BACnet MS/TP Capture Tool

This tool captures BACnet MS/TP packets on an RS485 serial interface,
and saves the packets to a file in Wireshark PCAP format for
the BACnet MS/TP dissector to read.  The filename has a date and time
code in it, and will contain up to 65535 packets.  A new file
will be created at each 65535 packet interval.  The tool can
be stopped by using Control-C.  The tool can also pipe its output
to Wireshark to be monitored in real-time.

Here is a sample of the tool running (use CTRL-C to quit):
D:\code\bacnet-stack>bin\mstpcap.exe com54 38400
Adjusted interface name to \\.\COM54
mstpcap: Using \\.\COM54 for capture at 38400 bps.
mstpcap: saving capture to mstp_20110413134119.cap
1156 packets
==== MS/TP Frame Counts ====
MAC     Device  Tokens  PFM     RPFM    DER     Postpd  DNER    TestReq TestRsp
0       -       188     4       0       0       0       0       0       0
2       -       189     0       0       0       0       0       0       0
3       -       189     9       0       0       0       0       0       0
7       -       189     60      0       0       0       0       0       0
35      -       188     140     0       0       0       0       0       0
Node Count: 5

==== MS/TP Usage and Timing Maximums ====
MAC     MaxMstr Retries Npoll   Self    Treply  Tusage  Trpfm   Tder    Tpostpd
0       1       0       52      0       11      24      0       0       0
2       0       0       0       0       23      0       0       0       0
3       6       0       50      0       5       100     0       0       0
7       34      0       52      0       5       34      0       0       0
35      127     0       50      0       6       63      0       0       0
Node Count: 5
Invalid Frame Count: 0

The files that are captured can also be scanned to give some statistics:
D:\code\bacnet-stack>bin\mstpcap.exe --scan mstp_20110413134119.cap
Scanning mstp_20110413134119.cap
1156 packets
==== MS/TP Frame Counts ====
MAC     Device  Tokens  PFM     RPFM    DER     Postpd  DNER    TestReq TestRsp
0       -       188     4       0       0       0       0       0       0
2       -       189     0       0       0       0       0       0       0
3       -       189     9       0       0       0       0       0       0
7       -       189     60      0       0       0       0       0       0
35      -       188     140     0       0       0       0       0       0
Node Count: 5

==== MS/TP Usage and Timing Maximums ====
MAC     MaxMstr Retries Npoll   Self    Treply  Tusage  Trpfm   Tder    Tpostpd
0       1       0       52      0       11      24      0       0       0
2       0       0       0       0       23      0       0       0       0
3       6       0       50      0       5       100     0       0       0
7       34      0       52      0       5       34      0       0       0
35      127     0       50      0       6       63      0       0       0
Node Count: 5
Invalid Frame Count: 0

The BACnet MS/TP capture tool also includes statistics which are
listed for any MAC addresses found passing a token,
or any MAC address replying to a DER message.
The statistics are emitted when Control-C is pressed, or when
65535 packets are captured and the new file is created.
The statistics are cleared when the new file is created.
The statistics can be emitted from a file using the "--scan" option.

The MS/TP Frame counts use the following abbreviations:

Device = Device ID when an I-Am is seen in a capture (trigger with Who-Is).

Tokens = number of Token frames sent from this MAC address.

PFM = number of Poll-For-Master frames sent from this MAC address.

RPFM = number of Reply-To-Poll-For-Master frames sent from this MAC address.

DER = number of Data-Expecting-Reply frames sent from this MAC address.

Postpd = number of Reply-Postponed frames sent from this MAC address.

DNER = number of Data-Not-Expecting-Reply frames sent from this MAC address.

TestReq = number of Test-Request frames sent from this MAC address.

TestRsp = number of Test-Response frames sent from this MAC address.

The MS/TP Usage and Timing Maximums use the following abbreviations:

MaxMstr = highest destination MAC address during PFM

Retries = number of second tokens sent to this MAC address.

Npoll = number of Tokens between Poll-For-Master

Self/TT = number of Tokens sent to self (Addendum 135-2008v) and
  number of tardy tokens sent late.

