Check out this fully-assembled Raspberry Pi GPIO shield that offers a number of handy advanced features for your Raspberry Pi. From Amescon.com:
Just plug the RasPiComm on the GPIO header of your Raspberry Pi and start using advanced features like a realtime clock (your Raspberry Pi won’t lose time when powered down), a 5-way joystick, outputs and two serial ports (RS-232 and RS-485). Directy control a display, a stepper motor controller or relays and much more!
The main features
- RS-485 port (control stepper motors and other cool stuff)
RS-232 port (easily talk to your computer or other serial port devices like a modem)
- real-time clock with battery backup – never lose time again when powering down your Raspberry Pi
- direct I2C connector – directly connect a display or sensors
- 5-way joystick – control your Raspberry Pi easily
a tiny piggyback board – no extra cables or space
- Full API support including drivers for an OLED display, an advanced stepper motor controller and a deamon for remote controlling your RasPiComm via Ethernet or WiFi
- Fully assembled including the backup-battery, ready to go! just plug it in!