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Epson PX-8 Oval Display Adaptor

Crashedfiesta

Crashedfiesta

Experienced Member
Joined
Apr 16, 2022
Messages
139
Hi all, my first post.

I've got an Epson PX-8 which was a donation from one of my work colleagues. He also gave me a couple of boxes that I started to look at today. They are a UD-80 Video Display Controller and a DS-8 Device Switch. I'm focussing on the display controller for now and, after a slightly nerve shredding plug-in and switch on it didn't go "BANG" and actually is outputting something.

PXL_20220416_121529637.jpg

PXL_20220416_122852199.jpg

After my initial joy at the thing actually showing something on screen I realised I don't have the right cable to plug between the UD-80 and the PX-8. The box of stuff that came with the PX-8 had what looks like the world's supply of DIN cables but the serial 8 pin DIN to 8 pin mini DIN is not among the pile so it looks like I'll have to make up my own.

This is a real long shot as these things seem to have been exclusive to the UK but does anyone have any idea what the pinout of the serial I/O connector could be on this? Or some advice on figuring it out without blowing it up?

Thanks!

A pic of the inside (I'm a new member so hope these post correctly):

PXL_20220416_114406362.jpg
 
Thanks for the information! Your site has been a great resource and I even managed to get the games in the ROM section to work on my unit:

https://crashedfiesta.blogspot.com/2022/04/px-8-its-not-all-bad.html

I have the correct (I assume) ROM capsule for the UD-80/DS8 that has two files:

DS8DRV.COM - the main driver for the unit
WSX.COM - a loader for WordStar specifically for use with the UD-80 but needs the original Wordstar ROM installed

To be honest I'm not sure the PX-8 I have is working 100%. I have removed both the main battery and auxiliary battery which had both leaked although not too much, and I'm driving it just from the original mains adaptor (6v DC about 600ma). This means I need to do a lot of repetition of tasks when I'm trying to get the unit to work properly:

1) Boot up
2) use CONFIG to add at least 7 pages of user BIOS
3) run DS8DRV.COM

If I press Ctrl-PF1 (as suggested in the review you kindly linked to) then most times the unit hangs but sometimes nothing happens. If it's connected direct to the UD-80 with the 5 pin DIN to 8 pin mini-DIN then the screen flashes white-grey-black and the prints the entire character set almost like a startup test. But as the PX-8 is hung no key presses appear on the screen.

I tried to trace out the 8 pin serial connector on the UD-80 and, following some sleuthing with the other cables and connectors on the DS8 I now know that there are only five lines used - which explains why the review also indicated that the UD-80 could be connected to either the serial or RS-232 ports. The pins connected are:

GND - pin 2 on 8 pin UD-80 connector which is different to the PX-8 and DS-8 pin numbering
TxD - assumed pin 1 on 8 pin UD-80 connector based on pin 3 being RxD
RxD - assumed pin 3 - poking this with +5v causes the UD-80 to display a random character
DTR - not sure if this could be looped back pin 4 or 5.
DSR - not sure if this could be looped back pin 4 or 5.

I suspect I need to go back to basics and check this thing will actually print to one of the printers I was also given using the serial port. The unit did also come with a 128kb RAMDisk but this seems to stop the PX-8 from booting when it is attached. The battery has also been removed from the RAMDisk too. Any advice on batteries is also gratefully received!

More photos including some of the inside of the DS8:

DS8 Internals
DS8 Internals - there's not as much in this one although it is technically only a switch box.

PXL_20220416_115428432.jpg
The reverse of the DS8 circuit board. Old school with no solder mask.

PXL_20211213_195258349.jpg
TF15 Unit - I have no disks of the correct format. The unit is heavy enough to destroy small buildings or a toe if it's dropped...

PXL_20211213_195534000.jpg
P-40 and P-80 printers, yet to be tested..
 
Just realised it looks like I don't have the correct driver program for the UD-80. It should be called 'UD80-DRV.COM' and the one I have is for the DS8 and is called DS8DRV.COM. That could be a problem....
 
I should have read that review properly! It actually says that the driver downloads from the UD-80 itself using Filink!

Screenshot_20220419-222240.png
Just need the right serial cable! 😁
 
So, I managed to get some garbage to appear on the screen using a breakout cable to try and figure out the UD80 i/o pinout. But I've not been able to find how to trigger the unit to download the driver to the PX-8 so I'm at a dead end with this. It's really frustrating as I'm pretty sure this will work, and it would be so cool be able to show it off as well as document it a bit more for anyone else that stumbles across one of these things.

