HP-25C Eumulator
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09-29-2014, 04:50 PM
(This post was last modified: 09-29-2014 04:52 PM by Chris Chung.)
Post: #20
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RE: HP-25C Eumulator
I had upload the code to github for anyone who wish to have a look. They are not very well organized though.
I assembled the latest design over the weekend. I had a bad trace and the original design is not very bright (having to multiplex 12 digits) on a 3V cell. So this newer design I use 2 x 3V power and used a LDO regulator to fix the supply to 3.3V. It is only a bit brighter. Right now the key-scanning is very "jumpy" and keep registering wrong key-press and key-release events. I have to spend time to work on the scan timing. One interesting feature of the HP-25 is that when you press down and hold the "R/S" run button, it show the current program step, and only when you release that button, the program starts. To re-create this feature, I have to use dedicated io scan lines and do some s/w tricks. The attached image shows the old and newer (right) version PCB. /EDIT forgot the source link, here https://github.com/simpleavr/NP25 |
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