Before I used to work with Arduino, I used Conrad C-Control Station as prefered compact controller. The advantage of C-Control Station is that it comes in a case, has an RS232 port and is equipped with screw-type terminals for connections. I often need a device like this, where I can connect push buttons and sensors direct and have RS232 to control something. I didn't find a Arduino compatible equivalent, so I started and developed it by myself. The result is a compact design that is easy to copy. I call it V-IO.
V-IO is open source hardware, all files necessary to produce the device (Target project file, Gerber files, DXF construction files) are available at www.vman.cc/v-io/en
. The UART can be switched by DIP switches between USB and RS232 (TTL to RS232 Level converter is included). That makes the shield very flexible to use. It can run as interface for a computer (using USB) or stand alone and control something via RS232. V-IO has screw-type terminals to make it very easy to connect sensors and buttons. To have a compact design, I use only 12 pins of the build in Arduino Uno. All ports can operate as digital I/O, 6 can work as PWM and 6 as ADC alternatively.
Feedback is welcome