Unfortunately, I spent too little time with this project, so now my machine disabled itself (it failed beyond repair). Therefore I discard both the machine and this project.
If you are searching for hints on repairing the machine yourself, or on taking it apart non-destructively, please see Florian Kaiser's website, who has written an excellent documentation on this, and even sells some spare parts.
Regarding the service interface, there has been some discussion in the forum pages at coffeemakers.de. While the serial communications protocol seems to be still unknown, an approach reading directly from an EEPROM storing values of interest has been successfully followed. As I am more interested in starting a brewing cycle through that interface, I should continue researching the serial protocol - as time permits.
For some months, I own a fully automated espresso and coffee machine, the AEG CaFamosa 80. Well, the thing brews wonderful coffee, better than any I have ever tasted before, not taking into account the hand-made espresso in Palermo, Italy. For machine made coffee, after all, I really like this machine.
One day, we discovered another interesting feature of this machine: It has an interface, obviously meant for service technicians to connect some diagnostic device, and reading out counters, tuning parameters, and such. This was interesting for us, geeks that we are.
First, I searched on Google for that coffee machine to see, if anyone already connected something else, a computer for example, to that interface. This yielded nothing, but I found out that these machines are actually built by Eugster/Frismag AG, Switzerland, and just labeled as AEG machines. OEM-ware, one could say.
Then I tried, without any hope for success, sending an email to AEG's support department -- and they indeed sent back a mail with some drawings of the CaFamosa's casing and internals. With this, in theory, one might have a chance of taking the machine apart without causing any harm. Thanks to AEG for that! Unfortunately, they could not (or did not want to) give me any information on the service interface.
(Please note: On this coffee machine (at my home), there was only an internal service connector without a plugged hole to the outside. The machine was not sold with a DB9 connector, and I surely have voided any warranty by adding it.)
Now time had come to do some more sophisticated analysis on our own. Because it is so sophisticated, I have split it up to some more pages... First, we digged up some multimeter and did some measurements on that service port: Measurement info.
After having found one GND connector, we wondered what use the other lines
were. As this was not really clear from the measurements, we decided to
take the machine apart to have a closer look at the electronics driving the
machine and the service interface.
And so we did.
This has one (small) advantage: If they had told me things, I would not have published that information here. If we find it out on our own, I do not feel publishing the findings can be wrong...
This is work in progress, and I will write this section as soon as there is some more information to publish.
New findings and thoughts: