Some RS485 shields are already available for the Raspberry Pi on the market, but these extensions are not suitable for professional use, because they come without a galvanic isolation between the RS485 bus and the Raspberry Pi. Without such isolation a damaging of the Raspberry Pi or malfunction of the device is possible, because of the large distances of a RS485 bus. Furthermore a full-duplex mode (RS422) is also not integrated.
The shield comes with a lot of additional features:
- RS485 mode (half duplex)
- RS422 mode (full duplex)
- galvanic isolation between Raspberry Pi and connected RS485 bus
- enhanced ESD protection
- adjustable automatic transceiver switching for RS485 mode
- adjustable control of transceiver/receiver via GPIO pin
- adjustable Pull-Up, Pull-Down und terminating resistors
- indicator LEDs for RX and TX
- removable block terminal for bus connection
- many options adjustable via DIP switches
The RS485 is in use in many applications like
- industrial and home automation (for example MODBUS)
- lighting control (DMX)
- maritime and navigation controls (NMEA0183)
- video surveillance (for example Pelco D)
If you like to know more about RS485 visit this website: http://www.radio-electronics.com/info/telecommunications_networks/rs485/rs-485-tutorial-basics.php
