Modbus data source setup

[JoelHaggar]

You probably need a longer timeout setting if this is going over the internet. I would try up to 5000 ms.

[patd2020]

Thanks for your suggestion Joel but still getting the no response error

[JoelHaggar]

I think you'll need to run a Modbus packet capture software on the end of the virtual com port to verify what communication is or isn't coming out.

The error you are seeing in Mango just means Mango sent out a message and didn't get any response back from the device.

[patd2020]

any recommendations
for this type of software?

[JoelHaggar]

Here is a good free one: http://www.isquared.ca/English/downloads_CC.htm RS-485 spy

[phildunlap]

Hi Patd,

Some other thoughts as I'm also reading...

Is it possible the slave IDs are flipped / mistaken? I see COM1 trying to talk to slave 2, and COM2 trying to talk to slave 1. Sometimes operating systems can switch their identifier on you at a reboot and such.

You can try to make equivalent requests from your test software and Mango through Modbus IP to netcat, then compare (or if you're feeling serial you can cat -v /dev/ttyUSBN)...

[sudo] nc -l 900 > testSoftware
*run query from test software pointed to this machines ip, port 900*
[sudo] nc -l 900 > testMango
*run query from Mango*
hexdump -C testSoftware
hexdump -C testMango

But alas you are probably using Windows with names like "COM1" :P You can do it if you have a Linux system on hand.

[patd2020]

Thanks Joel & Phil. yes I see your point about the non matching slave/com port. I should have matched it to avoid confusion but that is actually how they are setup/ Slave 1 on Com2 and slave2 on COM1. Yes I am on Windows. I will attempt to run your suggested tests and report back

[patd2020]

here is the RS485 Modbus guide for the Flow m0_1466480777062_FlowRS485.doc

[patd2020]

Here is an update. I now can read the registers of both devices. the second device which had Modbsus ASCII as default I had to change to RTU. Now I need to figure out how to set up the data points

[patd2020]

Sorry I meant to say I change the data source to MODBUS IP because I could not get the COM to to work