Hi all,
I need help to use LabVIEW 8.20 and shared variables to communicate with a software emulated Allen Bradley SLC500 PLC through RSLinx OPC Server.
I use RSLinx Gateway 2.42, RSLogix 500 7.1 and RSLogix Emulate 500 4.0 on a PC running Windows XP Pro SP2.
My application requires to write and read data from an AB's PLC using a LabVIEW VI as an HMI (Human Machine Interface) application.
Using the interactive procedure I successfully create the OPC client instance as well all the input and output shared variables; also I am able to bind them to the right PLC registers using the browsing capabilities of the LabVIEW shared variables engine.
However, the problem is that I am only able to write from LabVIEW to the the PLC's internal registers; when I attempt to configure and use a variable to read or to read/write from any PLC register the shared variable engine always returns an error -1950679030 (Unspecified error) from the function ni_tagger_lv_read.
Placing a shared variable indicator/control on the front panel the small connection marker becomes green only when the variable is configured as write only; if I configure the variable as read only or as read/write, the connection marker is always red.
It is also strange to observe that also the write operations return an error code -1950679030, but the operation completes successfully (the affected PLC registers are correctly modified!); to avoid that these errors cause the VI to show a blocking dialog box on the screen I am forced to attach an error indicator to the error out terminal of the variable.
Can anyone help me to solve this strange problem?
Please note that I am interested in using shared variables to solve my problem because I am interested to use also logging and alarming capabilities of the LabVIEW shared variables engine; I cannot consider the use of DataSocket functions because they don't grant those functionalities.
Thanks in advance for any suggestion.
Message Edited by frada on 10-26-2007 05:46 AM
