Brian Gaff laid this down on his screen :
Oh whats one of these then?
I see the name no idea what it is.

It is a really tiny 16Mhz processor, memory and some i/o on a PCB
around 2" x 1", with a USB interface built in, which enables you to
plug it into a PC to program it. which like the RPi has quite a
following. £8 delivered, complete with leads.

Plan is to plug it into my heating systems Ebus, then maybe my Rpi
feeding data to my PC, or direct to PC, so I can see what my heating
system is doing. Just an interesting project, for my own amusement and
no great cost if it doesn't work..