Serial Connections.
Serial port
debug technology.

Serial port debug technology

In this article we will discuss in details the most important aspects of debugging serial connections.


Devices that require RS232 interface for serial port communication are plenty. They include most of equipment used in laboratories, quality and process controllers, various sensors, measuring instruments such as scales and a lot more.

Despite the standard being so popular it is not easy to debug RS232 connections. You have to take into consideration a number of aspects such as hardware and cabling, communication settings and protocols – any mismatch here can cause a problem. To successfully debug serial interface, i.e. to detect and solve issues at an early stage, it is important to view the data stream, and this is possible with the help of special software – Serial Port Monitor by Eltima.

Serial Port Debugger

Serial Port Monitor - a high-quality COM port debug utility that can log, display and help you analyze serial port communication in the system.
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Serial Port Monitor

Log and analyze serial port activity
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Serial Port Monitor

Connect to a correct COM port

If your computer is equipped with several COM ports, make sure to choose the correct one. If in doubt launch Device Manager and check ‘Ports (COM & LPT)’ section, it should display a list of ports installed in the system including virtual ports, if you’ve got any.

Choose a suitable cable

The cables you use to connect to the port also matter. A typical cable would have at least three wires – transmit and receive lines and a signal ground. Some devices might require additional lines for controlling the data flow, e.g. for ‘hardware handshaking’ (RTS/CTS or DTR/DSR data flow). If you don’t have additional wires, you won’t be able to communicate with device.

The two major cable types are ‘modem cables’ and ‘null modem cables’, the difference between the two is that in the former the wires go straight through, while in the latter they are crossed.

Configure communication parameters

There is a set of parameters that needs to be configured for the communication – baud rate, parity, number of data bits, stop bits, flow control, etc. Your communication software usually overrides the parameters set by Windows Device Manager.

Serial Port Monitor makes this task easy, thanks to user-friendly interface and intuitive navigation you do not need any programming skills to get the settings right and debug serial port.

Execute the communication protocol

Protocols vary in their complexity, and there is no standard for communicating with a particular device or class of devices. Typically simple protocols will require a text command for a device to transfer data, and data received will be easily readable in a text editor. You can even have a button on a device, pressing which will initiate data transfer. More complex protocols might need some calculations and setting up responses, data received via such protocols might need to be converted from a binary value to be read by humans.

In short, the least you should know to debug port is what command you need to send to a device and how to interpret data received from a device. For more details you can refer to the device manual or contact the manufacturer of a device.

Execute the communication application

Now when you are done with setting up the connection, you can start using Serial Port Monitor for transferring data to or from a serial device. The software allows collecting and displaying data exchanged between a device and app. Apart from that, it offers extra features such as filtering out and searching for relevant data, and exporting data in a number of formats. You can use built-in terminal for implementing text commands and make most of the clean user interface, a bonus to using Serial Port Monitor.

Serial Port Monitor

This serial port debugger is powerful yet compact and easy-to-use and. It enables exploring the OS, as well as monitoring serial ports for the purpose of detecting problems with the system, applications and processes.

For more information, please visit the software’s web page.

Olga Weis 29 March at 14:41
Olga Weis 27 Apr at 15:12
Olga Weis 25 May 17:09