Frontline NetDecoder on DH+ with U2DHP box

[andy_1983]

Hi,

I wondered if anyone has any experience using the Frontline net decoder software on DH+ with the U2DHP box?

I'm running into a couple of problems, and Frontline have said its a Rockwell problem - I do have a Tech Connect account but thought I'd try here first, as suspect Tech Connect will just refer me to Frontline.

So one issue is you have to shut down RSLinx - which is fine, but then I don't seem to be able to change the node number of the U2DHP from the NetDecoder software. Any one come up with a way of changing it from node 0 without using Linx?

The second issue, and this is the one that's tripping me up, is that the NetDecoder software seems unstable on the network dropping node 0 (itself) on and off line all the time. the comms between PLCs and SCADA keeps going, but when you look at the events list in net decoder you just see appearing and then dropping a few mS later.

I've tried to run this on three separate laptops and two different sites.

Anyone got any tips or found it equally unsuitable? Rockwell actually recommend using this software with their product.


Thanks

Andy

 

[blendo75]

The U2DHP must have its' node address set by RSLinx. This shouldn't be an issue for Frontline because RSLinx doesnt have to be continuously running for the node address to remain with the U2DHP.

This should work:

1. Start with U2DHP disconnected.
2. Set up the driver in RSLinx with your desired node address.
3. Plug in the U2DHP. Node address will be set.
4. Shut down RSLinx.

The U2DHP should retain the node address after RSLinx shuts down.

 

[Ken Roach]

May I ask what might sound like a foolish question: Why does the U2DHP need a node number at all ?

If it has a node number, then it has to participate in DH+ token passing (at a minimum) and transmit onto the network itself. That seems to me to be the opposite of what a network analyzer and protocol decoder should be doing.

I have used NetDecoder with Modbus and DF1 and DeviceNet and EtherNet/IP but never with DH+. I skimmed the user manuals but didn't see anywhere that it described setting a node number for the U2DHP.

 

[andy_1983]

The U2DHP must have its' node address set by RSLinx. This shouldn't be an issue for Frontline because RSLinx doesnt have to be continuously running for the node address to remain with the U2DHP.

This should work:

1. Start with U2DHP disconnected.
2. Set up the driver in RSLinx with your desired node address.
3. Plug in the U2DHP. Node address will be set.
4. Shut down RSLinx.

The U2DHP should retain the node address after RSLinx shuts down.

That sounds like a good plan - I’ll try that and see what happens.

 

[andy_1983]

May I ask what might sound like a foolish question: Why does the U2DHP need a node number at all ?

If it has a node number, then it has to participate in DH+ token passing (at a minimum) and transmit onto the network itself. That seems to me to be the opposite of what a network analyzer and protocol decoder should be doing.

I have used NetDecoder with Modbus and DF1 and DeviceNet and EtherNet/IP but never with DH+. I skimmed the user manuals but didn't see anywhere that it described setting a node number for the U2DHP.

Hi Ken,

I agree with you, I’d have thought it should be passive and just sit monitoring traffic without participating in the token passing. When it’s running though node zero is dropping in and out all the time - when you look at the log that net decoder produces, it’s just a long list along lines of

Node 0 dropped off bus
Node 0 had missing or truncated field in frame
Node 0 reappeared
Node 0 token/solicit/command/reply sent but not by token holder
Node 0 dropped off bus

I also checked manual and it never mentions setting a node - which again implied it should be passive.

……..

I asked Frontline tech support for advice, this was their reply:

The RS-232 and RS-422/485 analyzers from Frontline are considered passive, but I don't believe the U2DHP interface from RAB is.
In their configuration documentation, it mentions setting the station number else the default is 0.
Apologies for any inconvenience, I would recommend referring to Rockwell technical support for further assistance on this specific adapter since we do not manufacture/sell it.
Our software (NetDecoder) is just acting as one method of logging from this hardware

Andy

 

[Ken Roach]

That's a surprisingly low effort answer from FTE. They are an "Encompass Partner" that shares technology with RA, and according to both FTE and the RA Knowledgebase, firmware version 1.7 of the U2DHP (newest is 1.8) has features specifically to work with NetDecoder.

The Quick Start Guide doesn't specifically mention the U2DHP, but it does point you to a possible source of specifics:

> All documentation is found in the ‘Desktop / Frontline NetDecoder [version] / Documentation’ folder

My recollection is that the U2DHP has only the round mini-DIN8 style connector, so it's meant to plug in at a PLC-5 or DHIO or SLC-5/04 port. How do you have it connected ?

And are you certain there isn't a Node 00 on the network already ?

 

[andy_1983]

My recollection is that the U2DHP has only the round mini-DIN8 style connector, so it's meant to plug in at a PLC-5 or DHIO or SLC-5/04 port. How do you have it connected ?

And are you certain there isn't a Node 00 on the network already ?

It’s a network with 4x SLC 5/04 (node 1 to 4) and one SCADA connected as node 77. I plugged it into the mini-DIN8 on one of the SLCs.

I wondered if there was actually a defaulted node on the network, as that would appear as node 0, but I can’t find it if there is and all PLCs are in one building, so I’m thinking it’s unlikely.

I’ve had a look through the NetDecider help files in the application but there was no further information.

My U2DHP box was made in December 2017 and has FRN 1.007

 

[andy_1983]

I’ve done sone more experimenting.

I’ve set up a network on my bench with two PLCs (5/04s) sending DH+ messages to each other. One as node 1 the other as node 7. Both PLCs are running happily .

Test 1 - Run net decoder with the U2DHP box connected (last time it was used was set to node 0 by Linx). Everything working fine, I get no errors unless I unplug and reconnect the DH+ line between PLCs then obviously it starts to play up.

Test 2 - Run U2DHP box in linx and set node up as 7 - power on and off a couple of times, linx confirms box is 7….. I then shut linx down and run net decoder, again everything is fine. Either U2DHP had defaulted back to node 0 or it’s passive on the network and not part of the token passing.

Test 3 - use linx to reset the U2DHP back to node 0. Then change PLC that was NODE 1 to be NODE 0 and make node 7 read from 0 rather than 1. Run net decoder, so now I have a PLC that’s node 0 and U2DHP that’s node 0…. Result = all good, net decoder saying NODE 0 and 7 healthy - again U2DHP must be passive


So - from all this I’ve come to the conclusion that despite what Frontline said, the U2DHP is indeed passive.

And more importantly I’m now wondering what’s going on at site. I clearly have something that’s node 0 on the network - either it could be a defaulted device like an HMI or maybe some old comms unit I don’t know about. Or else could it be one of the PLCs is randomly changing itself to node 0 then recovering it’s real identity - never seen that before…. Ideas welcome.

Andy

 

[JTCat]

And more importantly I’m now wondering what’s going on at site. I clearly have something that’s node 0 on the network - either it could be a defaulted device like an HMI or maybe some old comms unit I don’t know about. Or else could it be one of the PLCs is randomly changing itself to node 0 then recovering it’s real identity - never seen that before…. Ideas welcome.

Andy

RSLinx should be able to find it if does indeed exist on your DH+ Network