Using Analog Input and Output at Once

[Heeshung]

I'm trying to get analog input and output working at the same time, namely in MS Visual Studio with C++.  Currently, I've run the Acq-IntClk analog input example, which works, but the voltages are off.  However, the expected voltage drops are still present.  When measuring zero voltage, the output has a tendency to drop ~.1V every two or three elements in the array.  For example, when exposed to no voltage, data[0] will start at -5.9V, and then decrease to -6.0V at around data[2].

Now on to the actual issue:

#include <stdio.h>
#include <math.h>
#include "NIDAQmx.h"

#define DAQmxErrChk(functionCall) if( DAQmxFailed(error=(functionCall)) ) goto Error; else

int main(void)
{
	int         error=0;
	TaskHandle  taskHandle=0;
	TaskHandle	taskHandle2=0;
	TaskHandle	taskHandle3=0;

	int32 read;

	float64     data[4000];
	float64		data2[100];

	char        errBuff[2048]={'\0'};
	int			i=0;
	
	int32   	written;

	for(;i<4000;i++)
		data[i] = 10.0*(double)i/4000.0;

	
	/*********************************************/
	// DAQmx Configure Code
	/*********************************************/
	DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
	DAQmxErrChk (DAQmxCreateTask("",&taskHandle2));
	DAQmxErrChk (DAQmxCreateTask("",&taskHandle3));
	DAQmxErrChk (DAQmxCreateAOVoltageChan(taskHandle,"Dev1/ao0","",-10.0,10.0,DAQmx_Val_Volts,NULL));
	DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"",500,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,4000));
	DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle2,"",10.0,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,100));

	DAQmxErrChk (DAQmxCreateAIVoltageChan(taskHandle2,"Dev1/ai0","",DAQmx_Val_Cfg_Default,0,8,DAQmx_Val_Volts,NULL));

	/*********************************************/
	// DAQmx Write Code
	/*********************************************/
	DAQmxErrChk (DAQmxWriteAnalogF64(taskHandle,4000,0,10.0,DAQmx_Val_GroupByChannel,data,&written,NULL));

	/*********************************************/
	// DAQmx Start Code
	/*********************************************/
	DAQmxErrChk (DAQmxStartTask(taskHandle));
	DAQmxErrChk (DAQmxStartTask(taskHandle2));
	DAQmxErrChk (DAQmxReadAnalogF64(taskHandle2,100,10.0,DAQmx_Val_GroupByChannel,data2,100,&read,NULL));


	/*********************************************/
	// DAQmx Wait Code
	/*********************************************/
	DAQmxErrChk (DAQmxWaitUntilTaskDone(taskHandle,10.0));

Error:
	if( DAQmxFailed(error) )
		DAQmxGetExtendedErrorInfo(errBuff,2048);
	if( taskHandle!=0 ) {
		/*********************************************/
		// DAQmx Stop Code
		/*********************************************/

		DAQmxStopTask(taskHandle);
		DAQmxClearTask(taskHandle);
	}
	if( DAQmxFailed(error) )
		printf("DAQmx Error: %s\n",errBuff);
	printf("End of program, press Enter key to quit\n");

	getchar();
	return 0;
}

This code just integrates my two working parts, the analog in and output, but when I run it, I get Error -200477.

Thanks in advance.