Anyway, can spirit S7 315 MPI port into 2

Dear sirs/madams,

I am briely explain my situation right now.

First of all, I have a S7 315 CPU with just only one port (MPI port). The port is actually using by one of the control panel device and our customer don't allowed us totally unplug the port that because of they still have using the control panel device to control their machine.

The problem for us now is actually, we need to use the port to link with our HMI machine using NetLink (is a MPI to Ethernet convertor). But unlucky there just only one port.

I just wanna to know is it anyway to spirit the S7 315 MPI port into 2 ports ?

Best Regard,
Joshua

Hello Joshua;

MPI uses an RS-485 physical interface; this means it is a multi-drop standard allowing up to 31 units to connect to the bus. If you are using a point-to-point MPI cable to your control panel device presently, replace it with Profibus cable and connectors (ask your Siemens rep or go to the Siemens support website); that way you can easily extend the MPI connection to your new Ethernet converter. You might have to add the new MPI connection in Netpro (the Step7 network configurator) before it is recognized. Make sure all the modules on the MPi network have different MPi addresses.

Hope this helps,
Daniel Chartier

Have some confuis

Dear Daniel Chartier;

So happy to hear that but one thing is I am still very new in Siemens product. I am definely no idea.

I hope to get some advise from you, what is the part I should to use?

I really not understand that how a MPI port can support profibus cable & connector. Can I have some explaination from you also. Thanks a lot.

I just found out that their currently control panel device is using PG Adapter to communicate with the S7 315 CPU. (just want to let you more clear my situation, because I can't affort to buy so many things at the end no use). Thanks.

Best Regard,
Joshua

Hello Joshua;

Look at the following concept, i am sur eit will work. Remember that profibus and MPI share the same RS-485 physical layer, so you can use the same wire and connectors. Using a Profibus connector with a PG socket (a piggy back pass-through connector) you can connect the programming cable's PC Adapter to this socket and continue the bus without problem.


Talk to a siemens' rep if you have any doubts.
Hope this helps,
Daniel Chartier

Hi Joshua.

The 315 is connected to the "Control panel" (HMI PC connected via the serial PC adapter).

The problem is that the PC adapter draws power off the MPI port on the 315.
As far as I know, the NetLink (MPI/Ethernet adapter) ALSO needs to draw power from the same port ! (And I have heard that it draws so much power that it gets HOT).
So there is no easy way to connect both at the same time, despite that MPI allows multiple drops.

Is it not possible to change the HMI PC with the PC adapter to connect via the NetLink also ?
If so, you could attach the NetLink to the 315 and to an Ethernet switch. From the switch you could then connect to many devices, including the HMI PC.

Thanks a lot

Dear sir,

Thanks a lot.

I learn a lot from your side.

Best Regard,
Joshua

Hang on Joshua.

I think that Daniel and I are saying that "it is possible" and "it is NOT possible" to connect the NetLink and the PC adapter at the same time to the same MPI port.
I may be wrong, but maybe not.

Hmmm.. how do we find the truth then ?

edit:
Further explanation why I think it will not work:
It looks like Daniel suggests to use a two-wire MPI/Profibus cable from the connector to the MPI adapter. There is 5V on the MPI port in the 315, but with just the two wires the 5V is not transferred with the MPI/Profibus cable. The NetLink will need the 5V to get powered.

Is there an option for a separate power supply to the NetLink ?

Cannot

Dear Jesper Møller Pedersen,

QUESTION:
Is it not possible to change the HMI PC with the PC adapter to connect via the NetLink also ?

ANSWER:
1. Yes, cannot...... sir, if let say I use mutlidrop concept for my case. Is it possible to connect everything? Do I need to modify the program inside the S7 315 PLC?

2. If I use the suggestion from above (bus connector), is it have any problem?

Best Regard,
Joshua

Hi Joshua.

I have explained why I think that it will not work in the previous post.
If it is possible to supply the NetLink externally (I dont know, but it could be possible, look into the documentation for the NetLink), then it WILL work.

The other option of connecting the HMI PC is probably possible. I think that the NetLink provides a driver that looks like a "virtual PC adapter". In other words, the HMI PC is connected via the Ethernet port but "thinks" that it is connected via the serial port and a PC adapter. Again, look into the documentation for the NetLink.

Anyway, it should not be necassarry to change the proogram.

External Power

Dear Jesper Møller Pedersen,

The Netlink will draw power from the MPI port. Regarding the external power, I don't think so it can be. Because NetLink is a very small thing & inside the NetLink is just a small chipset and a board only.

From the start, I can understand and actually know how to do all the thing. But after you have explain the power issue for me then now I definely have some confuis and don't how to do right now.

Sir, can you make it more clear for me? Because I am really new new guy in Siemens.... Thank you

Best Regard,
Joshua

OK.
The PC adapter needs to draw power from the MPI port on the 315.
The NetLink also needs to draw power from the MPI port on the 315.
The port on the 315 has pins that sends/transmits the data, and pins that supply 5V, the 5V are what the PC adapter and NetLink needs.
Physically, you can only connect one device like a PC adapter or NetLink to the MPI port.
The special connector, that Daniel suggests, allows you to create an MPI network with several nodes. And you can still connect ONE adapter because there is a 9-pin socket on the connector.
However, the 5V is not wired onto the MPI network. There are only two wires in the MPI cable for the data signal. In Daniels diagram the 5V is not forwarded to the NetLink.
I also think that there is a risk of overloading the 5V in the MPI port on the 315 if it was posible to connect several adapters.

I hope that explains the problem. I would look into using the NetLink for the HMI PC.

Ok..thanks

Dear Jesper Møller Pedersen,

I think first of all, I need to make clear everything first...

Is actually, what I need is a solution to solve this problem. I need one more port. Or either use mutlidrop... whatever, I need a solution. Thank you.

Joshua

Provide some more info on what the "Control Panel" HMI PC really is.
What software ?
What hardware ?

Ok

Dear Jesper Møller Pedersen,

Is actually like this, the siemens system was there long time ago already. But without any SCADA there. Suddenly the plant manager ask us to do upgrading for the plant.

So for our scope is actually develop a HMI application using wonderware and link with the siemens S7 315 CPU to get the data back for reporting purpose.
Intial, I think Netlink is easy to use because just plug & play device. After I brought the Netlink, I just released that some of the CPU is just one MPI port and use by other device.

What I mean the "Control panel"? Is actually a small display screen use to control their machine by manually. This display screen will go through a PC Adapter and link with the S7 315 CPU. Then the operator just can control their machine by press the keys on the control panel.

So that why I can't unplug the port. Then I got no idea how to plug in my Netlink convertor. After few hours research, I found out that MPI is a Mutli point Interface protocol, then I am assume that I can make a cable with 2 9 pins ports (one in two out).

Finally, I try and the result is my Netlink and the PC Adapter can draw the power from the 315 CPU. The PC Adapter work with no problem & I try to ping my Netlink, is ok also. But I try to key in some I/O then request the data from the 315 CPU. I get a error message from NetLink. That is "Master not into the logical token ring"....

So after that utill now I got no other idea to do again...

Please give me some solution and let me try it ok... thanks sir


Best Regard,
joshua

To try and help you I need to know what the PC adapter is connected to.
What kind of "small display screen" is it ?

And how did you connect both PC adapter and NetLink at the same time ?
Did you make your own adapter with two 9-pin connectors ?
That could seem to work, however I would check if the current draw of the two adapters doesnt overload the port on the 315. What I have heard is that the NetLink draws so much current that it gets physically warm.