TestStand sequence error handling

Question

I have a sequence which calls DLL steps and subsequencies (which also call DLL steps). I would like to know which is the best way to handle DLL error return values. My DLL's return non-zero values on error and also error message string.
I have configured all my DLL steps as Actions. In the "Post Action" of each DLL step I have set a custom condition: "If Locals.status != 0 Goto destination (end_ERROR)". In each of my sequence I have end_ERROR and end_OK labels at the end. In the end_ERROR block I store the DLL numeric error code and error string to StationGlobal variables (StationGlobals.system_error and StationGlobals.error_msg), which I then display in the Cleanup Group of my main sequence, if StationGlobals.system_error != 0.
My prob
lem is basically this: How can I tell the end user the DLL step name which returned error code, and also tell in which sequence the error occurred. Currently I only get error codes and strings from DLL's but there will be so many DLL calls, so knowing the exact location would be usefull.
I am not sure whether this is the most pratical way to do this. Are there any built-in mechanisms in TestStand to do this? Should I change my DLL steps to Pass/Fail Tests? There seems to be TestStand property RunState/PreviousStep? Maybe I could somehow use this in my end_ERROR label to check where the error occurred.
Any help would be greatly appreciated.
BR,
Timo Sakari

Answer 1

I'm not sure of the prototype of your dll functions as far as how the error code and message are returned, but there is an easier solution that involves the use of built-in properties of the action steptype.
When you are "specifying the module" of a DLL Flexible Prototype Adapter step, you can specify that the return value or any output parameter (those passed by reference) can be assigned to the Step.Result.Error.Code property value. You can also specify that if this value falls within a predetermined range it will cause the Step.Result.Error.Occurred boolean value to be set to true. If this property is set to true, the specific step will be marked as causing an error in the report and the error message will be reported to the user as it happens. If you want to
see examples (including DLL source code examples) that are structured to more efficiently use these properties, take a look at the examples C-DLL based examples in the \Examples\AccessingPropertiesAndVariables.
For more information on using the DLL Flexible Prototype Adapter (more specifically the parameter settings mentioned above), take a look at Chapter 13 of the TestStand User Manual (available via the Sequence Editor's Help menu).
Jason F.
Applications Engineering
National Instruments
www.ni.com/ask