PXL_20220418_134010984_MODDED.jpg

Stuff I need:

UD80 I/O 8-pin port pinout
Instructions on how to prompt the UD80 to start the UD80-DRV.com download to PX-8. Assume in FILINK i need to 'Receive' a file with name 'UD80-DRV.COM'...

I've added this to my blog so if anyone is interested. Of course if anything else comes up I'll come back and update here too. Blog is here.

Cheers.
 
I have made some progress. I now have the correct cable configuration for the PX-8 to UD80 I/O. I have also worked out that the non-descript 'button' on the UD80 is what initiates the download of the driver. The current 'button' doesn't work very well as it reads over 50 ohms when pressed. To get around this I soldered in a rather battered but still functional key switch from an Acorn Electron. This is the result:

A20 (6) - CopyUPDATED.jpg

I nearly fell off my seat when I saw this! At the PX-8 end was this:

A20 (2) - Copy.jpg

I made a mistake and allowed the WSX.COM WordStar extension to overwrite the UD80 driver the first time (only photo I have so far - there will be more) but going through the process again and just running the driver gives me this:
A20 (10) - CopyUPDATED.jpg

The garbage at the top is caused by the 'Menu' system the PX-8 defaults to. I know I can turn it off and get it just to go straight to the drive prompt but as there are no batteries in anything, that setting just gets lost as soon as it is unplugged. Just pressing 'Esc' puts it back to a standard CP/M prompt and there you go.

Another couple of screens:
A20 (1) - CopyUPDATED.jpg

This one shows the DIR command on the PX-8 and then running FILINK. Text appears exactly as it would on the PX-8 LCD screen. Note that distortion and shadowing is most likely the display I'm using (it's a reclaimed laptop screen with a cheapo driver board). I intend to build an RGB cable for this which I hope will be compatible with SCART...

Here's the documentation I stumbled across in the original manual that the donor had supplied but that I had not looked at (because I'm an idiot)! 'Handshake In' is DTR and 'Handshake' Out is CTS which are the connections I was missing...

A1 - Copy.jpg

I shall post more pics and updates when I have time!
 
Hi Crashedfiesta,

Thanks for the images and descriptions. Here some comments on both this post and the blogspot.

On the PX-8 without batteries: according to the manual, the mains adapter is intended as a charging unit for the batteries, not for running the PX-8. We are lucky it works, but running from batteries is the intended way for a PX-8.

In the case of the HX-20, the main battery is even used as part of the voltage regulation for the logic on the board. Without batteries, the voltage for the logic can easy get outside the range for TTL (or the CMOS-equivalent).

For the TF15 disks, as this unit doesn't tries to boot from the disk like the TF-20, you could try to format an empty disk if you have the disk utilities in your system. Just the old 360k floppies for the IBM PC are ok. But even those can be hard to find tese days. Being a collector for a long time is an advantage here :-).

Just recently I found there is an emulator for disks and video here: https://www.mh-aerotools.de/hp/hx-20/
It requires a small user-bios extension (provided) on the PX-8. I haven't tested it yet.

The photo's of the DS-8 should be enough to reverse engineer the board. But I am not sure I would need such a device without a UD-80.

Greetings,
Fred Jan
 
It would be interesting to make the driver program available.

It could be useful also for other display solutions as it probably hooks into the system and simply sends a copy of the console output to the serial interface.
I guess the COM program is rather small?

Martin
 
fjkraan said:
Hi Crashedfiesta,

Thanks for the images and descriptions. Here some comments on both this post and the blogspot.

On the PX-8 without batteries: according to the manual, the mains adapter is intended as a charging unit for the batteries, not for running the PX-8. We are lucky it works, but running from batteries is the intended way for a PX-8.

In the case of the HX-20, the main battery is even used as part of the voltage regulation for the logic on the board. Without batteries, the voltage for the logic can easy get outside the range for TTL (or the CMOS-equivalent).

For the TF15 disks, as this unit doesn't tries to boot from the disk like the TF-20, you could try to format an empty disk if you have the disk utilities in your system. Just the old 360k floppies for the IBM PC are ok. But even those can be hard to find tese days. Being a collector for a long time is an advantage here :).

Just recently I found there is an emulator for disks and video here: https://www.mh-aerotools.de/hp/hx-20/
It requires a small user-bios extension (provided) on the PX-8. I haven't tested it yet.

The photo's of the DS-8 should be enough to reverse engineer the board. But I am not sure I would need such a device without a UD-80.

Greetings,
Fred Jan
Click to expand...
Hi Fred,

Thanks for your comments. :)

I have looked at how to replace the batteries but ni-cad are no longer available (EU regs) and there seems to be some doubt that NiMh can be used as a direct replacement. I had thought about a LiPo cell (with correct control board) but it's very confusing and I don't want to burn the house down... 😬 Any advice or resources on that are gratefully received!

