The Input Plug is a small board containing a CD4067 16-channel analog multiplexer plus a dedicated ATtiny microcontroller to take care of channel selection. It allows you to connect up to 16 analog inputs to a single AIO pin on any port. There is an “InputPlug” class in the JeeLib library to interface with this board and perform the channel selection.
This board can also be used as 16-channel digital input multiplexer, and even for digital outputs or PWM – with the restriction than a channel goes into high-impedance mode when not selected (there is no latching or buffering).
The Pre-assembled version comes with the SMD-sized CD4067 and ATTiny chips and decoupling capacitor already soldered onto the board. This plug has 16 I/O channels, available via three 6-pin headers. Note that no 6-pin headers are included.
The PCB only variant contains just the board for the Input Plug. No parts, no headers.
As connectors you can use a Plug Headers set with 10 male and 10 female 6-pin headers, which makes it easy to connect multiple plugs and JeeNodes in a “standard” way. Or you can solder the board directly in place for more permanent use.
The documentation and full design details are freely available.