HP Forum Archive 20

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New Interface for HP-28S ? Message #1 Posted by robertoataulfo on 10 Sept 2011, 2:30 p.m. Interface for HP28S

Re: New Interface for HP-28S ? Message #2 Posted by Howard Owen on 10 Sept 2011, 2:53 p.m., in response to message #1 by robertoataulfo Looks like it might have an IR receiver. There's no way this could be bidirectional, so the statement that you can "send the data from the computer" has to be wrong. But a print to text algorithm might be possible to save HP-28S data, including programs. But since you can't reload them without keying them in again, the statement that this device will prevent you from "loosing [sic]" them is also misleading.

Re: New Interface for HP-28S ? Message #3 Posted by Eric Smith on 10 Sept 2011, 7:24 p.m., in response to message #2 by Howard Owen I owned one of these years ago. It is an IR receiver for the HP 82440A/B printer infrared protocol. It does NOT do IRDA or any other infrared protocol. It will NOT work with a USB-serial adapter, and it needs specific DOS software which will NOT work correctly under any version of Windows.

Re: New Interface for HP-28S ? Message #4 Posted by Christoph Giesselink on 12 Sept 2011, 1:50 p.m., in response to message #3 by Eric Smith Quote: I owned one of these years ago. It is an IR receiver for the HP 82440A/B printer infrared protocol. It does NOT do IRDA or any other infrared protocol. It will NOT work with a USB-serial adapter, and it needs specific DOS software which will NOT work correctly under any version of Windows. Hi Eric, do you know if this product has an own CPU? There was a similar product end of the 80'ies in Germany called PrintHP. This product consists of a dumb IR receiver sending the decoded 32KHz bursts to the PC CPU over the RS-232 CTS input line. Therefore you needed also pure DOS, the special receiver software and a PC not faster than 80386 or an early slow 80486. Christoph

Re: New Interface for HP-28S ? Message #5 Posted by Eric Smith on 13 Sept 2011, 10:53 a.m., in response to message #4 by Christoph Giesselink It does not. It just has an IR receiver driving one of the EIA-232 handshake lines. That is why it won't work with Windows.

Re: New Interface for HP-28S ? Message #6 Posted by Raymond Del Tondo on 10 Sept 2011, 7:36 p.m., in response to message #2 by Howard Owen Slightly OT, but actually you can perform serial I/O on the HP-28S ;-) A few years ago Christoph Giesselink demonstrated serial I/O using an HP-28S (which I donated to him for exactly these tests) . He used the pins of the IR transmitter to send _and_ receive data. The whole proof of concept is documented. If interested please ask Christoph for more details. IIRC the driving idea behind this was to elaborate whether serial I/O could be implemented on the HP-42S. I think it would work, but then there were other projects... Ray

Re: New Interface for HP-28S ? Message #7 Posted by Bart (UK) on 13 Sept 2011, 5:28 a.m., in response to message #1 by robertoataulfo Looks indeed like a receiver for the 28C/S. If you manage to get it working you can indeed prevent losing the listing of programs, but in case of calculator "memory loss" you'd have to re-type it into the calculator. If you really want to try bi-deractional I/O, here's a project on HPCalc: HP-28 I/O

Re: New Interface for HP-28S ? Message #8 Posted by Christoph Giesselink on 13 Sept 2011, 1:41 p.m., in response to message #7 by Bart (UK) Quote: If you really want to try bi-deractional I/O, here's a project on HPCalc: HP-28 I/O I read this file some years ago. I still find it silly to use one contact of the keyboard matrix for input. ;-) My solution use the '+' pin from the anode side of the IR-transmitter LED, the signal pin from the cathode side of the IR-transmitter LED and GND from battery minus. The "trick" is using the IR-transmitter signal pin for both directions; quite nobody knows that the LED driver is a bidirectional pin. Christoph

Re: New Interface for HP-28S ? Message #9 Posted by Howard Owen on 13 Sept 2011, 5:38 p.m., in response to message #8 by Christoph Giesselink Quote: The "trick" is using the IR-transmitter signal pin for both directions ... Half duplex. :)

Re: New Interface for HP-28S ? Message #10 Posted by sylvandb on 13 Sept 2011, 9:02 p.m., in response to message #9 by Howard Owen Quote: Half duplex. :) Half duplex is infinitely better than one way...

Re: New Interface for HP-28S ? Message #11 Posted by Howard Owen on 13 Sept 2011, 10:37 p.m., in response to message #10 by sylvandb Agreed. :)

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