DIY Comms Link?

[Martin]

Dear Shaun

I'm getting behind here, in relation to the post with the picture OUT OF MEMORY ERROR (for the rest of this post referred to as ERROR)

Firstly the picture is great.

I think you are nearly there... This ERROR cropped up in discussion on our previous version of the forum before we lost it. When I did a Review and Test for Andrew on one of his USB Comms Links. In one of the trials I got the ERROR if the connection pins were not 'just so' I think they were slightly too short. Bye the way I did FRY one of his boards by cross connecting the pins (to the right I think). Do be careful with that.

Also I used to get that ERROR 'very occasionally' on my LZ64 when plugging in my 'original RS232 Comms Link' if I had other 'bootable' program packs installed... I'm not sure, others might know better but I think it is a 'boot space' memory conflict.

Getting different results on CM/XP(LA) and LZ

The Technical Reference Manual contains release notes for most of the ROM versions including the bugs and fixes.

Sincerely and in good faith
Martin

References to the Out of Memory Error
Although not exactly what you want there is reference to 'OUT OF MEMORY' error on page page 125 of the Technical Reference Manual.

The LZ Programming Manual defines 254 OUT OF MEMORY as Either the internal memory of the machine is fully occupied by programs, diary entries and data files, or the current program has used up all available memory.

The LZ Comms Link has a section OUT OF MEMORY message? - there isn't enough internal memory (4K approximately) left on your Organiser to load the Comms Link software.
 Clear some memory - e.g. delete any non-vital files or records; use the Tidy option in the Diary; or Save your files to Datapak and then erase them on A:.
 Return to the top-level menu. Press [ON/CLEAR].

If you get the same error message, clear some more memory.

[Bumblemittens]

Dear Shaun

I'm getting behind here, in relation to the post with the picture OUT OF MEMORY ERROR (for the rest of this post referred to as ERROR)

Firstly the picture is great.

I think you are nearly there... This ERROR cropped up in discussion on our previous version of the forum before we lost it. When I did a Review and Test for Andrew on one of his USB Comms Links. In one of the trials I got the ERROR if the connection pins were not 'just so' I think they were slightly too short. Bye the way I did FRY one of his boards by cross connecting the pins (to the right I think). Do be careful with that.

Also I used to get that ERROR 'very occasionally' on my LZ64 when plugging in my 'original RS232 Comms Link' if I had other 'bootable' program packs installed... I'm not sure, others might know better but I think it is a 'boot space' memory conflict.

Getting different results on CM/XP(LA) and LZ

The Technical Reference Manual contains release notes for most of the ROM versions including the bugs and fixes.

Sincerely and in good faith
Martin

References to the Out of Memory Error
Although not exactly what you want there is reference to 'OUT OF MEMORY' error on page page 125 of the Technical Reference Manual.

The LZ Programming Manual defines 254 OUT OF MEMORY as Either the internal memory of the machine is fully occupied by programs, diary entries and data files, or the current program has used up all available memory.

The LZ Comms Link has a section OUT OF MEMORY message? - there isn't enough internal memory (4K approximately) left on your Organiser to load the Comms Link software.
 Clear some memory - e.g. delete any non-vital files or records; use the Tidy option in the Diary; or Save your files to Datapak and then erase them on A:.
 Return to the top-level menu. Press [ON/CLEAR].

If you get the same error message, clear some more memory.

Thanks Martin for the pointers,

Other than messing up the data lines going to the 74ls244 I can't see any other problems, it might be a simple as Andrew mentioned that it could be an addressing issue I will check the layout again, strangely the organiser doesn't crash from the error, pressing a key goes back to the menu, more strangely removing only the EPROM causes no error at all so I'm guessing it's loading something but something is out of order, anyway thanks for your patience and help guys, kinda jumped in out of my depth lol

Edit: I've checked over and updated the schematic and attached it below, hopefully this times a winner

Shaun

[Zenerdiode]

…yeah its big and ugly…

Naah, not really. It’s not wasted on me that all of the resistors are placed with their colour bands in the same orientation. Also, with your 27C256, in another 20 mins or something - you can have another go.

[Bumblemittens]

…yeah its big and ugly…

Naah, not really. It’s not wasted on me that all of the resistors are placed with their colour bands in the same orientation. Also, with your 27C256, in another 20 mins or something - you can have another go.

I'm more comfortable with through hole for prototyping, easy to work with, all my z80 stuff is through hole, I just enjoy the design and building process

[Martin]

Shaun

I've added your schematic to those listed on the Technical Reference Manual Page

Sincerely and in good faith
Martin

[MartinP]

Bumblemittens,
Did you get any further with this? It seemed so close to working. I looked at the schematic and couldn't find any problems, so I'm guessing that any issues are with the build or the ROM image?
To bypass some ROM problems you could try it with the EPROM removed and the Comms Link ROM written to a datapak (although you'll need either another Comms Link or a datapak writer https://organiser2.com/viewtopic.php?t=56 to do that).
I like the through-hole approach and your faithful reproduction of the original. I think the big board just adds to its appeal.
Cheers,
Martin P.

[Bumblemittens]

Hey Martin,

I kinda got frustrated and put this board on the back burner, I returned to the project a few days ago and checked the schematic back to front, I burnt the comms42.opk to a datapack and put it in slot B: with the comm board plugged into the top slot and to my amazment no magic smoke, whats more when i short the TX & RX on the comm board and run the term program on the organiser i get chars looped back, so im guessing serial is all good but the problem seems to be with the on board rom image, I've tried the comms43-jumbled.bin without success so the comm board is working but not working at the same time.

Wondering if there is a way to convert comm42.opk to a bin file or intel hex so i can burn the eprom directly?

Slow progress
All the best
Shaun

[Bumblemittens]

Well folks i'm kinda at a stalemate with this thing, nothing i do will make the rom image work, though i am somewhat closer to the end goal of remote serial data collection, connecting a gps module to the board and running term results in raw gps data being shown, small win, just need to parse it into something usefull.

psion.jpg

I'm going outside and may be some time

Shaun

[amenjet]

I've just had a look at the schematic on Jaap's site and there is something odd about it (and your schematic as well, as it is a copy). A0 on the EPROM doesn't get driven by the SCLK signal. I have my doubts that this is how the actual circuit is wired up as it effectively wastes half of the space in the device. I doubt Psion would do that in their actual product. So, does your jumbled file take account of this wiring? If you look at the paralink schematic you will see that the ROM A0 on that schematic is wired to the SCLK line. That's what i would expect. Might be worth looking at that.

The rest of your circuit looks to be fine as you are getting good data, so it's not going to be anything massive that is wrong.

Andrew

[amenjet]

I've just looked back and seen that I sent the jumbled file to you. I don't think that the jumbling will be correct for your circuit as I had A0 wired to the SCLK signal. I think you need to take that jumbling and duplicate every byte, getting a file that is twice as big, then program that and see if it works.

Andrew