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   Can I make a Comms link myself?
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   Author  Topic: Can I make a Comms link myself?  (Read 4869 times)
barfieldm
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Can I make a Comms link myself?
« on: Feb 23rd, 2004, 11:03am »
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It really is not possible to make a comms lead that would work without rewriting the comm software- i have dismantled one and attempted to reverse engineer it, but unfortunatley there is a custom IC inside which prevents this.
 
martin B
« Last Edit: Sep 13th, 2004, 7:30pm by Boris »
Maark
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Re: Can I make a Comms link myself?
« Reply #1 on: Aug 9th, 2004, 12:40pm »
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I'm a new user of LZ, unfortunetly lacking of the comms link interface. As an electronic hobbyst (and not only hobbyst I'm thinking about building CommsLink by myself (at it is hardly available as I can see )
You said there is a custom chip inside the interface - are you sure it is custom indeed (this may be just an eprom)?
I've found on the ftp here the software to download the pack contents to the PC with a note these can also be contents of the CommsLink interface eprom.
If you could provide some more info on the construction of the interface (e.g photos of the printed board inside and the chip) we could try to reverse-engineer it I think...
After reading the description of the CommsLinks it seems it is separable into two distinct parts - serial interface and the eprom with Psion system extension. In the worst case one can try to write own serial link routines in assembler and develop the the (custom) serial interface part only...
Trygve
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Re: Can I make a Comms link myself?
« Reply #2 on: Aug 11th, 2004, 9:22am »
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Yes, the comms link consists of two parts:
 
The ROMPak - which is a 54256 PROM (at least mine uses that. Only 4KB seems to be in use) and two 4024 counters for addressing it.
 
The Serial interface which is based on a 74HC244 buffer and a MAX232CWE line drivers to convert TTL levels to RS232 standard levels.
 
Incredibly enough, it doesn't use any parallell-to-serial type chips so the ORG II must 'bit-bang' the serial data itself. (Much more processor intensive, and also limits the max speed that can be achieved)
 
On the serial interface, in addition to RX/TX it only uses two other pins. (Can't remember which ones)
 
I'm looking at completely mapping the circuits, but can't say for certain when I'll get the time to do it.
 
One thing you should be aware of if you try to read off the PROM, is that pins are NOT used in the 'recommended' fashion.
Several of the DATA and ADDRESS pins are used out of order.
 
What program were you going to use to read the PROM with?
(I need it myself...)
thesourcerer
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Re: Can I make a Comms link myself?
« Reply #3 on: Aug 11th, 2004, 2:32pm »
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Thinking of the time, effort and difficulty of making a Comms Link....is it worth it? P.S. I am no longer stocking second hand Comms Links due to the arival of the new stock!
« Last Edit: Sep 1st, 2007, 11:30am by thesourcerer »
Maark
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Re: Can I make a Comms link myself?
« Reply #4 on: Aug 13th, 2004, 2:52pm »
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on Aug 11th, 2004, 9:22am, Trygve wrote:
[...]
The ROMPak - which is a 54256 PROM (at least mine uses that. Only 4KB seems to be in use) and two 4024 counters for addressing it.
I think this part should be easy to bulid... I've seen a  schematic od Datapack - something close you have described - with cmos counter and the memory chip.
 
The Serial interface which is based on a 74HC244 buffer and a MAX232CWE line drivers to convert TTL levels to  RS232 standard levels.
Seems to be trivial to build as well
 
Incredibly enough, it doesn't use any parallell-to-serial type chips so the ORG II must 'bit-bang' the serial data itself.
Interesting approach... but when OrgII was constructed UART chips must had been expensive I presume...
 
On the serial interface, in addition to RX/TX it only uses two other pins. (Can't remember which ones)
That all puts a new light on the Comms Link construction - I did not have it in my hands yet... or even seen a photo of a dismantled one...
 
I'm looking at completely mapping the circuits, but can't say for certain when I'll get the time to do it.
I think more people working on it less time it takes... (of course if the work is divided)
I could try to work-out the details, but without physical access to the CommsLink it may be not easy task... but we can try - e.g. If you have a digital camera and make a close-up pictures of the printed board.... or even put the printed board it on the scanner...
Next step would be to get the contents of the ROM out...
 
Several of the DATA and ADDRESS pins are used out of order.
 
What program were you going to use to read the PROM > with? (I need it myself...)
Once the data is read in the same way it has been written, the order of address and data lines does not matter... I see it as if we'll read the ROM with the SendPack program and transmit it to PC, we can use it later in whatever the line configuration of our module is...
The program I found is here:
http://archive.psion2.org/org2/files/sendpack.zip
 
I think it may be useful...
Of course if you could read CommsLink ROM for me I would be very grateful...
 
