Siemens MPI Communication

Hi masters,

I have some issues in MPI communication between Proface HMI and S7-300. I'm using a MPI adapter which is same like SSW, one side is MPI and the other side is RS-232.

It talks between the two devices, but the problem is the read time is too long, normally it takes about 4-8 seconds to get the status from PLC. I checked the status online in PLC, when a P.B. is pressed, the PLC got it immidiately as well as the status change, but the HMI will get the signal after 4-8 seconds delay.

Is there anyone know where the problem is and how to solve that?

Thanks

in this case... you should be limited by rs232 speed... but still enough for transmitting few data, maybe you could post more info?

- whats speed on MPI side?
- whats speed on rs232 side?
- how many data is going through at once?
- what is the VARIABLE refreshing 'cycle speed' ?
- what exactly is your adapter ? is it the 'gateway' ?
- idle only then transmitting from PLC to HMI or vice versa as well ?

marius said:

in this case... you should be limited by rs232 speed... but still enough for transmitting few data, maybe you could post more info?

- whats speed on MPI side?
- whats speed on rs232 side?
- how many data is going through at once?
- what is the VARIABLE refreshing 'cycle speed' ?
- what exactly is your adapter ? is it the 'gateway' ?
- idle only then transmitting from PLC to HMI or vice versa as well ?

Click to expand...

Thanks.

Speed: MPI side 187.5k, RS-232 side 115.2k
Other settings:
Retry Count:2
Parity Bit: Odd (Not selectable)
Stop Bit: 1 (Not selectable)
Data Length: 8 (Not selectable)
Rcv. Time Out: 8 Sec
Tx Wait time: 0 mSec

Data amount: about 800 variables include some DInts

All the status of toggle P.B. is set to high scan rate, most variables set to low scan rate, the others (about 50) set to middle scan rate [not sure if that's the 'cycle speed']

The adapter is made by Proface, the part number is GP070-MPI-41, I don't know if it is a gateway, it transfer the MPI physical carrier from MPI to RS-232, but in HMI side, the addressing is still siemens format, like DBxxx.DBWxxx or DBxxx.DBXxxx.x and I, Q, M address as well.

The problem is more like transmitting from PLC to HMI only.

By the way, I trid different RS-232 Speed settings, all are the same delay time from 19.2 to 115.2k.

well... i don't know adapter personally, i just looked into manual and there is manufacturers advice to use maximal possible speed of your adapter... so this should not be the problem (unless adapter somehow malfunctious)

i have this idea: have a look in Hardware Config or NetPro and create an MPI connection of CPU to another station ... by default there are no connections in project - so there may not be enough communication resources ?

Is this a new application ? Do you have any previous experience with HMI programming ?

If this is an application with only the Proface HMI connected to the PLC, then I think that douyi is in the right track, that you should try to limit the communication load.
Try to cut down on unnecessary tags.
Try to group tags together in the same memory area (in stead of many segmented memory areas).
Increase the update time of tags that dont necessarily need to be updated frequently.

JesperMP said:

<snip>
Try to cut down on unnecessary tags.
Try to group tags together in the same memory area (in stead of many segmented memory areas).
<snip>

Click to expand...

Sometime a big help is to send all boolean data (bits) as integer or DINT reducing the overhead on the comunications load.

This is most easily done by manipulating boolean data in the screen by referring to word.bit in addressing and on the PLC side to make use easier you may wish to move the "Words" to Bits to use in the rest of the program for clarity. I usually put all these moves in a seperate subroutine for organization.

Acutally, I'm limited by Pro-face software. I'm writing all the bits to Dint, but on the HMI side, I can only read bit, so I have to access 32 times for one DINT (if they have seperate status information). I can't recall there are any HMI software can read a value (16 or 32 bits) and transfer to seperated bits, maybe I'm wrong, but with Pro-face i cannot.

I'll try to creat another MPI node in HW config. Meanwhile, I'm going to try Siemens adapter instead of 3rd party product.

douyi said:

Acutally, I'm limited by Pro-face software. I'm writing all the bits to Dint, but on the HMI side, I can only read bit, so I have to access 32 times for one DINT (if they have seperate status information). I can't recall there are any HMI software can read a value (16 or 32 bits) and transfer to seperated bits, maybe I'm wrong, but with Pro-face i cannot.

I'll try to creat another MPI node in HW config. Meanwhile, I'm going to try Siemens adapter instead of 3rd party product.

Click to expand...

Are you using GPP-Pro or Pro Designer? With GPP-Pro I can access the 2nd bit in byte 53 on a S7-200 by asigning the button etc. to V532 where the last digit is the bit number. Not sure how this works on a 300. I think similar things can be done with Pro Designer.

I found the reason which cause slow response, it's too much trafic, too much variables passing by.

Seems I have to find the way to read faster from HMI, I'm thinking of upgrade from MPI to Siemens TCP/IP. Is that better or fairly the same?

Thanks everyone.

douyi said:

I found the reason which cause slow response, it's too much trafic, too much variables passing by.

Click to expand...

If a screen "only" has 20-30 variables to display, then it could work even with a serial MPI adapter.
I dont know Proface, but I can imagine that you could optimise the communication if only the data that is shown on a screen is requested from the PLC.
On other HMI vendors system it works in the way that data are only polled when needed, unless the programmer specify to poll it constantly.

I doubt that a Siemens serial MPI adapter will do any difference.

An ethernet CP could be the solution, but it is a bit expensive.

JesperMP said:

...I doubt that a Siemens serial MPI adapter will do any difference.

An ethernet CP could be the solution, but it is a bit expensive.

Click to expand...

I tested out Siemens Serial MPI adapter yesterday and it's not compatible with Pro-face HMI.

I'm going to test Ethernet CP tomorrow to see the difference.

It seems like in Pro-face HMI all the variables need to be updated, the update rate can only choose from Fast, Medium and Slow.

douyi said:

I tested out Siemens Serial MPI adapter yesterday and it's not compatible with Pro-face HMI.

Click to expand...

I often use a little ST-402 with s7-200 and I order the MPI interface version.