Treply = maximum number of milliseconds it took to reply with
a token after receiving a token. Treply is required to be less
than 25ms (but the mstpcap tool may not have that good of
resolution on Windows).

Tusage = the maximum number of milliseconds the
device waits for a ReplyToPollForMaster or Token retry.
Tusage is required to be between 20ms and 100ms.

Trpfm = maximum number of milliseconds to respond to PFM with RPFM.  It is
required to be less than 25ms.

Tder = maximum number of milliseconds that a device takes to
respond to a DataExpectingReply request.  Tder is required to be less
than 250ms.

Tpostpd = maximum number of milliseconds to respond to
DataExpectingReply request with ReplyPostponed.  Tpostpd is
required to be less than 250ms.

==== FTDI chip RS-485 converter 76800 baud tricks ====

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

Windows XP (from koby3101)
1) Plug in and locate your USB/RSS85 in Device Manager under ports. Right click
on it and select Properties. Click Details tab and from the drop down select
Device Instance Id.

2) Click Start, Run and then type regedit.
Follow this path in the registry
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\FTDIBUS

Locate the folder that has the same name as what you found earlier Device Instance
Id in step 1. Click on 0000 folder and then Device Parameters. On the right
side you will see ConfigData. Right click and select Modify Binary Data.
Locate the 10 27 which in my case were in 5th and 6th position and replace with
27 C0.

This will make the RS485 go to 76800 baud (76923 baud) baud when you ask it
to be 300 baud.

So to capture at 76800 baud type: mstpcap.exe COM2 300

Linux (used with Debian Lenny and Fedora 15)
http://www.connecttech.com/KnowledgeDatabase/kdb309.htm
As root:
Change USB so I can use it later as normal user:
# chmod 777 /dev/ttyUSB0  -
Print current info about the device:
# setserial /dev/ttyUSB0 –a
/dev/ttyUSB0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0
       Baud_base: 24000000, close_delay: 0, divisor: 0
       closing_wait: infinte
       Flags: spd_normal low_latency

Make custom speed:
# setserial /dev/ttyUSB0 spd_cust
24000000/312 gives 76923 baudrate:
# setserial /dev/ttyUSB0 divisor 312
Print to make sure changes got applied:
# setserial /dev/ttyUSB0 –a
/dev/ttyUSB0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0
       Baud_base: 24000000, close_delay: 0, divisor: 312
       closing_wait: infinte
       Flags: spd_cust low_latency

Now as normal user running the mstpcap which uses the default 38400 baud it
will actually capture at 76800 baud. (76923)

Just navigate (cd bin) to bin folder in the project and type:

$ ./mstpcap

==== Named Pipe direct to Wireshark ====

Use the named pipe option to send the capture output directly to Wireshark.
On Windows, use \\.\pipe\wireshark as the name, and set that name as the
interface name in Wireshark.  On Linux, the named pipe name can be just about
any file name, such as /tmp/wireshark.  See:
http://wiki.wireshark.org/CaptureSetup/Pipes

==== EXTCAP direct from Wireshark ====

To use extcap, run Wireshark and go to the About-dialog.
Find a tab located there named "Folders".
Locate the extcap search path.
Copy the mstpcap.exe to that folder, which may not exist.
Restart Wireshark, and look for "BACnet MS/TP on COMx" interfaces.
Configure the interface to change baud rate.
Capture directly from the interface.

==== Developer Info about Wireshark ExtCap ====

BACnet MS/TP uses a DLT (data link type) requested from and
approved by libPCAP development team, which is 165.  Wireshark
includes a dissector that decodes the MS/TP packets when they
use the DLT for MS/TP.  Other DLTs exist for other types, and
there are also DLTs set aside as USER DLTs.

See the following URLs for information about ExtCap:
https://github.com/wireshark/wireshark/blob/master/doc/README.extcap
https://github.com/wireshark/wireshark/blob/master/doc/extcap_example.py
https://wiki.wireshark.org/Development/Extcap
