Dear NI forum members,
I'm trying to connect a power meter of Siemens (slave) to PC (master), eventually read out power values from LV. I use Modbus RTU for the communication between the master and the slave. The device has RS-485 output, and I use a Siemens-verified RS-485 to RS-232 converter. The problem is that the serial port (COM3, this is a real serial port) remains busy and unreachable after one successful operation at the beginning. When this problem appears once, I can communicate with the device neither via NI-MAX nor a Modbus communicator software (Simply Modbus 8.0.6 and the vendor's own software Siemens Parametrization Software). I cannot find out what is causing this blockage despite all my trials. The different things (or various combinations of them) I did for solving this problem:
- Making sure the connection configurations are correct (baud rate, parity etc..)
- Closing the VISA session with a VI
- Resetting the device and the PC
- Making sure that there is no other program using the serial port (vendor's own software, another open/running VI, firewall). I also checked from the Procexp by searching for "Serial", and nothing appears.
- Change the setting at: LabView Tools->Options->Environment->Automatically Close VISA sessions to make sure all VISA sessions are closed
- Tried with another serial port (virtual and non virtual)
- Tried with another PC
- Reinstalled all the drivers
- Changed the LabView from 2011 to 2016
- Bought a new PCIe card with two real COM ports (by hoping that they have more buffer and won't get "choked" by data coming from an unidentified mysterious serial source)
- Went from Windows 7 to 10
The problem did not appear only once when I made a completey new system. Afterwards same thing happened. I cannot perform a loopback test via NI-MAX. NI-MAX recognizes the device but cannot communicate (see picture 1). The log of the NI-I/O Trace is at the Picture 2.
I'd be very happy and thankful to hear any of your comments,
Kind regards,
Kaya