| Author |
Message |
Daniele
Guest
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 Posted:
Tue Nov 29, 2005 4:46 pm Post subject:
Monitoring RS485 |
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Hi all,
i need an informatio about rs485:
I need to watch netwrok trafic from my device and another device that
use rs485 to comunicate. Is possible to connect in parallel mode
another peripherical (like a pc via rs232) to trace all the message
that is exchange from two device?
Thanks in advanced
Daniele |
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Anton Erasmus
Guest
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| Posted:
Tue Nov 29, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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On 29 Nov 2005 02:46:06 -0800, "Daniele" <daniele.gadaleta@gmail.com>
wrote:
| Quote: | Hi all,
i need an informatio about rs485:
I need to watch netwrok trafic from my device and another device that
use rs485 to comunicate. Is possible to connect in parallel mode
another peripherical (like a pc via rs232) to trace all the message
that is exchange from two device?
|
RS485 does not specify the protocol used. Connecting an RS-485 buffer
such as a MAX485 or similar is not a problem. (Keeping things such as
stubb lengths etc. in mind). If the protocol used is asynchronous
serial, then adding an RS-232 buffer such as a MAX232, and then
connecting this to a standard PC serial port is all that is needed.
Plus software of course.
Regards
Anton Erasmus |
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Noway2
Guest
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| Posted:
Tue Nov 29, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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I have used a home made device, along the lines of Fred's description,
to do exactly what you are asking. The device tapped off of the rs-485
lines with a cmos inverter and then fed the inverter output to a rs232
driver. Jumpers were used to select one or two inversions as
necessary. using two of the devices, and a program I haven't been able
to locate (though I wish I could - it was called something along the
lines of datascope or pals), I could monitor both the recieve and
transmit channels simultaneously.
I would imagine that there are commercially available tools available
for this purpose, but I have no idea how much they would cost, but
probably a lot. You could probably make up your own circuit easilly
enough, but then you would still need to find a monitoring program. |
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Fred
Guest
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| Posted:
Tue Nov 29, 2005 5:16 pm Post subject:
Re: Monitoring RS485 |
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"Daniele" <daniele.gadaleta@gmail.com> wrote in message
news:1133261166.326280.232030@g14g2000cwa.googlegroups.com...
| Quote: | Hi all,
i need an informatio about rs485:
I need to watch netwrok trafic from my device and another device that
use rs485 to comunicate. Is possible to connect in parallel mode
another peripherical (like a pc via rs232) to trace all the message
that is exchange from two device?
Thanks in advanced
Daniele
|
Use a MAX485 or similar to convert the signals to TTL RS232 and then a
MAX202 or similar to get back to true RS232. With luck your serial port
might take the TTL levels. The baud rates for most application are
generally the same as standard RS232 baud rates. You might have to check
with a scope if not sure. Then use a RS232 terminal emulator of some sort.
HyperTerminal in WinXP is one example. |
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Jim
Guest
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| Posted:
Wed Nov 30, 2005 12:13 am Post subject:
Re: Monitoring RS485 |
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| Quote: | i need an informatio about rs485:
I need to watch netwrok trafic from my device and another device that
use rs485 to comunicate. Is possible to connect in parallel mode
another peripherical (like a pc via rs232) to trace all the message
that is exchange from two device?
|
I've done similar. RS485 to RS232 converter. Used to capture RS485 data.
Used a scope to find the data rate and wrote the converter software to
simply package up the received RS485 data and send out as RS232 for logging
on a PC. You end up with lots of data but making sense of it is another
matter. I had part of the original protocol document and needed to fill in
the gaps so it was fairly easy.
If you need general RS485 info or need to purchase an RS485 to RS232
converter try www.rs485.com . Best site on RS485 I've ever found.
