What is serial communication? – Download PDF version

RS232C Interface – Download PDF version

Fundamentals of RS232C Communication – Download PDF version

Introduction to Serial Communication – Download PDF version

Using the Fieldserver to Snoop on a RS-232 Line. – Download PDF version


Frequently Asked Questions (FAQ)

What are BACnet Device Backup and Restore Procedures?

  • The automation developer should be aware of the BACnet procedures concerning device Backup and Restore activities. Both procedures are defined in detail by the standard in Clause 19 for future reference. The procedures may involve either network visible BACnet objects and/or non-network visible settings. Backup…Read More 


How often should a BACnet MSTP device search for a new master?

  • A BACnet MSTP device should search for a new master after it has gotten the token more then Npoll – 1 times. If your device is on a large network (20+ nodes) and Npoll is set to a very high number it may take a long time for your device to find a new device between its own MAC address and its next station. For …Read More 


What is RS232 Serial Port Sniffing / Snooping?

  • Have you ever needed to snoop a RS232 serial port to observe the messages passing back and forth? It’s easier than you thought. All you need is application called HyperTerminal and the simple cable below. The cable can be assembled in minutes and requires a couple of diodes which you can probably buy…Read More 


Why can’t I change to 76800 baud rate on PC?

  • The reason for this is that the the standard 16C550 PC UART is too slow to keep up with the signals coming in and out. 76800 is not a standard multiple of the UART clock frequency. Devices can be customized and…Read More 


How to Reduce latency on com ports?

  • When a BYTE is sent from a serial device (BACnet MSTP thermostat) to a USB to 232/485 converters (USB-COMI-SI-M) it is cached on the USB converter until one of two things happened. Transfer size – More then x BYTES are collected or Latency timer – More then n Milliseconds (ms) expirer. By default…Read More 


CAS Gateway UL RS232 to RS485

  • To switch the CAS Gateway UL box from its default RS232 to RS485 you will need to open the box and change some of the jumpers. For example this is a photo of the board set up in RS-232 …Read More 


What is RS-232 Mini Tester?

  • How to know which RS-232 data lines are active? The RS-232 Mini Tester is an efficient device to connect in series with any RS-232 interface for testing a serial (RS-232) link. An example of how an RS-232 mini tester looks like is shown in figure-1 below. Figure-1: RS-232 Mini Tester The…Read More 



RS232 Specifications and standard

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