Sadly, none of the ROMs that came with the unit have a format command. Unless there's another CP/M command I haven't stumbled across yet that will do the same thing the floppy drives will have to wait for a while. But I will have a look at the disk emulator.

If you would like dumps of the ROMs (the DS-8 also has a driver but actually on a ROM pod) for your site please let me know. I suspect there aren't too many of these UD-80s out there... And feel free to use any of the pictures on these posts or ask for others if you want to add any to your site. 😁

I have successfully built an RGB to SCART cable which gives significantly better quality then the composite output, although the picture is still a bit 'noisy' which I suspect is the buzzy power supply in back.

Thanks again!

Crashed.
 
Martin Hepperle said:
It would be interesting to make the driver program available.

It could be useful also for other display solutions as it probably hooks into the system and simply sends a copy of the console output to the serial interface.
I guess the COM program is rather small?

Martin
Click to expand...
Hi Martin,

The driver must be small as it only requires 3 pages of user BIOS to be set up to accommodate it. At 256 bytes per page that's less than 1kb. 😁

I think I could probably get the file out of the PX-8 onto a PC via FILINK or I could use TERM. I shall have a look when I am next in the shed. :)

Thanks,

Crashed.
 
Concerning the battery packs: NiCd cells are still available (even in Europe). They are still allowed for repair purposes,, but I would recommend avoiding them due to the Cd content. For this type of application with low power consumption you can use NiMH instead - charging is slightly different but as long as you don'*t overcharge NiCd and NiMH both can be used with the same old charger and behave like NiCd cells.
LiPo need a special charger and some electronics to make sure that they are not overcharged (and eventually catch fire). For this case I would not recommend them.

NiMH are not so well suited for high power applications designed for NiCd (like electric drills or similar).
NiMH have a relatively high self discharge rate, so you should recharge them every 3 months or so to keep them alive for a long time.
If you want to buy a new charger (also useful for other applications) there are very nice ones available which can be configured for NiCd, NiMH and LiPo starting at about 50€.

Martin
 
Hi Crashedfiesta,

Sorry for the late response, a short vacation interferred :-).
Yes, I am interested in ROM images. They could be useful for the MESS-like emulators, and maybe someone wants to make a UD-80 replica if a schematic might be found (I sure would like to have one).
AFAIK, there are no problems with replacing NiCd with NiMH. The PX-8 does not try to fast-charge, which could be a problem.
Greetings,
Fred Jan
 
fjkraan said:
Hi Crashedfiesta,

Sorry for the late response, a short vacation interferred :).
Yes, I am interested in ROM images. They could be useful for the MESS-like emulators, and maybe someone wants to make a UD-80 replica if a schematic might be found (I sure would like to have one).
AFAIK, there are no problems with replacing NiCd with NiMH. The PX-8 does not try to fast-charge, which could be a problem.
Greetings,
Fred Jan
Click to expand...
Hi Fred Jan,

No problem. There are two ROMs, one in the UD-80 (although it looks like I actually have three different versions of this on three EEPROMS) and one for the DS-8.

It's interesting that the UD-80 ROM I've been using is the oldest of the three and only requires 3 blocks of user BIOS to be defined, whereas the DS-8 ROM needs 23 blocks.

I'll dump all of the ROMs and drop them over via email - is the email on your site still current? And is there any format preferred, .BIN or .HEX?

Thanks,

Crashed.
 
Hi Crashedfiesta,

The image of the DS-8 above doesn't show an EPROM, but there might have been more PCB's inside. Still trying to get the whole picture here :-).
Yes, the email is still current. HEX has checksums, but BIN is ok, as long as you don't proces it as text files.
Greetings,
Fred Jan
 
fjkraan said:
Hi Crashedfiesta,

The image of the DS-8 above doesn't show an EPROM, but there might have been more PCB's inside. Still trying to get the whole picture here :).
Yes, the email is still current. HEX has checksums, but BIN is ok, as long as you don't proces it as text files.
Greetings,
Fred Jan
Click to expand...
Just sent you an email. Let me know if the .BIN format gives you any trouble - I used a Dataman S4 to dump them (another donation from my work colleague).

Thanks,
Crashed.
 
Hi Crashed,

The zip is added to the PX-8 page at https://electrickery.nl/comp/px8/roms/. I'll hope to find time to study the ROMs and your images on vcfed.org to find out more om the DS-8. It should be doable to get a schema for this. The UD-80 might be more complex, but with some help from EF9345P / EF6803P it might be possible to create something compatible.

Thank you & greetings,
Fred Jan
 
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