HP-25C Eumulator
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09-22-2014, 06:09 PM
Post: #10
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RE: HP-25C Eumulator
Thanks Eric for the original nonpareil work! I tried to email him but has not yet got a reply, may be his site / account is not very active these days.
It sounds interesting that there are a lot of non-working 20's. I googled some pictures on the internals and this is what I think. The led module can be made to work as they are all the same, segment + multiplexing. However, the "comma" is not available on my design as I ignored it because of lack of IO pins and my Sparkfun led module has only 7 segment + decimal. The keyboard, however, need more investigation. I am doing a 12 x 3 matrix scan (based on 12 digits as columns, I used 3 IO pins dedicated to the row scan), I don't know if the original HP layout is like so. I will investigate though. The fact that it will require considerable de-solder, soldering to perform the "brain transplant", not every one may have the resource to do it. I was initially thinking of throwing away everything (including keys and led module) and snap in a PCB (like what I had prototype), just make use of the case and plastic key-tops. I will come up w/ a schematic for your comments later. |
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