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HP Forum Archive 13

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HP-IL story continues...
Message #1 Posted by Pavel Korensky on 11 Nov 2003, 9:05 p.m.

Couple of days ago, I mentioned here that I got an old rusty HP82161A unit.

I disassembled it, carefully washed the PCBs in warm soap water and I let them dry.

When everything was dry, I desoldered the HP-IL parts (IC, transformer, inductor, capacitors, resistors etc.) and I put them on a prototyping board. I attached this board to my ATMega103 development board, wrote a piece of software and BINGO - I have a nice HP-IL analyzer which is attached to my PC notebook via RS-232 connection. Software is not yet completely finished (I need to implement all HP-IL message tables), but it seems that both IC and transformer are working. The transformer seems a bit dirty, but it works.

During this week, I should receive the 64MB MMC card. When I will have it, I will start to implement the mass storage which will mimic the HP82161A. In the first design, it will be necessary to use the RS-232 port for "tape exchange". There would be 500 "tapes" available on 64MB card, each tape will have name and the LIF files will be stored inside normal DOS/FAT files. This way, it will be possible to write some PC software for LIF files organisation (something like "select those HP-41 files and copy them to file TAPE01 on MMC).

Re: HP-IL story continues...
Message #2 Posted by Christoph Klug on 12 Nov 2003, 5:29 a.m.,
in response to message #1 by Pavel Korensky

Dear Pavel,

please go on with your work about Hp-IL Mass storage Unit. Also add an battery power supply for portabel applications. Your system would be a nice extension for I/O-Board and IL2000 system (hardware interfacing / measurement / data logging).

If you need, I can make available some IL-Transformers and IL-Chips for your project :-)

Best wishes from Germany - Christoph Klug

Re: HP-IL story continues...
Message #3 Posted by Pavel Korensky on 12 Nov 2003, 4:15 p.m.,
in response to message #2 by Christoph Klug

Yes, there will be the battery power supply.

I do not need the IL parts. At least not until I will fry the chip which I desoldered from HP82161A. :-)

But, there is another problem. I am planning to release all schematics, sources etc. as a Open Hardware. But the IL chips and transformers are hard to find and it is strange to start the design description with something like "1. Find a broken HP-IL unit and desolder the IL chip and transformer from it...."

I can imagine, that I can duplicate the IL chip (with minor modifications - only digital inputs) in form of CPLD. But I am a terrible analog desinger and I can't figure out, how to design the replacement for a transformer.

Did you tried to develop some analog front-end with optocouplers and/or operational amplifiers ?

Re: HP-IL story continues - request for comments
Message #4 Posted by Pavel Korensky on 12 Nov 2003, 4:24 p.m.,
in response to message #3 by Pavel Korensky

Today, I wrote some more software and I have one question.

What features do you want to have in Analyzer mode ?

Currently, I am capturing HP-IL messages and the microcontroller is doing the analysis on message level (message classes, data bytes etc.) and it is sending the informations to the PC via RS-232.

Anyone have some ideas what the analyzer should do ? Triggering on some message ? Higher level decoding (printer, mass storage etc.) ?

Way to go, man! was(HP-IL story continues - RFC)
Message #5 Posted by Giuseppe Marullo on 13 Nov 2003, 3:26 a.m.,
in response to message #4 by Pavel Korensky

Pavel, short form of my comment: see title

Long form: BEWARE: I have yet to see a single printed page about the 41 manuals, so don't flame me too much if you read something completely wrong. I am a rookie here.

HPIL serial dump A HPIL->RS232 "stupid" converter is good, I am interested in building one by myself, but if you have one ready, I will gladly beta test it for you (building one by myself, maybe using a Z8 Encore, a pic or a isopod board. This will avoid me to buy a second HP-41. A bi-directional link would be a plus.

Christoph, please contact me off list, I leave you the guess about what :))

HPIL Sniffer As a sniffer project, you could mimic the features of already available network sniffers, one of the clever one is (was) Expert Sniffer from NAI (formerly Network General). It let you see the same packet of data with different "meanings", one every level, from phisical to application level. It goes even further, diagnosing potential problems, starting from syntoms. Obviously, it is a pricey software, you could simply display the lowest level. Contact me offlist, I could try to write some Windoze code to display frames graphically.

PC CARD "EMULATION" One of the most interesting project I see is a "emulation" of the PC card, so you could connect your 41CV using a serial/usb cable to the laptop without having an ancient ISA bus. One plus could be a support by both EMU41 and the "other forbidden on this site emulator" that should be able to support serial communication with low overhead. Dealing with the serial port is feasible both for DOS applications and windows, so you could bypass problems related to windoze drivers. This is not the same as having the HPIL->RS232 module, obviously. Another choice is USB support, but you could not support dos applications (not easily I suppose). A USB->RS232 should (or better could) do the trick for those that don't have serial ports.

HPIL->YOUNAMEITSTANDARD GATEWAY This could be seen as a gateway to use I2C devices for example. It should be feasible with standard like II2, 1 wire, S.N.A.P. etc.

Isolation & portability : better have it, no dubt.

