schematic and the XEL-CF Drive Schematic as reference, to see the TK-II PS/2 AUX and CF3 STATS header pins defined.

 

On the stand-alone TK-II-PBJ PS/2 Pokey piggyback board there are also 3 available pins broken out to the header specified as /AUX1, /AUX2, /AUX3 that can be used in a similar way. They normally sit at a high logic state, but individually go low responding to ALT+1, ALT+2, or ALT+3. All three act like a momentary push button switch connected to GND, being triggered by these hot key presses..

 

Edited February 5, 2022 by mytek
Added note

[Panther]

2 hours ago, mytek said:

Bravo you found the Easter Egg ?

 

Thank you for the great feature!  I bought my 1088XEL components four years ago, but wasn't able to assemble it at the time (I was recovering from a serious injury), and finally got to it two weeks ago.  I realized though that I had an earlier XEL-CF version that did not have the disk swap, so I ordered components and boards for it.  While waiting for them to arrive I decided to assemble the 130XE Remake board from Santos that I had here as well and then was messing with the TK-II on that when I saw that it it supported the Alt-N function.  Yesterday my XEL-CF3 boards arrived from Oshpark and I just had to have that Alt-N function working.  Now my 1088XEL is configured perfectly for me.

[Panther]

On 2/5/2022 at 8:21 AM, mytek said:

EDIT: my only concern with this method of providing a keyboard activated swap button is that those two extra PIC I/O lines which are shown as JOY1 and JOY2 on the XLD schematics, normally sit at a logic low state. Whereas the swap button input on the XEL-CF3 board has an inactive state of a logic high via a 1k pull-up resistor, and needs a transition from logic high to logic low to perform the swap - just the opposite of the JOY1 and JOY2 lines which both go high for only a moment when pressing ALT+N, and then drop back to their latched state. Because the XLD uses a NAND gate on those two pins, this changes that momentary high on both pins to a momentary low for the swap. And if I recall correctly, having the swap input always resting at a logic low state can cause some potential problems with the U1MB, which unfortunately I forget the exact symptoms. Something else to keep in mind is by repeatably pressing ALT+J will result in stepping the JOY1 and JOY2 lines through their 3 possible states for mouse port selection, and is a latched non volatile function. Anyway I mention all this in case you are seeing any aberrant behavior with your implementation.

I looked over everything again and I do see that the Mousetari PIC is connected to the output and then to the Joy1 indicator, which the 1088XEL lacks.  I've had no trouble at all with the line being connected directly from the TK-II on my 1088XEL, but when I attempted the same thing on another one it did in fact freak out the U1MB.  Perhaps I happened to get lucky on the one system and the U1MB just isn't picky.  Time to see if there are any free pins available on an existing 74xx00.

 

EDIT: Ha! I don't think anything went to waste on this entire board!  Okay, time to add one somewhere.

 

Edited February 10, 2022 by Panther