I do not see yet a reply with the magic trick. Maybe I have to elaborate on my question.
Commonly, my application defines the digital I/O port for four input lines and four output lines. This is done by creating a DAQmx task for input, creating four digital input lines, and starting this task. The same is done for an output task. (The port name in the code below will be Dev1).
/* clean up old tasks */
NIDAQPC_CleanUpGlobalTask();
DAQmxErrChk (DAQmxCreateTask("",&NIDAQPC_TaskHandleInput));
for (i = 0; i < NIDAQPC_CONFIG_LINENUMBERINPUT; i++)
{
sprintf(LineName, "%s/line%0d", NIDAQPC_Devices[Device].DigitalPortName, i);
DAQmxCreateDIChan (NIDAQPC_TaskHandleInput, LineName, "", DAQmx_Val_ChanPerLine);
}
DAQmxErrChk (DAQmxStartTask(NIDAQPC_TaskHandleInput));
DAQmxErrChk (DAQmxCreateTask("",&NIDAQPC_TaskHandleOutput));
for (i = NIDAQPC_CONFIG_LINENUMBERINPUT; i < NIDAQPC_CONFIG_LINENUMBERINPUT + NIDAQPC_CONFIG_LINENUMBEROUTPUT; i++)
{
sprintf(LineName, "%s/line%0d", NIDAQPC_Devices[Device].DigitalPortName, i);
DAQmxCreateDOChan (NIDAQPC_TaskHandleOutput, LineName, "", DAQmx_Val_ChanPerLine);
}
DAQmxErrChk (DAQmxStartTask(NIDAQPC_TaskHandleOutput));
If my computer restarts and nobody is there to log-on, the state of the digital lines seem undefined. And the shutter that is connected to one of the digital output lines, starts to open and close rapidly.
From the Windows SDK help and from some examples, I found how to make a simple Windows Service. I have installed this service so that it starts automatic after boot. Inside the service, I send a call to my function that defines the input and output tasks. And I stop the service because I do not need it anymore.
void WINAPI ServiceStart (DWORD argc, LPTSTR *argv)
{
HANDLE Events[2] = {NULL, NULL};
if (!ServiceStatusToManager(SERVICE_START_PENDING,NO_ERROR,100)) goto CleanUp;
ServerStopEvent = CreateEvent(NULL,TRUE,FALSE,NULL);
if ( ServerStopEvent == NULL) goto CleanUp;
Events[0] = ServerStopEvent;
if (!ServiceStatusToManager(SERVICE_START_PENDING,NO_ERROR,100)) goto CleanUp;
if (!ServiceStatusToManager(SERVICE_RUNNING,NO_ERROR,0))goto CleanUp;
// End of initialization
////////////////////////////////////////////////////////
// Service is now running, perform work until shutdown
Delay(30.0);
SHUTTER_Init();
SHUTTER_Set(-1L, SHUTTER_Closed);
ServiceStop();
CleanUp:
if (ServerStopEvent) CloseHandle(ServerStopEvent);
}
Without the delay of 30 seconds, the service gets stuck when initializing the digital lines i.e. the call to SHUTTER_Init does not return. I know this because I added print-statements before each function call that gets stored in a log-file. With the delay of 30 seconds in ServiceStart, I get (tested 5 times) successful definition of the ditigal I/O lines without the need to log-on.
I assume that one or multiple of the NI services are needed before I can start a task. Specific I expect that a NI service builds an inventory of all the devices and their names.
I like to know how to check when I can start a task. So my next step was to look which services do exist after 10 seconds delay:
Delay(10.0);
hSCM = OpenSCManager(NULL,NULL,SC_MANAGER_ENUMERATE_SERVICE | SC_MANAGER_CONNECT);
if (hSCM != NULL)
{
EnumServicesStatusEx(hSCM,SC_ENUM_PROCESS_INFO,SERVICE_WIN32,
SERVICE_STATE_ALL,NULL,dwBufSize, &dwBufNeed,&dwNumberOfService,NULL,NULL);
if (dwBufNeed > 0)
{
dwBufSize = dwBufNeed + 0x10;
pBuf = (PUCHAR) malloc(dwBufSize);
if (pBuf != NULL)
{
EnumServicesStatusEx(hSCM,SC_ENUM_PROCESS_INFO,SERVICE_WIN32,
SERVICE_ACTIVE,pBuf,dwBufSize, &dwBufNeed,&dwNumberOfService,NULL, NULL);
pInfo = (LPENUM_SERVICE_STATUS_PROCESS)pBuf;
for (i=0;i<dwNumberOfService;i++)
{
//pInfo[i].lpDisplayName
//pInfo[i].lpServiceName
//pInfo[i].ServiceStatusProcess.dwProcessId
}
free(pBuf);
}
}
CloseServiceHandle(hSCM);
}
The list does include a few NI services. To repeat my original question: can I use the active-status of any of the NI services (with optional a short delay) as an indicator that I can define a DAQmx task before log-on?
Regards, Jos
