Decoding data going to a 4-bit display.

Hey there,

I am not new to arduino projects, yet have never really dived deep into how things actually work in there.
And I am trying to tackle something crazy for my level of understanding right now.

I need to read data going to 8x2 4 bit OLED - WEH000802ALPP5N00000

I am reverse engineering this device and have access to the RX/TX lines, but they seem to be using some custom protocols and that would be a project for later.

So...for now, to build a proof-of-concept, I am need to get the data out of this display and use it as variables in my own code.

I found a similar project to mine here - Read data from LCD (4-bit mode) - Displays - Arduino Forum
but the guy has lost the source code, nor remembers how exactly he did it.

I am open to any pointers as where to start.

follow 6v6gt what he is doing... LCD 1602 (and similar) databus sniffer - Exhibition / Gallery - Arduino Forum