Hi, here goes an update.
Starting the project for the third time.
I am such an organized person I lost my code two times.
Finally got solved the problem os SoftwareSerial not working inside my class. It was a buffer overflow problem with debug to hardware serial.
At this point I have a "multitasking" program which runs: a blinking RGBled on idle state and when waiting for a slave response.
A keypad with a Keyup callback. A serial communication, and a clock with a callback, all running in "parallel".
I think this is it....
I'll be posting the code as soon as it advance a little more on menus...