Comments on: Wireshark and BACnet MS/TP

By: Peter

Peter — Mon, 16 Jan 2012 07:36:14 +0000

I’ve modified the program to allow the selection of 76800 as a baud rate as it will work directly with some serial port drivers.
I use the USOPTL4 and it will work for the most part with that – I do get some receive errors on the port which are not being seen by my devices or the router which mey be down to a problem with my hardware setup or the USOPTL4 baud rate not being close enough to 76800 for comfort.

By: skarg

skarg — Sat, 26 Nov 2011 16:35:13 +0000

Thanks for the bug report/fix on the baud rate problem. I have corrected it in the svn repository, and will release new binaries soon.

By: Michel D

Michel D — Fri, 25 Nov 2011 19:54:14 +0000

I forgot to say that this problem is in the V0.6.0

By: Michel D

Michel D — Fri, 25 Nov 2011 19:35:39 +0000

In the main.c file of the mstpcap project, there is an ordering function call problem in the main routine.

The function RS485_Initialize() is called before the RS485_Set_Baud_Rate(). This is why even you want to set the port to an other baud rate than 38400, it always takes the 38400 baud rate.

Just put the RS485_Set_Baud_Rate() before the RS485_Initialize() function and it will do the good job.

By: skarg

skarg — Fri, 14 Oct 2011 22:27:06 +0000

The latest mstpcap utility and friends is available at the BACnet Protocol Stack site hosted by SourceForge.net. Since we still update various things in the tools and in the stack, the download link is a moving target. It is currently at 0.6.0, and can be found here:
http://prdownloads.sourceforge.net/bacnet/bacnet-tools-0.6.0.zip?download

One of the handy things that mstpcap does is display some capture statistics, and so we added the ability to scan an existing capture file and produce those statistics again. The option is “–scan” followed by a space and a capture file name.

I also improved the timing resolution to 1ms on Windows.

By: Trevor

Trevor — Fri, 14 Oct 2011 16:48:35 +0000

I have been trying to get this to work for a little while now and it seems like its my capture program that isn’t working right. When I type in 300 it auto bauds to the 38400 and doesn’t even try to fake the 76800 at 300. I was wondering where I can get the capture program that allows 300 capture.

By: Kris

Kris — Wed, 27 Oct 2010 16:34:30 +0000

Thanks,

In case someone else has problems, I also had to get the latest VCP driver from FTDI’s site to get it to work. The latest driver SerialGear had would not work for me.

Thanks again for all of the great information.

By: skarg

skarg — Wed, 27 Oct 2010 15:40:13 +0000

Here is a procedure that Chad Z. gave me for using the 76800 baud rate by faking a 300 baud entry on FTDI chip-set converters:
1. Delete COM port in Device Manager
2. Unplug USB dongle
3. Delete the following files that are installed by FTDI.
Windows\System32
ftbusui.dll
ftd2xx.dll
ftlang.dll
ftserui2.dll
Windows\System32\Drivers
ftdibus.sys
ftser2k.sys
4. Copy the original ftdiport.ini to another name or location
5. Edit the ftdiport.ini file and change the ConfigData value.

for 300bps = 76677 bps:
HKR,,”ConfigData”,1,11,00,3F,3F,27,00,00,00,88,13,00,00,C4,09,00,00,E2,04,00,00,71,02,00,00,38,41,00,00,9C,80,00,00,4E,C0,00,00,34,00,00,00,1A,00,00,00,0D,00,00,00,06,40,00,00,03,80,00,00,00,00,00,00,D0,80,00,00

for 300bps = 76923 bps:
HKR,,”ConfigData”,1,11,00,3F,3F,27,C0,00,00,88,13,00,00,C4,09,00,00,E2,04,00,00,71,02,00,00,38,41,00,00,9C,80,00,00,4E,C0,00,00,34,00,00,00,1A,00,00,00,0D,00,00,00,06,40,00,00,03,80,00,00,00,00,00,00,D0,80,00,00

6. Plug USB dongle back in and always select “Have Disk” and navigate to ftdibus.inf or ftdiport.inf files which should be in the same folder.

By: Kris

Kris — Tue, 26 Oct 2010 21:22:47 +0000

I’m not understanding how to use 76800 baud rate. Can you please show me what the “HRK,,”ConfigData” line should look like to make an alias where 300 baud is really 76800?

Thanks

By: skarg

skarg — Fri, 08 Oct 2010 14:39:41 +0000

Hi Jochen,

The 76800 is a non-standard baud rate (for personal computers, anyway), and the mstpcap tool is just using the computers serial port for communication. However, some chipset drivers, like FTDI, allow you to create a non-standard baud rate at one of the PC standard baud rates (i.e. 300 baud is now 76800). From the mstpcap.txt file:

If you are using FTDI chip in your RS485 converter, you can alias an existing baud rate on Windows in the FTDIPORT.INF file in order to acheive non-standard 76800 bps:
HKR,,”ConfigData”,1,11,00,3F,3F,27,C0,00,00,27,00,00,00,C4,09,00,00,E2,04,00,00,71,02,00,00,38,41,00,00,9C,80,00,00,4E,C0,00,00,34,00,00,00,1A,00,00,00,0D,00,00,00,06,40,00,00,03,80,00,00,00,00,00,00,D0,80,00,00

replace the 10,27,00,00 => divisor = 10000, rate = 300 bps alias

hex values actual
———– ———
27,C0,00,00 – 76923 bps => divisor=39.125
27,00,00,00 – 76677 bps => divisor=39.000

Then you would run:
mstpcap COM9 300

Note that earlier versions of mstpcap had only the standard MS/TP valid baud rates allowed. The current released version allows any of the standard computer baud rates to be used.

By: Jochen

Jochen — Fri, 08 Oct 2010 10:22:10 +0000

We tried to get the 76800 to work with a FTDI chipset. We tried “mstpcap COM9 76800″ but the mstpcap tells:
mstpcap: Using \\.\COM9 for capture at 38400 bps.

Do have an idea what is going wrong?

By: skarg

skarg — Wed, 19 May 2010 17:43:42 +0000

The application code for the mstpcap utility shows the encapsulation process for a PCAP file format for a WTAP. See the write_global_header() and write_received_packet() functions.

The magic is partly the data link type in the header:
uint32_t network = 165; /* data link type – BACNET_MS_TP */

By: mike

mike — Wed, 19 May 2010 16:47:26 +0000

how to find out the encapsulation process of packets captured in wireshark?

By: skarg

skarg — Tue, 16 Feb 2010 19:56:09 +0000

David asks "Hi, anyone know by chance where I can find information about the protocol Bacnet? I want to know is how to send packets as encoding and decoding, the format has, etc..". The official information is the ASHRAE 135-2008 BACnet standard, available from ashrae.org bookstore. You can use the open source BACnet stack or Wireshark to see how we have encoded and decoded the various services and data in BACnet.

By: David

David — Tue, 16 Feb 2010 18:42:49 +0000

Hola, alguien sabe de casualidad donde puedo encontrar informacion sobre el protocolo Bacnet? lo que quiero saber es como se envian los paquetes, como codificarlos y decodificarlos, el formato que tiene, etc.

Gracias.