Code/device to detect RS485 acknowledgment

[rikotech8]

hello everyone.
I have a problem that i can't solve without your help.
since I am a beginner to RS485 communication, I decided to refer to you.
Here is my issue:
I have a field with 48 inverters (Siemens - SINVERT PVM17) communicating with each other and one Datalogger via RS485. Since the datalogger doesn't find part of them, I was wondering if I can create a device that can inspect the buss, or the device communication module. Searching into the forum I came across to this: http://www.ccsinfo.com/forum/viewtopic.php?t=49713&highlight=i2c+bus+scanner
unfortunately not for my interface.
So my task is to make sure that the Inverter's RS485 module works.
Any hints would be much appreciated.
_________________
A person who never made a mistake never tried anything new.

[Ttelmah]

RS485, is _only_ a physical signal description. Nothing else. It doesn't cover 'what' is sent at all. You can send SPI over RS485, async serial at any number of different word lengths (including exotica, like 80 bit formats), and then have any number of different protocols using these formats.

You need to know a _lot_ more about the protocol being used, before any sort of diagnostic can be done.

Are you sure you have the bus termination correct?. This is vital for reliable comms, especially when the number of devices rise.

However a key thing leaps out. Do a search on 'Siemens USS'. Which is the protocol used by their kit. My memory is that a single bus on these devices, is limited to 32 devices maximum. One master, and 31 slaves. 48 devices can't be handled by a single bus....

Might explain why there is a problem.

[temtronic]

Mr. T is right again !!
First hit of his google search 'Siemens USS' is the PDF of the specs. A few pages it is says max of 32 devices( 1 master , 31 slaves).

While the original RS-485 transceivers were only designed for 32 units, Maxim came out with a 128 unit transceiver. I know it works well 'in the lab' as I did tests with it years ago.You can get more if you're 'careful' though.

However , like Mr. T says, you'll have to follow the Siemens USS specs.They've limited the bus to the original transceiver specs.

hth
jay

[rikotech8]

Thank you for the fast reply.
The system had been working for years with no problems.
The problem is from nearly 10 days.

The thing is that the master device is (I think) not a Siemense product. The master device is:
http://www.solar-log.com/en/products-solutions/solar-log-1000/overview.html
That handles with 2 loops each with 24 devices.

The problem is as follows:
Yesterday there was 32 inverters in MPP mode, and 16 offline.
Today it is different, 41 MPP, and 7 offline.
Tomorow would be who knows?
That's why, I want to catch the faulty module in the loop.

My plan was to create a device to request each modul into the loop...
I will