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1088XEL Atari ITX Motherboard DIY Builders Thread

1088XEL JOY2PIC-STIK XEL-CF-][ UAV Sophia U1MB

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#926 mytek ONLINE  

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Posted Fri Jun 15, 2018 2:13 PM

Ah didn't know about that one....current is not an issue here....it's close to 0. That's why it can be done with a simple set-up like I mentioned...a cap being charged by the sync pulses :) I was quite impressed by the cleverness of this simple trick back then....wish I could find the schematic back....argh....
 
Yeah, trouble is that 
 
1) the cable coolnovilties sells probably doesn't carry anything to pin 8 on the SCART connector
2) no idea if an added signal like that would screw up ST compatibility with that cable ;) (if it IS ST compatible that is :))
3) some people might actually like the screwed 16:9 look....  :-o  :_(


Answers...
 
Item 1: Nothing is wired to pin 8, in fact every wire that is available is presently in use.
 
Item 2: This cable is 1088XEL specific and will not work properly on an ST.
 
 

The idea with the diode and cap (IIRC) can be mounted inside the SCART connector which is nice....no need for an extra wire (hack).

 
I like that idea  :thumbsup:  :) . Since the Control signal is 5 VDC and a ground is available, it would be relatively easy. There's enough room in the SCART connector housing for something like a 555 and the diode/capacitor charge pump.
 
VoltageDoubler.gif



#927 Level42 OFFLINE  

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Posted Sat Jun 16, 2018 5:13 AM

Way too complicated. 

 

I think a simple diode and cap on the sync signal could do the trick, however, I'm not sure if this could reach +9V.....

 

The other option is a dedicated voltage doubler chip....it is 2018 after all ;)

 

Here's a tiny one that will fit EASILY, even with the 2 required caps.

 

https://datasheets.m...682-MAX1683.pdf

 

It would be even better if no external caps were required....maybe there are other voltage doubler chips that feature that...



#928 Level42 OFFLINE  

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Posted Sat Jun 16, 2018 7:23 AM

Here's some others, they all seem to require 2 caps:

 

https://www.onsemi.c...al/CAT660-D.PDF

 

https://www.onsemi.c...al/MAX828-D.PDF



#929 mytek ONLINE  

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Posted Sat Jun 16, 2018 8:59 AM

I looked up the spec for the voltage range required on pin 8 in order to switch into 4:3 mode. It's 9.5-12vdc. The minimum requirement is slightly more than what a diode/capacitor voltage doubler circuit would produce from a 5vdc input. However very much in range for a tripler circuit of a similar nature, an example of which is used in the JOY2PIC. And your idea of using CSYNC as the oscillator to drive it seems feasable, although the duty cycle isn't ideal, but should be good enough for our purposes. When I get a chance I'll have to breadboard a circuit and give it a go :).

#930 mytek ONLINE  

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Posted Mon Jun 18, 2018 11:44 AM

End-Of-Life Notice for 1088XEL Color Trim Pot

500K Pot end-of-life.png

Bourns 3319P-1-504

Trimmer Resistor - Through Hole 9MM RND 500K OHMS 25% 0.2WATTS

 

Presently available from:

 

Digikey P/N 3319P-1-504-ND

Mouser P/N 652-3319P-1-504

 

I clicked on the suggested substitute and it did not appear to be in the correct orientation as the original part. So here are the physical specs that would need to be matched up with.

 

3319P-1-504.png

 

 

 

 



#931 orpheuswaking OFFLINE  

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Posted Tue Jun 19, 2018 9:19 AM

Time to buy them out :D



#932 Level42 OFFLINE  

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Posted Sun Jul 1, 2018 3:35 PM

I looked up the spec for the voltage range required on pin 8 in order to switch into 4:3 mode. It's 9.5-12vdc. The minimum requirement is slightly more than what a diode/capacitor voltage doubler circuit would produce from a 5vdc input. However very much in range for a tripler circuit of a similar nature, an example of which is used in the JOY2PIC. And your idea of using CSYNC as the oscillator to drive it seems feasable, although the duty cycle isn't ideal, but should be good enough for our purposes. When I get a chance I'll have to breadboard a circuit and give it a go :).


Curious if you already found some time for this ?

Edited by Level42, Sun Jul 1, 2018 3:35 PM.


#933 mytek ONLINE  

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Posted Mon Jul 2, 2018 1:33 AM

Curious if you already found some time for this ?


Sad to say no I haven't. Lately I'm going in an entirely different direction and unfortunately don't have time for my Atari stuff. That'll change, but not for awhile I'm afraid.

#934 Level42 OFFLINE  

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Posted Mon Jul 2, 2018 2:19 AM

Oops....that doesnt sound good....Ill have a try at it Micheal..... whatever it is: all the best !

Edited by Level42, Mon Jul 2, 2018 2:20 AM.


