Activating a USB port to enable NMEA data inputs within an older (pre-USB plug-and-play era) was proving a source of frustration. Activating the port via a direct USB feed taken from a protected circuit driven my an Actisense Multiplexer was the intended solution but Open CPN was unable to recognise the USB port on a laptop. Although there are a number of costly solutions on the market but after fitting (the brilliant) multiplexer adding another unit in the chain seemed folly.
Enter the FDIC chip which fools a USB port into recognising RS232 inputs, which are direct NMEA feeds taken from the NMEA bus, converting serial com port data inputs to USB port data.
The introduction of the FDIC chip immediately enabled the NMEA instrument plug-in displays within Open CPN (which itself has been recently upgraded to include more dynamic port settings). The virtual instruments and related functions are active.