After a second test resulting in a working display yesterday evening, my 2nd attempt to get a breadboard version of K3NG’s Arduino CW keyer up and running turns out to be a success!
This morning I soldered a female mini-jack and a speaker to the Arduino Nano and set the right pins in the Arduino IDE. After a upload/reboot the keyer came up and it works perfectly!
I really like this Arduino stuff. It is simple to figure out and the fact that it is open source (software as well as hardware) makes things easy and quick to work with. Hats off to the author of the keyer code: K3NG Radio Artisan.

I still have to try connect the keyer to a rig. The fact that you can use one paddle to key multiple rigs, I think is ideal. That way I never have to unplug my paddle from the TS-590 and plug it in the Elecraft K1 or the other way around. You can even connect as much as eight rigs! I don’t think a Arduino Nano has enough connections for it, but the software can do it.
Actually I think I will buy a Arduino Uno for this project so I have enough connections for all kind of options to activate. As controller I considering a rotary encoder. A separate power supply is needed too as you can see the display dimmed when the speaker makes sound.
And then the hardest part; find and build the whole thing in a nice case!