#935 DrVenkman OFFLINE  

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Posted Sun Jul 15, 2018 12:38 PM

So I found the first real compatibilty issue with my 1088XEL this week ...

 

I built a really cool little Arduino-powered disk/tape emulation device called an SDrive-MAX, as described here:

 

http://atariage.com/...ax-atx-support/

 

and in the original project page (German, but Google Translate will give you what you need)

 

http://www.kbrnet.de...-max/index.html

 

I built my device with the recommended 1N4148 diode (cathode side to the Arduino TxD pin) in order to allow use with other SIO devices. Unfortunately, with the diode installed, the Arduino can't seem to communicate back to the 1088XEL. I see SIO requests on the display but no data from the SDrive-MAX is making it back to the XEL. When I removed the diode, the thing works like gangbusters, even accelerated loading using Jon's PBI driver and HSIO. But of course, once connected without the diode, it prevents use of either the SIO2PC interface on the Sparkfun board or real floppies. 

 

I measured the diode's forward bias at 0.6 volts, reverse bias is 0 as expected. Just to make sure it wasn't an issue with the diodes I have, I bought more from another vendor. They arrived today, measured identical to the first set of diodes and using one of them, of course the device still doesn't work.

 

So I did what I probably should've done last week: I dug out my 1200XL (modded to add +5V back to the SIO pin). The device, diode installed, works great. Booted up DOS, then booted up MULE for good measure. No trouble at all.

 

The question then, obviously, is what's different about the 1088XEL SIO interface compared to an almost-stock 1200XL's to make it not function with this device and a diode installed? Is it because of the internal Sparkfun board? I'm curious to hear anyone's thoughts.



#936 LarryL OFFLINE  

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Posted Sun Jul 15, 2018 12:54 PM

I am not sure if it is really an issue of the 1088XEL.
I am operating the XEL with the SDrive-MAX since some weeks already - with diode, powered via the SIO from the 1088XEL, without any problems.

The SDrive-MAX is the only SIO-Device I am operating (except the inbuilt sparkfun of course) - although I did not try to operate them at the same time

Regards
Michael


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#937 _The Doctor__ OFFLINE  

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Posted Sun Jul 15, 2018 1:14 PM

make sure all devices are in 5v modes..... ftdi spark fun red board etc..


Edited by _The Doctor__, Sun Jul 15, 2018 1:20 PM.


#938 LarryL OFFLINE  

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Posted Sun Jul 15, 2018 1:18 PM

Sure??.
We had this discussion some time ago - switch on the FTDI needs to be on the right side, I.e. 3.3V, not 5V



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#939 _The Doctor__ OFFLINE  

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Posted Sun Jul 15, 2018 1:22 PM

that was my suspicion back then, it turned out to be true... and from time to time it happens again as people mess around inside the XEL disturbing the switch or miss that step in the install. Always good to double check ;)


Edited by _The Doctor__, Sun Jul 15, 2018 1:23 PM.


#940 DrVenkman OFFLINE  

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Posted Sun Jul 15, 2018 2:13 PM

make sure all devices are in 5v modes..... ftdi spark fun red board etc..

 

 

Sure??.
We had this discussion some time ago - switch on the FTDI needs to be on the right side, I.e. 3.3V, not 5V

 

 

 

Okay, guys? That's not the issue. As-is, the 1088XEL can communicate with both the SIO2PC and floppies, independently or simultaneously.

 

The issue is the use of the SDrive-MAX with the recommended 1N4148 diode in-line with the XEL prevents use of either of those other two options; it takes over the SIO bus and nothing else can talk to the XEL.

 

When I install the recommended diode, the SDrive-MAX no longer works with the XEL.

 

However, with the diode installed, the SDrive-MAX still works great with my 1200XL. 



#941 mytek ONLINE  

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Posted Sun Jul 15, 2018 2:47 PM

Since the SDrive-MAX works well without the diode, other than the fact it takes over the bus, I would suspect that this should be a relatively simple thing to fix..

 

It almost seems like the 1N4148 might be creating too much of a voltage drop (0.7V) in the case of the XEL with it's SparkFun FTDI board resulting in the signal not being recognized because it's too low of a voltage swing. I would try a Schottky diode which has a far smaller voltage drop (typically >0.2V).

 

Mouser P/N: 78-BAT85S-TAP is a small current device with a standard D0-35 case style (same as a 1N4148) that should work fine as a replacement.

 

Certainly worth a try.



#942 _The Doctor__ OFFLINE  

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Posted Sun Jul 15, 2018 2:48 PM

still sounds like a level issue so go with a diode with less of a voltage drop as previously mentioned in the other thread earlier (possibly yesterday or the day before) , they usually are faster acting as well..

 

 

edit....  lol  Thanks Michael, that's 4 votes for the diode now, you posted at the same time :)

 

further edit...  maybe this should be added to the manual, when using homebrew sio devices blah blah  diodes of this schottky type or this trigger type with example numbers is highly recommended....

 

further further edit, all the web sites with sio2 this or that should be contacted to make the note or change as well, I see this as a re-occurring issue through out time not only with 1088XEL but other projects now and going forward in time....


Edited by _The Doctor__, Sun Jul 15, 2018 3:09 PM.


#943 DrVenkman OFFLINE  

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Posted Sun Jul 15, 2018 3:35 PM

Since the SDrive-MAX works well without the diode, other than the fact it takes over the bus, I would suspect that this should be a relatively simple thing to fix..

 

It almost seems like the 1N4148 might be creating too much of a voltage drop (0.7V) in the case of the XEL with it's SparkFun FTDI board resulting in the signal not being recognized because it's too low of a voltage swing. I would try a Schottky diode which has a far smaller voltage drop (typically >0.2V).

 

Mouser P/N: 78-BAT85S-TAP is a small current device with a standard D0-35 case style (same as a 1N4148) that should work fine as a replacement.

 

Certainly worth a try.

 

Thanks, Michael. I will order some of those and give it a try. :)

 

In the meantime, I did another experiment - I took a brand new Arduino UNO clone board just like the first one, built out a new cable assembly, then soldered it to the Arduino *WITH* the diode. The only thing I reused is the touch screen module. I then tried it with the 1088XEL. Still no go. I do get boot errors from the computer, so it's TRYING to communicate, but nothing is getting through.

 

I plugged it into my 1200XL with a floppy drive connected as D2:. Just like before, the 1200XL powered right up. I loaded DOS and was able to access the floppy as D2:, so … the 1200XL still works but, the XEL does not.

 

I wonder if I removed the +5V line and powered the SDrive-MAX via a wall-wart if it would make any difference? I tried yesterday using a 9V battery adapter but that didn't work either.



#944 DrVenkman OFFLINE  

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Posted Sun Jul 15, 2018 6:35 PM

So as it happens, I was digging around the parts bin and while I didn't find the type of Schottky diode Michael suggested, I did find that I had 10 - 15 small 1N5189 Schottky diodes. Never content to wait if I don't have to, I rewired the SDrive-Max to use that one rather than the 1N4818 specified. 

Whaddaya know? It works just as advertised now, mixing real and virtual drives it's supposed to. I booted up a game a M.U.L.E. at super-speeds to listen to that happy music and celebrate. :)

 

Thanks for getting me pointed in the correct direction, folks!



#945 mytek ONLINE  

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Posted Mon Jul 16, 2018 1:14 AM

Most all Schottky diodes have a similar voltage drop, so any one of them should work. Glad to hear that solved your problem.

 

Edit: So apparently the BOB-12731 FTDI Break-Out Board being used for the SIO2PC-USB on the 1088XEL exerts a bit more pull-up then the normal 4.7K resistor on the SIO Data-In, thus requiring a bit more pull-down by the diode. I can't see any on-board pull-up resistors on the BOB board, so this must be something inherent in the FTDI chip itself (might be associated with internal level shifting).



#946 DrVenkman OFFLINE  

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Posted Mon Jul 16, 2018 4:42 PM

Most all Schottky diodes have a similar voltage drop, so any one of them should work. Glad to hear that solved your problem.
 
Edit: So apparently the BOB-12731 FTDI Break-Out Board being used for the SIO2PC-USB on the 1088XEL exerts a bit more pull-up then the normal 4.7K resistor on the SIO Data-In, thus requiring a bit more pull-down by the diode. I can't see any on-board pull-up resistors on the BOB board, so this must be something inherent in the FTDI chip itself (might be associated with internal level shifting).


Thank you again so much for pointing me in the right direction Michael! Tonight I am running tests on my 1088XEL. Booting SDX from the internal U1MB, I have confirmed that my SDrive-MAX now works perfectly.

At the moment, I have D1: mounted on the SDrive-MAX, D2: is a stock 1050 drive, D3: and D4: are images mounted to slots in RespeQt connected via the Sparkfun board, and D5: through D9: plus DJ: through DL: drives are all mounted in the CF card in my XEL-CF interface. And they all work at the same time just fine.

Atari storage nirvana!!! :D

#947 _The Doctor__ OFFLINE  

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Posted Mon Jul 16, 2018 5:18 PM

Dr. Venkman, did the other guy say it was a star card?  Dr. V ....  Star card in hand.... incorrect  :)     zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzttttt cackle zzzzzap!

:)



#948 Lavalamp OFFLINE  

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Posted Sat Aug 4, 2018 5:49 AM

Im not able to get my 1088XEL running, :( is someone able to to have a look at it? Happy to send it to you.



#949 MacRorie OFFLINE  

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Posted Sat Aug 4, 2018 6:38 AM

Im not able to get my 1088XEL running, :( is someone able to to have a look at it? Happy to send it to you.

 

I would be more than happy to take look at it.  PM me with what it is doing/not doing.







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