HP-25C Eumulator

[Chris Chung]

(10-22-2014 08:51 AM)Harald Wrote:  I have installed the LEDs, a CR2032 and switched it on - with no success...
Seems like the switch has not survived in the mail. Maybe you can protect that with some extra padding for the next shipments.
Anyway, after replacing the switch everything works fine now

Which brings me to my Questions:
The simulator always comes up as a HP21 when I turn it on. I worked out that by pressing <g>, <sigma+> or <Clx> on power up I can switch to different roms. But is there a way to make the selection permanent? And also is possible to save the program in flash memory?

Do you mean the power slide switch? Does it look physically damage (due to shipping) or just did not close properly when slide into position (part quality) ? I usually order parts that are easy to get and they may not be the highest quality.

I had similar issue w/ the DataMath calculator (which 20+ people built) where when it was turn on, nothing happened. It turned out to be caused by the key scanning, the initialization code thinks that a key had been pressed and waited for it to be release, thus cause a freeze in S/W. It can be caused by faulty tactile buttons (always on), bad soldering / traces (shorts) and (more common) fingers touching the back traces on the PCB (stray capacitance registered by key scan). I also forgot to put tape to insulate the pcb back better on your unit. You may experience jumping buttons but you can avoid it insulating the pcb back w/ any plastic / tape. See photos from my previous posts.

Yes, you can setup a "default" rom + speed via menu. I had updated the README at my github repository w/ these simple operation guide

press-n-hold 1st row, 5th column (from top) for hp33C
press-n-hold 2nd row, 5th column for hp25C
press-n-hold 3nd row, 5th column for hp21
press-n-hold 4th row, 4th column for version info
press-n-hold 1st row, 4th column to show greetings
press-n-hold 1st row, 3rd column to edit greetings, use 0-9 to enter numbers and letters, Run/Stop to advance digit, Cls to abandon entry
press-n-hold Pgm/Run toggle button to edit default startup settings, use 'F' key to select rom, 'G' key to select speed, Pgm/Run will save setting and exit setup

The setup mode, i.e. RPM/RUN + switch on, also tests the tactile buttons, it shows an internal scan code at the last 2 digits. Handy when you are building your own or checking the H/W.

The "edit greetings" mode, pressing numerics consecutively (like old phones) will give you alphabets.

I spent last evening on these. Once Harald indicates there are no major issues on the firmware, I had these 4 units ready. The firmware is frozen (function-wise) and I can only make small adjustments and bug fixes. I had tried to squeeze in all-things-possible and there is only some 50 bytes left out of a 16K bytes space.

I am still waiting for some tactile buttons and some sets of LEDs for the rest (another 3 units).

My kitchen table factory. Left, after 5 hours of work start to program the MCUs. Right test run, setup menu on all.