Good luck
Jim
www.picmodules.com |
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Daniele
Guest
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Dave Hansen
Guest
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| Posted:
Wed Nov 30, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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On 30 Nov 2005 06:00:12 -0800 in comp.arch.embedded, "chris"
<cruff@cts.com> wrote:
[...]
| Quote: | i have always used my olg greenleaf VC.EXE program to see side-by-side
output from my sniffer hardware.
greenleaf is alive and well at:
www.gleaf.com
|
Comlite32 is a free tool from www.rtcard.com that lets you monitor COM
traffic in your Windoze box. Not a terminal program, but lets you
watch the communications traffic.
Regards,
-=Dave
--
Change is inevitable, progress is not. |
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chris
Guest
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| Posted:
Wed Nov 30, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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Noway2 wrote:
| Quote: | I have used a home made device, along the lines of Fred's description,
to do exactly what you are asking. The device tapped off of the rs-485
lines with a cmos inverter and then fed the inverter output to a rs232
driver. Jumpers were used to select one or two inversions as
necessary. using two of the devices, and a program I haven't been able
to locate (though I wish I could - it was called something along the
lines of datascope or pals), I could monitor both the recieve and
transmit channels simultaneously.
I would imagine that there are commercially available tools available
for this purpose, but I have no idea how much they would cost, but
probably a lot. You could probably make up your own circuit easilly
enough, but then you would still need to find a monitoring program.
|
i have always used my olg greenleaf VC.EXE program to see side-by-side
output from my sniffer hardware.
greenleaf is alive and well at:
www.gleaf.com
chris |
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Jim
Guest
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| Posted:
Thu Dec 01, 2005 1:15 am Post subject:
Re: Monitoring RS485 |
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| Quote: | http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=8730881991&rd=1&ssp...
this is very cheaper but i'm not sure that is what i need.
Some one can see this item or know what this item do?
|
This is an RS485 - RS232 signal converter. It converts the signal levels
only. That is, the differential RS485 signals are 'converted' to RS232
levels. If you can match the baud rate, number of data bits, stop bits etc.
between a PC and the RS485 comms then you should see a stream of data if
using hyperterminal.
I use devices exactly the same as these to log RS485 data on a small RS485
network. I know the protocol used though and this is essential to
understanding what's going on.
Jim
www.picmodules.com |
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Daniele
Guest
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| Posted:
Thu Dec 01, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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I think that's a big trouble, i don't know how this device work. I have
a keyboard connected with a device and i need to see what message are
exchanged from this two. But i see only that the two device use rs485
to comunicate. Do you think this is an impossible mission? Some help
for me?
Daniele |
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Jim
Guest
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| Posted:
Fri Dec 02, 2005 12:30 am Post subject:
Re: Monitoring RS485 |
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"Daniele" <daniele.gadaleta@gmail.com> wrote in message
news:1133437674.119447.229060@g44g2000cwa.googlegroups.com...
| Quote: | I think that's a big trouble, i don't know how this device work. I have
a keyboard connected with a device and i need to see what message are
exchanged from this two. But i see only that the two device use rs485
to comunicate. Do you think this is an impossible mission? Some help
for me?
Daniele
|
To help further,
1) Do you mean that the keyboard is communicating with this 'device' using
RS485 signal levels?
2) Do you know this because you have opened up the case and looked at the
driver chip?
3) Have you monitored the data using a scope?
4) What is the 'device'?
5) Do you know if data is only on the bus when a key is pressed or is data
always apparent (when no keys are pressed)?
In this area nothing is impossible. If its genuine RS485 signal levels and
uses a reasonble protocol (8 or 9 data bits, start & stop bits etc.), then
it could be very easy to capture the data.
What you do with that data is probably the hard part. If all you need is to
see what data is sent on a keypress on the keyboard then this sounds easy...
it all depends.
It's hard not seeing the two devices and not knowing what you are after
exactly, to say easy or hard. But generally getting the data is easy.
Working out what the data does etc. is hard and sometimes VERY hard. If lots
of continuous random looking data and/or data is encrypted in some way then
I wouldn't even bother. But you won't know that unless you have a first stab
at it. Get a scope on the job first. If you can capture a burst of data from
a keypress and your scope has deep memory then you can decipher small
packets by measuring the bits (I hate doing this as it takes ages, but in
your case it would be a start)
....
