Can not connect to PLC when third node (HMI) is added to the MPI bus
Status: Beta
Brought to you by:
lettoz
Menu
▾
▴
2 Attachments
#12 Can not connect to PLC when third node (HMI) is added to the MPI bus
Hello,
I use the Prozess-Informatik 9352-USB MPI-USB interface, PLCVCOM, and libnodave to connect to a PLC. This works as long as the MPI-Interface and the PLC are the only devices on the bus (output of testMPI -d in attached file libnodave0.8.4.4-mpi-no-hmi.txt). But when the HMI is also connected to the same MPI bus, daveConnectPLC() fails with timeout (libnodave0.8.4.4-mpi-with-hmi.txt). Communication between PLC and HMI works however (or so I'm told, I'm not on site).
daveProtoMPI2 behaves the same way, daveProtoMPI3 successfully completes initialisation, but later _daveGetResponseMPI3 fails with -10 (with or without HMI). I also tried libnodave 0.8.5: No difference.
The PLC is a S7 313C, the HMI is Provicom MT-50.
This is the first time we use MPI (always used WinAC RTX before), so I might miss something obvious.
best regards
turned out that this is not really a software issue:
1) they changed the power supply of some component (``change USB power supply to S7 power supply''---um, yeah)
-> connection worked when PC was connected to the Profibus after HMI and PLC were running
2) the PC must not use MPI address 0 (PLC has address 2, HMI as address 7)
-> connection worked also when starting the machines with all parts connected
3) then, initialisation still failed some times, which was fixed by replacing the MPI-USB interface with what seems to be a less defective one.
To summarise: Don't stay on MPI address 0, then blame the hardware.
Good thing that no one wasted time on this :-)