Host Engineering Forum

General Category => DirectSOFT => Topic started by: alectek on December 13, 2018, 06:32:12 PM

Title: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: alectek on December 13, 2018, 06:32:12 PM
We have a place using DL260 (with an extension rack) and two c-more panels (EA7-12" AND EA9-15"), also a computer (for programming) is in the network too. Every time when I use directsoft 6.2 to connect to the PLC, Both HMIs shows PLC-001 communication timeout. I changed powersupply, comm card (h2-ecom100), 260 cpu, and the 5 port ethernet switch (nothing else is in the network), the problem remains. Once I disconnect plc from directsoft, everything back to normal.

Right now I put an additional comm card in the rack just for directsoft, the other card is for HMIs, and it is working fine.

I am wondering if anyone can explain to me what is the problem. Because we have several systems like this and they don't need the additional comm card.

Thanks for any help.
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: ADC Product Engineer on December 14, 2018, 08:23:39 AM
Your C-more's along with whatever other comms that you have are hitting the PLC too hard.  You need to add a small bit of poll time to the C-more panels.   Setup -> Panel Manager -> Com Port -> DEV001 -> Poll Time
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: alectek on December 14, 2018, 11:59:05 AM
Thank you for the help. It is improved but not solve the problem. I unhooked EA7, and set the timeout time on EA9 to 2 and increase the Poll time up to 200 (tried 5, 10, 50,100, 200). The error still shows, but I can see some of the values on screen is changing, not like before everything was totally frozen. At 200, a few buttons not write to the PLC even directsoft is disconnected. I am doing remote test through remote desktop connection to the computer Lenovo M710a / windows 10.
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: ADC Product Engineer on December 14, 2018, 12:28:31 PM
Do you have anything else using the ECOM100?  Talking to another PLC perhaps?  SCADA system?  Other devices that the PLC is pulling data from?
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: alectek on December 14, 2018, 12:44:36 PM
There is only a datalogger software in the same computer will read Modbus TCP 32 integers every 2 minutes. The datalogger is using for other places and not giving a problem.

The c-more software is able to transfer to the panel when the plc-001 error happens.

On yesterday, the system is standalone, only two HMIs and the PLC and the computer on a switch. Today, the switch is connected to the plant network, and through the plant network, it is connected to the internet. But nothing else should talk with the PLC.
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: franji1 on December 14, 2018, 01:06:17 PM
What is the timeout value of the C-more connection?  I am not sure of how to check that in C-more, but it may be too low.  This is different than the poll rate.  This is the value that tells the C-more when it does sent out a request, how long should the C-more wait for a response before it assumes the other side is dead, causing the C-more to retry/report an error.

DirectSOFT may poll the PLC at very fast rates.  Not sure what your PLC scan time is, but that can affect the overall comm cycle time too.  What is the PLC scan time?

With an ECOM100 card, there is only 1 hose in/out, so it must process all the communications, and one of the PLC's clients may be expecting
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: alectek on December 14, 2018, 01:37:09 PM
Hello franji1,

The C-more timeout value is 1 (100ms) and I tried with 2.

Directsoft scan time is around 55ms, max is 61, min is 53
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: franji1 on December 14, 2018, 01:55:45 PM
With DirectSOFT connected and doing status, change the c-more to 5 (500 ms) and see if the errors go away.

You also want to double-check the timeout of your DirectSOFT connection.  Make sure it is closer to 500ms, not 100ms.

If the errors do go away, that means that the PLC is able to respond, just not at the rate the C-more/DirectSOFT want it to when other clients are also polling.

The 260/ECOM can do 1 to 4 packets per PLC scan based on the complexity of the requests (this is function of the 260 firmware, not the ECOM firmware).  Hence, it may take multiple PLC scans to respond to any 1 request.  With large scan times, that can easily get you beyond 100ms timeout (2 x 55ms).

By having such a "tight" retry timeout, you end up actually perpetuating the problem because DirectSOFT and C-more will retry, even though the PLC is actually processing ALL the requests, putting more comm load on the system.

It's always best to start the timeouts high, then reducing them and figuring out where the "threshold" is, then doubling it for the actual timeout value.  You really do NOT want clients retrying unless it knows for sure the packet was lost (which is rare, but can happen).  Also, a timeout less than 100ms is usually not necessary.

Remember, this is TIMEOUT, NOT POLL RATE.  Typically the POLL RATE is the FASTEST POSSIBLE rate (not actual rate), because a client typically will not start another comm when it has one pending.  So you may want to change your poll rates back to FAST, just to see if the PLC CAN keep up with the new TIMEOUT value.

Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: alectek on December 15, 2018, 06:01:43 PM
Hello franji1,

I tried 1,2,3,4,5 for the timeout, and found that 4, 5 will eliminate the errors.

So I understand that the Polling rate can be 0, the panel will poll as fast as it can; the timeout will depends on the network delay, poor network gives retries and they add traffics, and makes jam the communication more.

One more question on it, if I set no retry (retry=0), will the panel give an error, then still poll in the next turn, or it will stop polling this data?
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: franji1 on December 15, 2018, 07:21:08 PM
Retry=1 is good.

As long as you do not have a data storm scenario (e.g. other devices broadcasting or some bad Master to the PLC that is constantly sending out requests with minimal timeout values), Retry=1 is good.  But if you set the timeout=50ms on your Master device (e.g. DirectSOFT PC or C-more) with a PLC scan time of 55ms and retry of 3, that would be BAD.
Title: Re: Directsoft interfere the communication between EA7/EA9 to DL260
Post by: alectek on December 17, 2018, 10:25:34 AM
Got it.

Thank you!