>>Message imported from previous forum - Category:Trio Data Radios<<
User: joelw, originally posted: 2018-10-17 22:26:06 Id:117
This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.
I'm trying to set up communications between two Allen-Bradley SLC 5/04 PLCs with two QR450 radios using the DF1 Half Duplex protocol, but I can't get it to work correctly..! Currently both radios are on my test bench and the RF is connected into dummy loads, so I don't think the RF side is the problem.
I've put a protocol analyzer at the remote end and I can see the end of the message is being cut off, the radios at each end are set with no flow control on the serial ports, and I'm not sure what timing settings are required for this type of application? Can anyone suggest what settings I should use to transmit 50 'N' registers from one PLC to another with QR450 set for No flow control on the serial port?_**
Perhaps give it a try with just wires... and without the flow control wires (you might need to put the loopback in place, shorting DTR to DSR etc)
If this doesn't work, then I doubt you'd have a chance doing it with the radio either.
A suggested troubleshooting checklist to follow:
- As suggested by Bevan, make sure your PLC's are talking successfully in a hard-wired mode.
- Prove the radios are working by running TView Diagnostics from one and polling the other repeatedly. Ensure you have decent receive signal level & VSWR.
- Configure the serial ports of the radios (you are using serial DF1 I presume? Not sure there's an Ethernet type?) Serial Device Server mode should work very well in both radios. Eg RS-232, No Handshaking, Standard packet layer, Master radio is TCP Client and Remote is TCP Server, match the IP addresses and IP port numbers.
- Pass a little simple serial data (eg text) from one to the other eg with Hyperterminal or PuTTY or whatever your favorite simple program is. Make sure the radios are passing data.
- Only now connect the two PLC's via the radios. Watch the serial port LED activity to see if there may be an mis-wiring issues.
If at any point you have troubles, contact our Tech Support team at 1-888-226-6876 or by email at SupportTRSS[at]schneider-electric.com. They are going to want to see radio config files, serial cable pinouts, and a description of how the PLC ports are configured.
Thanks guys for the advice,
I tried the hardwire connection between the two PLC's without radios as you suggested, and as I expected it all worked fine with no issues. Unfortunately I'm working to some tight deadlines and the equipment has now been shipped to site for installation before the Easter break, so I'm now dependent on our contractor to get everything working!
While the kit was in the workshop I did check the radios out, and they were configured for; Serial Device Server mode RS-232, No Handshaking, Standard packet layer, Master radio TCP Client, Remote TCP Server, and the IP addresses and IP port numbers were all matched.
I tried a Hyperterminal session at each end through Serial port 1 on each of the QR450's and I could pass messages back and forth okay between each end. It looks like the Standard packet layer mode doesn't allow enough time for the PLC messages to pass-through, as longer messages are being truncated, so it looks like it could be a timing issue?
Not sure about Custom mode and the configuration, is this worth trying?_**
Have not had time to get any Allen-Bradley gear out onto the bench. But if your messages are being truncated the first thing I would try is the Modbus packet layer setting. It sounds like it's only for Modbus, but really what it does is set up a buffer so any messages are sent in one continuous stream. Standard mode may send messages in smaller chunks.
As always, if you are having any time-sensitive issues the SCADA Forum is not the right place to solve them. I notice that I'm a month late - I only get on the Forum intermittently! In such cases please contact our Tech Support team: