wincc中的程序：
float a=0;
ptAIVoltageInExp.DasChan = 0;
ptAIVoltageInExp.DasGain = 0; //电压输出范围0-5v 0
ptAIVoltageInExp.ExpChan = 0;
ptAIVoltageInExp.voltage = (FLOAT far *)&a;


if ((ErrCde = DRV_AIVoltageInExp(m_Devhwnd,
(LPT_AIVoltageInExp)&ptAIVoltageInExp)) != 0)
{
DRV_GetErrorMessage(ErrCde,(LPSTR)szErrMsg);

DRV_DeviceClose((LONG far *)&m_Devhwnd);
return 0;
}
printf("aaaaa=%f\r\n",a);