Sinclair ZX80 / ZX81 / Z88 Forums

Hi,

I bought my ZXpand+ in november/december 2017. Up to recently, it was working very well.

But it started behaving strangely the past few days. The problem is the following:

When I do "CAT". The listing of the SD card is corrupted. The problem started with just a few catalog entries that were missing their first character. Like REDANT.P would read "EDANT.P". It was not always the same file that was missing characters. It would change just by typing CAT again. The day after, catalog entries stated missing more than one characters, with many more corrupted names.

Right now, when I type CAT, there are only a few files that are listed, some with corrupted names. Again the number of files listed will vary. Also the error report at the bottom of the screen is funny i.e. it consist of some graphic character followed by /0.

That being said, I CAN STILL load any/all programs on the card if I use the real name. And so far, all programs loaded are NOT corrupted and will run without problems. To me, this means that the files and directory structure on the card are fine. As expected, they are not corrupted when I check them on a PC.

An additional information that might be related or not: when I received the ZXpand+, the pin#1 of the chip labelled PIC18F4525 was not seated completely inside the socket, instead it was bent with a kink but the tip would nevertheless enter the socket hole but not by much. As the interface was running correctly I decide not to fix the problem thinking that the pin must have a good contact anyway. (I did not want to remove the chip and break the pin somehow when trying to straighten it)

I am really not sure that pin has anything to do with the problem I have, but I am sure someone here will know. Otherwise, is this a known problem ? What can I do in order to have non corrupted catalog listing again?

I can post pictures of the screen or the board if needed.

Thank you.

Francois Lanciault

May or may not be related but when I first started using SD cards with ZXpand I had problems so I moved files on windows and the reformatted to 4MGB FAT16. More than enough space right? And then copied them back onto SD.

Then the problems dissappeared. Maybe a file disk fragmentation problem.

Its certainly worth trying another card if possible.

I use a 2gig card with about a gig of MIDI and other music files on it no problem so would initially suspect a broken card rather than a card size/format type problem.

Also if using the "ZXPAND COMMANDER" file app' there is a limit on the amount of files that can be displayed in the root folder (256 I think)though that's not a likely cause in this case I would have thought.

You mention in your post a bent pin. I would certainly straighten that out as the contact could be intermittent, with the caveat of if you are unsure of how to safely do this yourself without causing damage then perhaps someone you know with more knowledge/confidence etc could be entrusted to do it for you.


Pictures would be great also as The ZXpand creator Sir Morris will see this thread I'm sure and a visual aid may be of help to him.

Please let us know how you get on.

Hi sorry, I just spotted this.

Pin 1 is not used in normal operation - it is normally RESET but it is disabled once the PIC is programmed. I am slightly ashamed that a bent pin wasn't noticed but that is probably because it has no use.

How are things now? Is the problem still happening? It's most odd, CAT fails but LOAD works... It means there's nothing wrong with the SD card transfer protocol as the same mechanism is used for CAT and LOAD. It could be a slight corruption of the firmware in the PIC chip. I would suggest re-flashing it. Instructions are HERE and the file needed for flashing is HERE.

If it's not the PIC then it might be a corruption of the EEPROM's firmware but this is less likely. Do you have an EPROM programmer?

Please keep me informed of progress, or otherwise.

C

Hi,

Thank you for your response.

I check the zxpand+ again yesterday, but now nothing works anymore.

When I apply power to the computer, the two LED flash in sequence as usual but nothing appears on screen i.e. no copyright message and no cursor. Sometime, there will be some strange patterns on the screen.

Thinking it might be a zx81 problem, I unplugged power, and tried the zx81 alone. There was no problem. I tried it with the 16k ram pack and my 32k memotech pack and everything is fine. I re-tried the zxpand+ but same problem.

Now this problem appended once before Christmas. Same thing, the zx-81 with zxpand would not work but the zx-81 alone would. The next day however the zxpand+ was working again and, as I said, as been working flawlessly until a few days ago.

I will try again tonight. I will also clean the zx81 edge, who knows! If the problem is still there, I will try re-flashing the PIC. Does pin#1 needs to be seated for a re-flash ?

Best regards!

P.S. Your interface is really wonderful. I got back at programming the zx-81 and the workflow is so much easier. What I am most interested into is the serial port. I have not tested it yet however. BTW, I see in the doc how to send streams of bytes thru the serial port but I have not seen anything about receiving bytes. Is there a call for that (machine code or otherwise). Thank you for your help.

Definitely worthwhile cleaning the edge-connector

Mark

+1 for cleaning edge connector. And wiggling the ZXpand in-place with the power off.

There is a slim possibility that the CPLD has become corrupted. Do a CPLD re-flash too using the second part of the instructions posted earlier and THIS file.

The process takes 3-4 minutes, and it might look like nothing is happening for a while. The Yellow LED will light and there will be intermittent flashes of green, with a flurry of activity at the end.

If this all fails we may have to discuss a replacement via PM.

C

Hi again,

I cleaned the zx-81 edge connector and, when I say clean, I mean I removed the zx81 PCB, I rubbed the edge connector with a 1000 grit sand paper until it shinned, cleaned the connector and the surrounding with IPA and, to my pleasant surprise, the ZXpand+ is now fully working.

The CAT function works normally, at least so far.

Also, when I first received the board, I downloaded many programs to test the capacity of the zxpand+. All of then worked except one: "Intergalactic Space Rescue" which would crash the computer. At the time I assumed my download was corrupted or I downloaded the wrong HRG protocol. But now it works. Go figure.

Anyway it think the dirty connector clearly explain the blank screen issue. For me, it is less clear on why a dirty connector would create the CAT listing problem I was having... If that problem pops-up again I will let you know.

I can now return to my development activity with, next on the program, testing the serial port. Any answers on my question on how to receive serial data from the zx81 ?

Francois

Please start a new topic in Development to discuss the serial transfer. That way the information will be easier to find for others wanting the same thing. Also I'm not sure what you mean - 'Receiving data from the zx81' implies that the zeddy will be sending to some other device - is that the case? Or do you want the zeddy to receive? In the first case there is an explanation in the manual, but receiving data isn't something that is well documented. I will be happy to fill out the documentation with guidance from a real-world use case!