Search the Community

Hello all, I encountered quite a puzzling problem. May be some of you know a solution or some trick. Shortly As a rule, Invoke Node works asynchronously. If two Invoke Nodes are called in different loops, threads, or processes, they are executed independently. But it does not happen if they are used to execute some function of an ActiveX (OCX file). I need to invoke the same function of an ActiveX asynchronously. Of course, I create two instances of the ActiveX but, the Invoke Node that is called first blocks execution of the second; i.e. two invocations are executed consequently. I need a “pure-asynchronous” execution but could not find any solution. Some interesting experiments Experiment 1. I created an ActiveX containing only one function. The function simply waits for a number of milliseconds than returns a String value. If called from a non-LabVIEW program, two instances of the ActiveX work asynchronously without any problem. But it is not so in LabVIEW Experiment 2. To do a “pure” experiment, I created two independent ActiveX-es. Both have the same function but even names are different. This block diagram shows the same test but with two different ActiveX-es (the same code as in Experiment 1 but the ActiveX holders point to two different ActiveX-es): Two Invoke Nodes are not executed asynchronously. They wait for each other. Experiment 3. This experiment is probably most puzzling. I created a sub-VI that do exactly the same – waits for a number of seconds. Of course, if such a sub-VI is reentrant, its instances can be invoked asynchronously. Now I tested what happens at parallel use of Invoke Node on instance of the ActiveX and on the sub-VI: Now - the show! If the sub-VI is invoked first (bottom structure), the ActiveX is invoked asynchronously. But! If the ActiveX is invoked first, invocation of the sub-VI waits! Thanks in advance for all ideas.