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HP Forum Archive 20

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HP-41 Unknown Interface
Message #1 Posted by Juergen Keller on 27 Aug 2011, 11:23 a.m.

Somebody pointed me to this HP-41 with an unusual custom interface, see pictures. Has anybody seen such an interface before? Or does anybody even know what it is for? Any hints and suggestions welcome!

      
Re: HP-41 Unknown Interface
Message #2 Posted by Mark Hardman on 27 Aug 2011, 12:58 p.m.,
in response to message #1 by Juergen Keller

I looks like a cereal port used to dispense the barley for your lager unit. <Ducks>

            
Re: HP-41 Unknown Interface
Message #3 Posted by Walter B on 27 Aug 2011, 1:13 p.m.,
in response to message #2 by Mark Hardman

:-D Oh yes, such ports are really a big help for mankind. What a progress along the lines of consumer interest!

      
Re: HP-41 Unknown Interface
Message #4 Posted by Randy on 27 Aug 2011, 4:52 p.m.,
in response to message #1 by Juergen Keller

Based upon the position of the wires that I can see connected, the interface is a simple extension of the keyboard row and column matrix, allowing external switches to input data into the 41.

      
Re: HP-41 Unknown Interface
Message #5 Posted by Andrés C. Rodríguez (Argentina) on 27 Aug 2011, 4:57 p.m.,
in response to message #1 by Juergen Keller

Just guessing, it may be a "paralell keyboard matrix" interface, in which external switches simulate keypresses. A 3x3 matrix, allowing (for instance) for digits 1 to 9 (but not 0) can be done with six wires, as shown.

If someone wanted to export the HP41 bus signals (clocks 1 and 2, Flag Input, Data, ISA) it would had make sense to pick them at one of the backplane ports

Again, this is just a quick guess.

            
Re: HP-41 Unknown Interface
Message #6 Posted by Howard Owen on 27 Aug 2011, 5:28 p.m.,
in response to message #5 by Andrés C. Rodríguez (Argentina)

There appear to be three more wires, terminating somewhere on the reverse side of the circuit board. It's nine pins, built inside what looks like an HP/IL female connector.

                  
Re: HP-41 Unknown Interface
Message #7 Posted by Andrés C. Rodríguez (Argentina) on 27 Aug 2011, 6:58 p.m.,
in response to message #6 by Howard Owen

With three more wires a 5x4 matrix is possible, allowing for numeric data, decimal point, R/S and some more...

      
Re: HP-41 Unknown Interface
Message #8 Posted by Ángel Martin on 28 Aug 2011, 2:24 a.m.,
in response to message #1 by Juergen Keller

Wow, that's elaborate hacking - wonder if it's part of a data input mechanism different from the original keyboard - maybe an industrial bar-code reader?. I have no recollection of such being published anywhere, but yet, the 41 series was such a versatile platform - and this proves it again.

Edited: 28 Aug 2011, 2:59 a.m.

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