PCIe-6536 with error code -88700

[corcoted]

 Hi, I am using a PCIe-6536 board to upload data from computer to another digital card. And I meet one trouble, which says,

"DAQmx Error: An internal error occurred

Status Code: -88700"

I include codes used here (neglecting variable initializing part), almost everything is in default setting. I am wondering if there is something wrong with the sequence of board initializing.  

Could someone help me out? Thanks a lot in advance.

    DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
    DAQmxErrChk (DAQmxCreateDOChan(taskHandle,DEVPORT,"",DAQmx_Val_ChanForAllLines));
    DAQmxErrChk (DAQmxTaskControl(taskHandle,DAQmx_Val_Task_Commit));
    DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,CLOCKLINE,Rate,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,sample_num));
//   I think error occurs in the below sentence, by adding debug sentence

   DAQmxErrChk (DAQmxWriteDigitalU32(taskHandle,sample_num,FALSE,Timeout,DAQmx_Val_GroupByScanNumber,DataArray,&written,NULL));
    DAQmxErrChk (DAQmxStartTask(taskHandle));    
 
Error:
    if( DAQmxFailed(error) )
        DAQmxGetExtendedErrorInfo(errBuff,2048);
    if( taskHandle!=0 ) {
        DAQmxWaitUntilTaskDone(taskHandle,Timeout);
        DAQmxGetWriteTotalSampPerChanGenerated(taskHandle,&generated);
        printf("%d samples output successfully\n",generated);
        DAQmxStopTask(taskHandle);
        DAQmxClearTask(taskHandle);
    }
    if( DAQmxFailed(error) )
    {
        printf("DAQmx Error: %s\n",errBuff);
        printf("Press ENTER to exit\n");
        getchar();
        exit(2);
    }
    printf("All output complete, Press Enter key to quit\n\n");
    getchar();

[The_Red_Barron]

Howdy corcoted!

Try switching the order of the DAQmxWriteDigitalU32 and DAQmxStartTask functions.  They should be in this order:

DAQmxErrChk(DAQmxStartTask(taskHandle));

DAQmxErrChk(DAQmxWriteDigitalU32(taskHandle,sample_num,FALSE,Timeout,DAQmx_Val_GroupByScanNumber,DataArray,&wri tten,NULL));

Regards,