S7300 cpu314c-2dp and mp270b using profibus dp

Hi

I am trying to setup a PROFIBUS DP connection between a Siemens S7-314C-2DP plc and a Siemens Multipanel MP270B. The PLC and touch panel are the only two things on the profibus DP network so i got a profibus cable made up with the terminating ends (with looping resistor or something like that)

I´m using SIMATIC Manager to create the project, i have configured the Hardware, and the Network using Netpro, in the SIMATIC Manager. I´m connected the CPU with the PC using an MPI interface and it works good,there is no problem with that. The problem is with my PROFIBUS DP Subnet, i have configured it and when i save and compile it, the SIMATIC doesn´t show me any errors. Then i load all the project to the PLC,but when i try to send data to the PLC using a button in the MP270B there is no change in the output.

I have configured the DP port of the PLC using the PLC as a Master and i have unchecked the option "Only master in the bus" in the WinCC connection configuration, so i suppose in that way i am using MP270B as slave.

I was wondering if also to to this, i need to load the SFC´s Function Blocks corresponding to DP Profibus (SFC12,SFC13,SFC58-59,etc) in my S7-300 program. Is this necessary when i am tryng to establish connection with a MP270B using Profibus DP?...or Are the functions only used in Profibus DP communication between PLC´s?

I have never done a profibus connection before and i am wondering, If i am right or what settings do i need to set in order for the two devices to communicate over profibus DP ?

Thanks for any help, and i am sorry for my profibus "newbie" type question.

Tom Van der Krotmann

Hi Tom.

First of all, I recommend that you have a STEP7 project with both 314C-2DP and MP270 panel.
In the HW Config of both 314C-2DP and MP270, set them to be connected to the same Profibus network.
When you configure the PLC connection in WinCC Flexible, you simply select the 314C-2DP as the target.
This procedure automatically takes care of the various settings you would otherwise have to select manually.

For your information, communication between a HMI panel and the CPU is master-master, not master-slave.
You do not have to program any SFC to exchange data with the panel.
The panel takes care of retrieving the data from the CPU.

Are you sure you have the cabling right ?
If you use Profibus connectors, be sure that the cable goes into where the arrow points INTO the connector, and this at both CPU and panel.

Thanks

Hello Jesper,

First, thank you for your quick answer.
Well, in fact i have started to think that i have a hardware problem. And it seems that all it´s pointing to my cable as you said. The cable that i am using was made by myself, with its respective pin connections, It is a copper cable using sub d9 connectors with the next configuration:

PIN NO.
1 Not used
2 Not used
3 RxD/TxD-P
4 CNTR-P
5 DGND
6 VP
7 Not used
8 RxD/TxD-N
9 Not used
Case Shield

This is the same in both extremes of the cable, i have already switched the IF1B port in the MP270B into RTS on pin 4 (
DIP Switches: 4=on,3=off,2=off,1=off)
After that i wonder i f my cable is right or if i need to use a commercial standard cable, manufactured by SIEMENS for Profibus DP. Or if i need to build it with a special Type of cable, for example Type A.
I will appreciate any suggestion or advice very much.
:site:

for cable wiring
simply connect 3 to 3 and 8 to 8 and 5 to 5 .its over, nothing more..may be shield...thats it
add the hmi device to the profibus network in netpro.
if you have not integrated the wincc flexible project with step-7 ,make sure you select the same baud rate,and node address in wincc flexible as in netpro and hw config.

Thanks

Well i have made it in that way, but i am using a tin-plated copper multipaired cable conductor with shield (Aluminum/Mylar Foil with Drain Wire),and with a PVC jacket, and normal D9 connectors putting 3 network ending resistors between:

--390Ohms-- --220Ohms-- --390Ohms--
/ \/ \/ \
PIN6 PIN3 PIN8 PIN5

My doubt is if it should work in that way or if i necessarily need to use the SIMATIC NET, LAN CABLE FOR PROFIBUS TWO-WIRE, SHIELDED (Part No.6XV1830-0AN20) and the Bus Connectors (Part.No.6GK1 500-0EA02), instead of the materials that i am using.

If it is not a standard Profibus cable, then try with 187.5k. At this speed almost anything goes. But dont connect anything to pin 4 ! Like falgunsave says, the important pins are 3 and 8, and 5 for the shield.
To check if the error is with the cable you can also swap your homemade cable for a profibus or MPI cable.
If you get it to work this way, you can continue testing your application.

I am not sure about the DIP switches. You mean those that are on the back of the panel ? I dont think the combination you suggested is the right one. I dont remember the combination, but there is a small diagram on the back of the panel.

If there is a question about the Profibus cable, why not use it to go online or download between your PC and the PLC. Unless I am missing something, it does not matter if it is a Profibus cable; use it to communicate with the MPI port on your PLC. If it works under, you know your cable is good.
One thing that I noticed with the MPs, I have an easier time getting communications between the PLC and MP if in the S7-Transfer Settings I leave the protocol highlighted that I want to use. So when I want to use Profibus, in the MP WinCE Control Panel, I would leave Profibus (not MPI) highlighted when I close the S7-Transfer Settings applet. Of course the address, transmission rate, and highest station need to be set here as has been previously mentioned.

Hello Guys!

First..sorry because I couldn´t answer quickly... I finally found the problem, It was not in hardware. It was in the way that i am refering to my inputs/outputs. In this case i just only needed to use Mark Registers (i.e. M0.0 , M0.1, for mapping my Inputs/Outputs). At the beginning i was mapping my I/O refered directly to my physical I/O (i.e. E124.0,E124.1) and in that way i found that it didn´t work so i was wrong.
But thanks... some advices that you gave to me were useful for Profibus newbies like me.
Now I want to add more devices to my Profibus network, and i want to make it using cables and connectors made by myself. I am wondering if i can do this in that way or Do i need to buy commercial connectors. The topology for my network will be in a daisy-chain array.
I will appreciate any help or advice, very much...

Greetings .... Tom Van Der Krotmann

You can make your own connectors. But if you use standard Profibus cable (with a single strand in each wire) you will find that soldering a connector is not easy so that the result will last. Is it worth the effort ?

Anyway, it is ethernet everywhere from now on, so I would dive into that rather than fiddling too much with Profibus. I am not saying that Profibus is on the way out, but you will find ethenet everywhere you look.

I found profibus connectors technical datasheet, and i see that the derivation line to further field devices and stations takes only two lines (for transmission RxD/TxD-P and RxD/TxD-N)so i suppose that if i am using a homemade cable, it´s enough if i weld the pair of cables and use them like an extension. And well i suppose to that i just have to put termination resistors in the connector of the last device at the end of my network.

I have in an emergency have had to solder a profibus cable in standard DSUB connector. The problem is that the single strand wire in a standard profibus isnt suited for soldering, even if it seems to solder all right. The soldered single-strand wire will be sensitive to the slightest mechanical force. So dont trust is to last. And if you cannot trust it, why bother ?
PLCs, operator panels, and the processes they control are not cheap, does the effort pay off, is the risk bearable ?

All right Jesper. Thank you very much for your help again man... I will follow that recommendations... They make me think about it... and may be i won´t do it like i have considered...