Best regards,
 
Marek
« Last Edit: Aug 13th, 2004, 3:55pm by Maark »
Maark
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Re: Can I make a Comms link myself?
« Reply #5 on: Aug 13th, 2004, 10:43pm »
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on Aug 11th, 2004, 2:32pm, thesourcerer wrote:
Thinking of the time, effort and difficulty of making a Comms Link....is it worth it?
It will take time, surely, but considering low complexity (as ccordingly to the Trygve's description) and fun of building it with own hands I think it is worth doing.
 
I have plenty available, despite their apparent scarcity (I've been "stockpiling" for years!), but I'm reluctant to drop the price (£50 for 4 line, £45 for 2 line).
And that is another reason - price... considering number availability of components required and even a time to build the module, it is not worth spending £45 pounds...  
 
I appreciate that it is an intellectual challenge, but is it justified?
I think it is
Trygve
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Re: Can I make a Comms link myself?
« Reply #6 on: Aug 17th, 2004, 12:33pm »
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on Aug 13th, 2004, 2:52pm, Maark wrote:

I think this part should be easy to bulid... I've seen a  schematic od Datapack - something close you have described - with cmos counter and the memory chip.

 
Yes, it's quite similar to normal DataPaks, except that this is of course a ROMPak.
 

Seems to be trivial to build as well

You'd think so, but...
If you want it compact, you need to use SMT.
There's a lot of SMT Resistors and stuff there, too...
 

Interesting approach... but when OrgII was constructed UART chips must had been expensive I presume...

Not that expensive.
Besides, the CPU in the OrgII have a built-in UART.
 

If you have a digital camera and make a close-up pictures of the printed board.... or even put the printed board it on the scanner...

Not a good idea.
his is a Surface Mount system with traces going under the ICs...
 
What I'm doing is using a multimeter with buzzer and holding one probe against a pin, then testing all ther pins to see where it's connected...
 

Once the data is read in the same way it has been written, the order of address and data lines does not matter... I see it as if we'll read the ROM with the SendPack program and transmit it to PC, we can use it later in whatever the line configuration of our module is...

 
I'll try the sendpack program later...
(My laptop is on the blink at the moment. )
 
Richard
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Re: Can I make a Comms link myself?
« Reply #7 on: Aug 17th, 2004, 11:40pm »
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I thought about attempting an internal bit banging method earlier this year as I just found two XP/LA's in my garage...
Unfortunately my only assembler experience is with PIC16F84 so the number of instructions for the Hitachi processor completely overwhealms me...
« Last Edit: Aug 17th, 2004, 11:44pm by Richard »
Maark
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Re: Can I make a Comms link myself?
« Reply #8 on: Aug 21st, 2004, 10:16pm »
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on Aug 17th, 2004, 12:33pm, Trygve wrote:

 
Yes, it's quite similar to normal DataPaks, except that this is of course a ROMPak.
I was thinking about another apporach - quite simple I think - building something like an eprom simulator - DataPack. PC would be able to modify contents of the datapack (using paralell or serial connection (e.g. with use of a microcontroller))...  
 
If you want it compact, you need to use SMT.
There's a lot of SMT Resistors and stuff there, too...
So we have to have a schematic and rethink it... I can presume resistors are mainly used in a level converter for the RS232 standard... or a pull-up? [/quote]
 
Not that expensive.
I know, bud developing such construction needs cost considerations... you remember ZX-Spectrum - it was without any peripherial connection like serial or parallel port to cut the cost...
 
Besides, the CPU in the OrgII have a built-in UART.
A... you're right I don't know OrgII cpu very well...  
 
Not a good idea.
his is a Surface Mount system with traces going under the ICs...
What I'm doing is using a multimeter with buzzer and  
holding one probe against a pin, then testing all ther  
pins to see where it's connected...

I know this is a realy a hard job...  I'm still wondering what do all these resistors do in a circuit...
 
I'll try the sendpack program later...
> (My laptop is on the blink at the moment. )


Once you have it, as a 1st stage I can try to produce the  eprom that works as the ROMPack with the CommsLink ROM... and then we can work-out the rest
 
Regards,
 
Marek
 
Trygve
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Re: Can I make a Comms link myself?
« Reply #9 on: Aug 23rd, 2004, 8:28am »
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The resistors are mainly pull-up/pull-down's.
The MAX232CWE does the level conversion from TTL to +/-12V and back.
Any MAX232 or similar chip can be used as long as it contains at least 2+2 converters and runs off a single +5V supply.
 
Maark
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Re: Can I make a Comms link myself?
« Reply #10 on: Aug 26th, 2004, 8:46pm »
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on Aug 23rd, 2004, 8:28am, Trygve wrote:
The resistors are mainly pull-up/pull-down's.
The MAX232CWE does the level conversion from TTL to +/-12V and back.
Any MAX232 or similar chip can be used as long as it contains at least 2+2 converters and runs off a single +5V supply.
 

