I've used this guide here to wire my rig : https://groups.io/g/BITX20/wiki/uBITX-Assembly

I've updated the wiring diagram also to provide for all a HD edition, easy to print on paper.

My project is to have the Raduino board not directly connected to the main board. So the idea is to extend the connection with wires.

I've the chance to have some Dupond wires, and here is the cable I've made by soldering the wires to 2.54mm pitch pins :

Not very easy to solder the jack connectors, but now it's OK. It's tiny in the box, because I wanted it as small as possible to transport it easily.