modbus FreeModbus demo example

This is a port of the FreeModbus Linux demo. It derives from the demos/LINUX directory of the FreeModBus version 1.5.0 (June 6, 2010) that can be downloaded in its entirety from http://developer.berlios.de/project/showfiles.php?group_id=6120.

• CONFIG_EXAMPLES_MODBUS_PORT, Default 0 (for /dev/ttyS0).
• CONFIG_EXAMPLES_MODBUS_BAUD, Default B38400.
• CONFIG_EXAMPLES_MODBUS_PARITY, Default MB_PAR_EVEN.
• CONFIG_EXAMPLES_MODBUS_REG_INPUT_START, Default 1000.
• CONFIG_EXAMPLES_MODBUS_REG_INPUT_NREGS, Default 4.
• CONFIG_EXAMPLES_MODBUS_REG_HOLDING_START, Default 2000.
• CONFIG_EXAMPLES_MODBUS_REG_HOLDING_NREGS, Default 130.

The FreeModBus library resides at apps/modbus. See [/application](/application.md)s/industry/modbus/index` for additional configuration information.