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HP-41 GPS Module - True or fiction?
11-07-2016, 12:51 PM (This post was last modified: 11-07-2016 03:30 PM by Maximilian Hohmann.)
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RE: HP-41 GPS Module - True or fiction?
(11-07-2016 11:56 AM)Ángel Martin Wrote:  You should see the GPS running on the HP-25 with a new ACT circuit, maybe that would convince you that there's nothing wrong with spicing it up with modern tools...

I didn't say there's anything wrong! And as I tinker around with electronics in my spare time (maybe to 1/10 of Panamatik's level...) I may one day put an Arduino board an a GPS sensor into a dead HP-21 or 25. But this will be a completely different calculator then. Only the keyboard and display will be original, the "heart and brain" of the machine, which made it a priced collector's piece, will be gone.

It is like restoring the Mona Lisa to modern standards by painting a contrail into the sky. This will certainly appeal to some who like the thought of bringing old and new together, but the majority of art lovers will burst out in tears.


NB: Out of curiosity, I wired together a little GPS receiver with stuff pulled from my box(es) with parts. This is a minimal Arduino based solution using a 10Euro Chinese GPS module and an 8 digit seven segment display. The module outputs a serial ASCII data stream (NMEA), libraries for parsing that stream can be found plenty on the internet. It took a couple of minutes after power-up to get a fix, but it hasn't been powered for months. If I switch it on and off again now, it should get the fix within seconds.

[Image: IMG13266.jpg]

To see if it will fit inside an HP-41 module, i put it next to a printer connector (I misplaced my box with real HP-41 modules... but I know I have it somewhere). This module here, especially with the external antenna, is probably a little bit too large:

[Image: IMG13270.jpg]

But I have smaller ones too (the one here is for my quadcopter drone), the antenna is fixed to the back of the PCB but can be desoldered and placed anywhere. A module like that might just fit inside a normal module, certainly so if the antenna is mounted on the outside.

[Image: IMG13267.jpg]

[Image: IMG13268.jpg]

[Image: IMG13269.jpg]

Processor-wise, all that is required are two wires, TX and RX for a 9600baud serial connection. An ATTiny chip could possibly be used for that, it comes in an 8pin DIL package and would have 4 digital I/O lines left to communicate with the calculator.
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RE: HP-41 GPS Module - True or fiction? - Maximilian Hohmann - 11-07-2016 12:51 PM

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