evolution of freeModBus library v1.5 to 2.0:
- provide supoprt of multiple port instances, with legacy compatibility
- a bit fix, ports on ContikiOS, port ВМ10Я+uOS, LPC176x+RTEMS
freeModBus implements light-weight modbus server and client
daemons on embedded low-profile mcu, with non-blocking async-io