Monitoring RS485

Started by Daniele November 29, 2005
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

"Daniele" <daniele.gadaleta@gmail.com> wrote in message 
news:1133261166.326280.232030@g14g2000cwa.googlegroups.com...
> 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.
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.

On 29 Nov 2005 02:46:06 -0800, "Daniele" <daniele.gadaleta@gmail.com>
wrote:

>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
> 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
During my search for a commercial converter I found this one:


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?


Thanks 
Daniele

Noway2 wrote:
> 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
On 30 Nov 2005 06:00:12 -0800 in comp.arch.embedded, "chris"
<cruff@cts.com> wrote:

[...]
>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.
> 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
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