HPIL CONNECTORS Yes they are a problem, but please avoid DIN, usually they don't have .1 spaced terminals (protoboarding) and the boxing is way difficult. Conecting and disconnecting them stresses the board and it is not easy to build cables.

Maybe a better reasoning is to find a scheme where you don't have to put transformers for every peripheral you put in the bus, something like a bridge (a gateway) between the current loop of actual hp41 peripherals (they already have transformers) and the *new* hpil/ng, where the long distance and low noise are not so important.

Is not possible to separate the standard from the media? If so, maybe the phisical connection could it be quite different from the original hpil. HPIL over TCP/IP?

There is no need (and indeed a lot of problems) trying to keep the same connectors, AFAIK they are not available.

HPIL CHIP Emulating it is excellent, but this is not the only problem, we need to find a suitable replacement for the transformers too. The chips is somewhat available, but what about the transformers?

I would gladly contribute about what I know, as long it is a hobby paced project, and it is in the GPL or low profit spirit.

If appropriate, I could setup a portal where this kind of discussions are held, just not to poison the forum too much with low level details.

Thank you,

Giuseppe Marullo

Re: HP-IL story continues...
Message #6 Posted by James MacPhail on 12 Nov 2003, 6:41 p.m.,
in response to message #3 by Pavel Korensky

An optocoupler receiver sounds like a good idea to me; however you (probably) still want a transformer for transmitter isolation, so maybe two of those is easier. I suspect there are a few people with the equipment to help figure out an easy to make (or buy) pulse transformer replacement.

Another problem will be the connectors... Perhaps someone should establish a standard alternate connector, then only one adapter is necessary? I'd consider one of the readily available configurations of mini-DIN connector (similar to a PS/2 keyboard connector), but a DE-9 would likely be cheaper.

Once you add up the problems of obtaining connectors, the IL chip, and transformers, maybe you end up saying you need to scavenge all the parts?

Good luck!

Re: HP-IL story continues...
Message #7 Posted by Pavel Korensky on 12 Nov 2003, 7:28 p.m.,
in response to message #6 by James MacPhail

This is a question. Is it really necessary to isolate the trasceiver ? We are not talking about development of some commercially manufactured industrial bus. We are talking about the possibility to play with legacy equipment.

The total isolation was perfectly valid during the days when HP developed and manufactured the HP-IL devices. Those devices was used in various environments etc.

But today ? I can imagine the HP-IL loop on the table of some collector, hobbyist or in some area where devices are supposed to do one thing, do it reliably and forever.

The connectors are a problem, you are right. On the other side, you have both types of connectors on each HP-IL cable. So, doing the HP-IL/MiniDIN convertor is cheap and simple. Or better, we can use RJ-45/RJ-11 connectors. They are cheap, you do not need a soldering iron for connecting them to the cable and you can use them also for +5V power distribution.

Maybe I am a bit biased. :-) The main reason for my effort is to have fun and to be able to use my HP-41 in modern environment (like printing the TRACE to my PC, be able to read some old programs from some kind of mass storage or to be able to emulate modules which are too expensive for me on EBay).

Re: HP-IL special parts
Message #8 Posted by Christoph Klug on 13 Nov 2003, 3:10 a.m.,
in response to message #7 by Pavel Korensky

Dear Pavel,

as I told you, I can make available IL-Terminals, IL-transformers and IL-Chips to your HP-IL Mass Storage Unit project. I have some of them in my stock and I need not all of them for completing the rebuild HP-IL/PC Interface Card or the hardware interfacing projects I/O-Board and IL2000 System.

Therefore your project seems to be a nice and advanced application to give some of my parts a new home - soldered to your pcb :-)))

Best wishes from Germany - Christoph

Re: HP-IL story continues...
Message #9 Posted by James on 13 Nov 2003, 4:40 a.m.,
in response to message #7 by Pavel Korensky

Is it really necessary to isolate the transceiver?

I'd guess that if the receivers are fully opto-isolated, then you may not need to isolate the transmitter. Though I would suggest having transmitter protection against short circuits and short to ground and +/-12V (or more)

In the case where the item is some instrument that has other connections to the outside world, then there is the risk that the unisolated transmitter will affect the local ground voltage, distorting measurements, etc.

Using other pins on the loop connector to supply power would help establish a common ground to avoid transmitter/receiver common mode problems. I think it would be a good option for a low power digital system, but it could interfere with sensitive analog measurements. Those could have their own power supply, and if necessary, could be internally isolated from the IL circuitry.

RJ connectors might be a reasonable choice. I find the limited configurations of sockets is a nuisance, and you don't have much choice with the cable, but it is cheap, and twisted pair.

For breadboarding (though one can use flying leads, so I don't feel this is a big problem myself), an 0.050" ribbon cable onto which connectors are crimped is particularly convenient, and gives the choice of easy conversion between dual row headers or DIP plugs (easy breadboarding) and D connectors (cheap, panel mount, and also solder/PCB versions). Long runs can be made with twisted pair/shielded cable.

I suppose this stuff is useful to think about, but until you get close to having a working IL chip replacement, and a quantity of devices to put it in, it may be best to scavenge parts, get some from Christoph, etc. and work on the more immediate/interesting problems.

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