Maker Pro
Maker Pro

Monitoring RS485

D

Daniele

Jan 1, 1970
0
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
 
D

Deefoo

Jan 1, 1970
0
Daniele said:
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

Yes, but if it is two way communication it may be difficult to figure out
who is sending what.

--DF
 
Daniele said:
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?

Connecting nodes in parallel - yes, this is what RS485 is designed for.

If you want to connect a PC via RS-232 then you need to convert RS485
signal levels to RS232. Since you only want to listen this is simple.
Connect a MAX481 back-to-back with a MAX232, with the MAX481 configured
to permanently recieve and the MAX481's recieve data pin connected
directly to the MAX232 transmit data pin.
 
J

John - KD5YI

Jan 1, 1970
0
Connecting nodes in parallel - yes, this is what RS485 is designed for.

If you want to connect a PC via RS-232 then you need to convert RS485
signal levels to RS232. Since you only want to listen this is simple.
Connect a MAX481 back-to-back with a MAX232, with the MAX481 configured
to permanently recieve and the MAX481's recieve data pin connected
directly to the MAX232 transmit data pin.


Or get RS232/RS485 converters here:

http://www.bb-elec.com/

I'm not affiliated with them in any way.

John
 
K

Ken Taylor

Jan 1, 1970
0
Daniele said:
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
I did exactly this by just plugging a multiport RS485 card into a PC and
using the receives of two different ports to monitor the traffic in either
direction. A quick-and-dirty VB application displayed the results. Still
does, actually..... :)

Ken
 
J

john jardine

Jan 1, 1970
0
Daniele said:
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
Yes.
Had a 9600 baud setup that broke into gibberish after a few characters were
sent down the line.
Quick and cheap solution was to monitor the RS485 wires using the "+" "-"
inputs of a LM393 comparitor.
LM393 and its output resistor both powered from spare data pins on the PC's
LPT1 port.
Data at the LM393 output pin was sampled at variable rates upto 200kHz from
a PowerBasic programme.
Stored data block allowed a storage scope type display of the actual RS485
voltage transitions. Data decoding and fault finding at my leisure.
10 minutes to build the device and a hour to programme the software.
Nowadays we are no longer allowed to do it this way.
regards
john
 
Top