Beyond Logic

RS-232 Protocol Analyser

In need for a cheap but effective RS-232 Protocol Analyser? Just make your own Y adaptor to enable the logging or display of data transmitted and/or received in ASCII, Hex, Decimal or Hex-Dump formats. A configuration file is included to allow quick setup and analysis.

The Protocol Analyser running in HexDump Mode

The Protocol Analyser running in Hex Mode.
The white text shows transmitted data, while the yellow is received data.

Wiring of the Y Cable

You can make your own "Y" cable by following the diagram below. It consists of a pass-through cable which is connected in-line with the link under test. The TXD and RXD lines are broken out and sent into a second "Protocol Analyser" computer via two com ports, each monitoring one line each. The second computer then runs the Protocol Analyser Software.


  • Version 1.0, 18K bytes.

  • Copyright 2002-2005 Craig Peacock - 15th June 2005.