S7 MPI issues after CPU upgrade

[chopin]

Hello guys,

I have upgraded the old 318-2aj00-0ab0 cpu to a 317-1ak14-0ab0. After an upgrade there seems to be a communication issue to a HMI panel (6av6 542-0ca10-0ax0)

The connection is over MPI. With the new CPU I have BF1 LED flashing occasionally, once per 30-60 seconds.

On the HMI the displayed values are flashing (for 2 seconds it will display values, for another two ######).

There is absolutely nothing in the diagnostic buffer apart from PLC stop/start/warm restart action after the changeover.

After the cpu change I have changed the communication settings in the HMI project to point to 317 rather than 318 and downloaded the project.

HMI is running WinCC Flexible 2008SP5 application.

I have compared my old and new projects in terms of MPI addresses/baud rates but it is all exactly the same. There has been no change to the PLC program as well. Old and new blocks are identical.

Can someone advice where else to look at.

 

[JesperMP]

The BF flashing occasionally points to that there are intermittent problems on the network. As long as they do not affect anything else but the HMI communications, it wont trigger entries in the diagnostic buffer.
It could be that the problem is just coincidental with the change of the CPU, or it has to do with handling of the cable and/or connectors.
I would look at the usual suspects:
Cable damage, connector defective, shield not properly connected to a ground busbar, missing equipotential connection for distributed panels, network speed and distance outside spec, noise generators near the devices and/or cables ....

What is the baudrate and the distance ? How many other devices on the MPI network ?

 

[chopin]

If I put the old CPU back the comms are healthy.

The distance to the HMI is about 4-5meters.

The baudrate is 187.5Kbps

 

[JesperMP]

Do you have a messageview on the HMI to display system messages ?
The HMI should generate some system messages that could be helpful.

Does any of the PLCs or the HMI have the setting "only master on the bus" ?
If so, turn it off.

 

[chopin]

Does any of the PLCs or the HMI have the setting "only master on the bus" ?

Would that be somewhere in the hardware config? I cannot see anything similar.

I can't see any message view on the HMI. I assume there is tick box I need to turn on somewhere in the project and re-download. Is that right?

At the moment I am remaking the plug on PLC side.

 

[JesperMP]

The only master on the bus is in the hardware config of the interface of the various devices.

For the messageview, you have to either add a messageview to the standard template so that it appears on any screen.
Or make a special screen with a message view where you can see logged system messages.
Definitely a must-have on any HMI.

 

[chopin]

Thanks Jesper, much appreciate your input.

I managed to solve the problem. It is stupid but what it was is I mimicked the MPI configuration from the old project. In the old one in the HW MPI was shown as not networked. I had the same in new PLC. As I switched it to Networked it started working.

 

[JesperMP]

Good that you got it working. But to me it doesnt explian the BF flashing.