Monitoring RS485

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

Reply to
Daniele
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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.

Reply to
Fred

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.

Reply to
Noway2

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

Reply to
Anton Erasmus

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

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. Best site on RS485 I've ever found.

Good luck Jim

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Reply to
Jim

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

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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

Reply to
Daniele

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:

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chris

Reply to
chris
[...]

Comlite32 is a free tool from

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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.
Reply to
Dave Hansen

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

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Reply to
Jim

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

Reply to
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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Reply to
Jim

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

Reply to
Daniele

Is this a keyboard for a Point of Sale device?

Reply to
Noone

No, but this isn't a quiz like "what type of device is?" :) . The device is a central for fire alarm.

Reply to
Daniele

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

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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

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Reply to
Jim

hello,

I thinking of realizing a wireless link, from a portable PIC system to a PC. The needed datarate is about 100 kbit. No (or maybe very slow) data from PC to PIC.

Another requirement is to use as much standard components as possible.

So there seems 2 ways to go: wifi or bluetooth.

Now my guess is that bluetooth devices are easier to interface with a pic, and more general available (in small quantities) then wifi.

Anyone has experience with these interfaces ? Any other comment ?

thanks, Stef Mientki

Reply to
Stef Mientki

Or just use a reasonable terminal emulator. For Windows based PCs Realterm come to mind but there are others. FOr that matter it was possible to do this with PC-Kermit if I remember correctly. Hyperterminal is worth rather less than you paid for it.

Robert

Reply to
R Adsett

Well, after some day of work i have this trouble:

- I don't know what is the speed of the device

- I don't know how many bit it ues

- I don't know if parity bit is present

Then when I connect the PC with the two device, the display of second device (the keyboard, with lcd display) send a connection error (open the connection via Hyperterminal). What my problem? How i can decide what is the configuration parameters for Hyperterminal (speed, data bit number, parity, stop bit number, ecc...)? It's linked with integrate type? I can read the IC's part number than I can search for spech?

Thanks in advanced Daniele

Reply to
Daniele

With an oscilloscope, you can tell the speed within seconds.

If single bytes are sent with delays between, see above.

See above.

Hyperterminal is crap. When you open a com port with data present, hyperterm says it cannot open the port in 95% of the cases. This is a hyperterminal error. Use for instance TeraTerm (free), which works like a charm. With TT you can also change all com settings (baud, bits etc) on the fly without having to close the connection first, like hyperterm wants.

Drop hyperterm and use decent software.

Meindert

Reply to
Meindert Sprang

What software? can you give me some one?

Reply to
Daniele

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