Olivetti Logos 262 PD desk calculator - a candidate

At a 2nd hand shop I bought a working desktop professional calculator just because it has a VFD display. It is an Olivetti Logos 262 PD, with the printer, which is working too.

My idea is to turn the calculator into a clock by intercepting keyboard signals and typing in digits from an Arduino. This device comes with an enclosure and a suitable integrated power supply, so once the electronic hardware&software work is done, it will be ready for public display.

Since there is no schematic to be found, I will have to do some reverse engineering of the keyboard protocol. Unfortunately it is connected straight to the large microcontroller IC, so there is no "bus" to attach to.

There are 17 lines and 56 keys, so there'll be a good deal of work to draw a map.