[time-nuts] Re: FE-5680A Adjustment board

[Bob Camp]

Hi

Very Cool !!!!

I would suggest doing some careful photo’s of the inside of *your* unit. There are a mind boggling number of variations on these units. That makes any statement about “mine is the same as his” a risky thing. You just never can be sure ...

Bob

> On Nov 21, 2025, at 4:58 AM, Luca Pandolfini via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Hello,
> This is my first post. :)
> I found many old posts about the topic but to my knowledge none seems to
> include this content, AFAIK.
> I happen to have almost completed the majority of the reverse engineering
> of the Temperature-controlled voltage "Adjustment Board" of an (old?)
> FE-5680A (Since there are many different version, I am talking about the
> exact model shown in this page:
> http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%201_1.pdf
> ).
> 
> If anybody is interested, I can share one or more of the following items:
> - "pseudo-schematics" of the board,
> - decompiled and (mostly) annotated microcontroller code
> - description of the (full set? of) serial commands
> - memory and EEPROM maps
> - Temperature/Voltage calibration values
> 
> I started the project as a fun way to refresh my 8051 assembly skills and
> play with useful tools while doing so (e.g. dumping the SPI EEPROM with a
> BusPirate, dumping the PSD ROM with an Arduino, learning to use Ghidra,
> etc...).
> Since it might take quite a bit of time I just wanted to have feedback from
> the community and know if it might be worth tidying up this material (but
> only if there is some interest, since it looks like a device becoming
> obsolete...).
> Please let me know what you think and greetings to everybody!
> 
> LucaPandolfini
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