In the era of legacy PCs with on-board RS232 COM Ports, it was common practice to establish a simple communications network between PCs using a cable popularly known as a Null-Modem cable. Typically, such a cable would have DB9 female connectors on each end with the TX / RX and handshaking signals cross-connected so that the PCs could communicate with each other via legacy COM ports.

On modern PCs, the legacy COM Port connector is rapidly disappearing as USB becomes the multi-function communication port of choice. However, this presents a dilemma in application areas that previously relied on legacy COM Ports for inter-PC communication.

A convenient solution to the problem is this FTDI USB Null Modem cable. From the outside, this cable appears to be two USB type “A” sockets wired together, however each of the USB sockets conceals a small PCB with an FT232RQ-based USB-UART converter IC plus support components inside. The interconnect cable cross-connects the TXD / RXD data signals, RTS / CTS handshaking signals and interconnects the common GND reference rail between the two converter PCBs.

When used together with FTDI’s supplied Virtual COM Port (VCP) drivers, the USB NMC cable may be used to establish inter-PC COM Port based communication at baud rates of up to 3M baud. The USB Null Modem cable comes with an interconnect length of 2.5m (8.2ft). Multiple operating systems are supported including Windows, Linux, Mac OS etc.

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