Jim
.. |
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Daniele
Guest
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| Posted:
Fri Dec 02, 2005 4:24 pm Post subject:
Re: Monitoring RS485 |
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Ok, i opened the box that contains the device, the Keybord isn't only a
keyboard but contains a display and some output device, the
comunication, I think, is full duplex.
1) The keybord is used to setting configuration parameter, the lcd
display and other led's to output the configuration and state
2) No, the driver chip isn't visible, is covered.
3) No, but this is a good idea
4) The device contains a microprocessor or microcontroller, but all the
Integrated Circuit is covered and serial number erased.
5) The data is bidirectional mode from the First device to the second
and return. My plan is to generate an output from the main device to
the keybord and display. Then press a key and see what data is
exchanged. Then i think to generate all the possible output to build
the tree of command and signal.
When I opened the main device I saw printed on board where the keyboard
is connected "RS485" with connections named "A, B , +, -". Only 4 wire.
Jim, thank you for help
Daniele |
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Daniele
Guest
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| Posted:
Fri Dec 02, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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No, but this isn't a quiz like "what type of device is?" :) . The
device is a central for fire alarm. |
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Noone
Guest
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| Posted:
Fri Dec 02, 2005 5:15 pm Post subject:
Re: Monitoring RS485 |
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Daniele wrote:
| Quote: | Ok, i opened the box that contains the device, the Keybord isn't only a
keyboard but contains a display and some output device, the
comunication, I think, is full duplex.
1) The keybord is used to setting configuration parameter, the lcd
display and other led's to output the configuration and state
2) No, the driver chip isn't visible, is covered.
3) No, but this is a good idea
4) The device contains a microprocessor or microcontroller, but all the
Integrated Circuit is covered and serial number erased.
5) The data is bidirectional mode from the First device to the second
and return. My plan is to generate an output from the main device to
the keybord and display. Then press a key and see what data is
exchanged. Then i think to generate all the possible output to build
the tree of command and signal.
When I opened the main device I saw printed on board where the keyboard
is connected "RS485" with connections named "A, B , +, -". Only 4 wire.
Jim, thank you for help
Daniele
|
Is this a keyboard for a Point of Sale device? |
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Jim
Guest
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| Posted:
Sat Dec 03, 2005 12:26 am Post subject:
Re: Monitoring RS485 |
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"Daniele" <daniele.gadaleta@gmail.com> wrote in message
news:1133536090.330205.134250@g47g2000cwa.googlegroups.com...
| Quote: | No, but this isn't a quiz like "what type of device is?" :) . The
device is a central for fire alarm.
|
Do you mean the main control panel device for a fire panel?. What
manufacture and model number is it? I only ask because I have a college who
used to work for a fire panel manufacturer. He might be able to shed some
light on the subject.
From your answers to my long query list it can almost be assumed that the
(lets call it an FP for now), FP microcontroller is controlling the RS485
bus. Therefore it would also be reasonable assumption that it is using a
standard UART and therefore that the data will be able to be picked out
using PC software (Although standard PC UARTS do not support 9-bit data it
is possible in most cases to use the parity bit for the 9th bit, unless the
protocol is using parity as well - lets assume that this is not the case).
So...
My suggestion would be to get hold of one of those RS485 to RS232
converters. Hook it up to a PC serial port and connect the RS485 end to the
bus. You will not need to transmit onto the bus and so this should be quite
easy. Next, scope the waveform on the bus and determine the baud rate and
bit depth, stop bits etc. Then set these parameters in hyperminal and see
what data you capture. Unfortunately because hyperterminal is not a binary
to ASCII converter you will only see ASCII valid charaters and its possbile
that some data will be lost. Once you have this working then you need to
find/beg/borrow/write etc. an application that allows you to capture binary
data (0-255) and be able to display the digits 0-255. If you know VB or VC++
or whatever then this is quite easy using the MSCOM control and in fact if
you got to the "code project" website (www.codeproject.com) you might find
someone has already done one (not checked so I don't know if this is the
case).
Then... start deciphering..
Good luck!
Jim
www.picmodules.com |
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