 
First I thought they did not use MAX232 even....  
Have you tried sendpack program?
Presumably I'll be able to get the Rampack for Psion - do you think I can use as a place to store and run CommsLink rom for development? (ultimately we'll program eprom's of course).
 
Trygve
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Re: Can I make a Comms link myself?
« Reply #11 on: Aug 27th, 2004, 9:10am »
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I got my laptop back yesterday, so have only begun to reinstall all my programs, but I expect to get cracking with the SendPack program this weekend.
I'll also try to complete the Circuit-diagram then.
 
Whether or not you can use a RAMPak for development I don't know.
Trygve
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Re: Can I make a Comms link myself?
« Reply #12 on: Sep 10th, 2004, 8:37am »
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The Pack image is now uploaded to the contributions forum.
 
It seems I goofed when mapping the circuits(probably a bad probe lead), so the ROM is a whopping 32KB...
(It uses all outputs of both 4024 counters, no segmenting...)
 
A preliminary Schematic will be uploaded this weekend.
« Last Edit: Sep 13th, 2004, 8:03pm by Boris »
Maark
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Re: Can I make a Comms link myself?
« Reply #13 on: Sep 10th, 2004, 5:11pm »
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on Sep 10th, 2004, 8:37am, Trygve wrote:
The Pack image is now uploaded to the contributions forum.
 
It seems I goofed when mapping the circuits(probably a bad probe lead), so the ROM is a whopping 32KB...
(It uses all outputs of both 4024 counters, no segmenting...)
 
A preliminary Schematic will be uploaded this weekend.

That's a great work... i'll take it and try to upload to the RAMPACK somehow (I will try to handle the rampack from the PC) and see if it will boot on Psion. I presume it should and the CommsLink menu should appear... I hope the addressing of the RAMpack (Tech. Ref. says it is "paged datapack" but not "page counted", I wonder what is a difference between those two modes) won't be a problem...
 
 
 
Trygve
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Re: Can I make a Comms link myself?
« Reply #14 on: Sep 11th, 2004, 3:58pm »
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I forgot to mention 'no pageing'...
 
One pin from the Top slot goes to the A0 pin on the ROM and to the pulse input of one of the 4024 counters.
The highest output (V7) of the first 4024 is connected to the Pulse input of the second 4024.
Boris
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Re: Can I make a Comms link myself?
« Reply #15 on: Sep 13th, 2004, 8:32pm »
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on Aug 11th, 2004, 9:22am, Trygve wrote:

On the serial interface, in addition to RX/TX it only uses two other pins. (Can't remember which ones)

 
The Commslink supports CTS/RTS handshaking.
 
DSR is linked to DTR, and to AC_B (topslot - active high).
 
If the organiser is in OFF state, pulling AC_B low is exactly the same as pressing ON, otherwise the signal is ignored.
« Last Edit: Sep 13th, 2004, 8:37pm by Boris »

Triholerahduliäöhh gugguh !! (tyrolean joy jodler)
Rough translation: There's a new build of Psi2Win!!
Email: boris[at]psion2[dot]org
thesourcerer
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Re: Can I make a Comms link myself?
« Reply #16 on: Sep 1st, 2007, 11:14am »
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It has finally been done!!! I can supply the new Comms Links at 60GBP. The grey plastic topslot interface cover has not yet been produced, but ones from the power supply interfaces are perfect (the type with the LED in it). I can supply complete ones (i.e. with the cover) for 65GBP + postage. They now have the more appropriate 9 pin female connector, rather than the old 25 pin. These are high quality professionally produced items (4-line display of course). I do know it took months to develop, and cost a small fortune, but I think it now ends this topic! Long live the Psion II.
Boris
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Re: Can I make a Comms link myself?
« Reply #17 on: Sep 4th, 2007, 10:20pm »
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OK, it has been done. But this is not the answer to
     "Can I make a Comms link myself?"
The new commslinks are just exact replicas of the old commslink. This is possible, it has been possible for all these years, but it requires professonal assistance and at least production numbers above 100 to be of any sense.  
 
The answer to the question: can the average home user produce a device that replaces the original commslink is still NO!
 
Although there may be a way: SzTaMatti showed how to send data without using the commslink software.  
BTW. This works best at 19200 baud (which is double speed!!!)
 
[edit: fixed the link and removed the complaints about the bad link]
« Last Edit: Sep 11th, 2007, 10:15pm by Boris »

Triholerahduliäöhh gugguh !! (tyrolean joy jodler)
Rough translation: There's a new build of Psi2Win!!
Email: boris[at]psion2[dot]org
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