Import dll callback function

[johnnyLabVIEWlongtime]

Having trouble with this line "void   (*m_callback)(_t_pciCommand *cmd);" in PciApi.h file. I have replaced it with NULL and was able to import 2 functions, PciAllocCommand and PciSendCommand. I was then able to get valid information using GetValueByPointer.VI, but crash most of the time.

typedef struct _t_pciCommand

{

                t_pciCommandType                      m_command;

                t_commandError                          m_error;

                long                                               m_gpVal;

                void                                                (*m_callback)(_t_pciCommand *cmd);

                long                                              m_param[MAX_PCI_PARAMS];

                int                                               m_state;

                int                                               m_retries;

                int                                               m_expected;           

                long                                            m_origParam[MAX_PCI_PARAMS];

} t_pciCommand;

All files attached. Based on this callback funtion, I can't seem to resolve 2 functions, called PciAllocCommand and PciSendCommand.

Thanks,

John

[rolfk · Accepted solution]

LabVIEW can't support callbacks through Call Library Nodes. You will need to write a wrapper DLL in C/C++ that translates the callback function into a LabVIEW user event. Search for PostLVUserEvent here and on LAVA to find discussions and examples about this.

Beware: some sound C programming knowledge will be definitely required to understand this stuff and adapt it to your use case.

[johnnyLabVIEWlongtime]

Rolf, I kind of expected this answer after going through this forum. My C skills are not that strong but I can modify exsisting code. I would like to take a different approach by removing the callback from the exsisting code. The callback function isn't required so I replaced it with NULL in the DLL.

What I need help with is to properly configure the VI. Using the references you pointed out in other posts, I was able to modify what Labview generated, but would like some verification that it is done properly.

[rolfk]

Feel free to upload a VI and the description and C prototype of the function and its datatypes. I'll have a look at them then.

[johnnyLabVIEWlongtime]

The manual is "pci_api_manual_jb.doc", The funtion I care most about is PciAllocCommand and the #1 issue I have is how to pass "m_param[0]" , "m_param[1]" and "m_param[2]" to the dll. The original h file is "PciApp(original).h" . The second issue would be if removing the callback functionality I need a VI to poll the status of "t_PciCommand "Function without writing to it.

For example, PciAllocCommand(c_baudrate, NULL, 0). How do I set baud = m_param[0]?

Also I am adding a TestApp.exe example of what I want to do in Labview, focusing on the Param1 and Param2

[johnnyLabVIEWlongtime]

Up to rev 9 with better results and no crashing. I believe the remaining issue is how to poll "t_pciCommand".