dll calling issue

[bulebell]

when i use the NIDAQ.dll，in the labview .it can run and show it data ,but if i call this dll,the result is null ,what's wrong？

NIDAQ_070528.zip

test_dll.vi

[candidus]

The configuration of the Call Library Function Node is wrong. Take a look at the header file of your DLL. The required function prototype is:

void __stdcall NIDAQ_Wave_Get_070528(char DAQPort[], double rate,

long samplesPerChannel, long inputTerminalConfiguration, LVBoolean *Result,

double *Amplitude, double *Frequency, char ErrorMsg[], long *len);

Your Call Library Function Node is actually configured for:

int32_t __stdcall NIDAQ_Wave_Get_070528(void *input terminal configuration, int32_t Amplitude,

int32_t Frequency, CStr DAQ Port, int32_t samples per channel, int32_t rate);

[bulebell]

The configuration of the Call Library Function Node is wrong. Take a look at the header file of your DLL. The required function prototype is:

void __stdcall NIDAQ_Wave_Get_070528(char DAQPort[], double rate,

long samplesPerChannel, long inputTerminalConfiguration, LVBoolean *Result,

double *Amplitude, double *Frequency, char ErrorMsg[], long *len);

Your Call Library Function Node is actually configured for:

int32_t __stdcall NIDAQ_Wave_Get_070528(void *input terminal configuration, int32_t Amplitude,

int32_t Frequency, CStr DAQ Port, int32_t samples per channel, int32_t rate);

thanks very much！ can you help me to offer me a sample? i am a freshman.

[candidus]

You have to configure the Call Library Function Node according to the prototype of your C function, all argument types and positions have to match.

Here is a modified version of your VI with the (hopefully) correctly configured Call Library Function Node:

test_dll.vi

Note: A function argument that returns data must be a pointer. If an argument returns a string you have to allocate memory before: You can initialize an array of U8 and use that as string argument.

[bulebell]

You have to configure the Call Library Function Node according to the prototype of your C function, all argument types and positions have to match.

Here is a modified version of your VI with the (hopefully) correctly configured Call Library Function Node:

test_dll.vi

Note: A function argument that returns data must be a pointer. If an argument returns a string you have to allocate memory before: You can initialize an array of U8 and use that as string argument.

thanks very much. for your information, i had wrriten a successful program.