How to change the state of line by using the DAQmx api in delphi

[pnh]

Hi,

The product I using is NI-USB-6229.

Currently I am developing my own application to connect to the machine by using delphi, I get the API from http://digital.ni.com/public.nsf/allkb/A6715AA42405ACD786256F0A00633B8F.

My problem is with the digital I/O. I would like to set the state of the lines to "high". Following is my code:

ErrorMsg:=DAQmxCreateTask('task',@TaskHandle);

ErrorMsg:=DAQmxCreateDOChan(TaskHandle,'Dev1/port0/line8','a',DAQmx_Val_ChanForAllLines);

ErrorMsg:=DAQmxSetDOLineStatesStartState(Taskhandle,'Dev1/port0/line8',10192); 

ErrorMsg:=DAQmxStartTask(TaskHandle); 

However, the program failed at the 3rd line, I catch the error msg by using this function:

DAQmxGetExtendedErrorInfo(errorstr,194);

It return me following error message:

Measurements:Specified property is not supported by the device or it is not applicable to the task.

Property:DAQmx_DO_LineState

Channel Name:a

Task Name:task 

StatusCode:-200452

What I want to do is just same like the "Digital I/O" tab of "test panels" in "Measurements & Automation".

I want to change the direction of the line(input or output) and the state of the line (high or low) then start it.

I not sure what going wrong with my code or my coding direction is totally wrong?

At the time being, I would like to mention that, it is functioning perfectly in Measurements & Automation tool.

I highly appreciate your help.Thank you. 

[Meadow]

Hi Pnh,

In the program that you do, you were creating a DO task and then you set up a start up states of the particular line. It is not the right function to use to set a digital data as in the test panel in MAX.

You probably would like to take a look at the example code on how to do simple digital signal generation as copied below.

 /*********************************************/
 // DAQmx Configure Code
 /*********************************************/
 DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
 DAQmxErrChk (DAQmxCreateDOChan(taskHandle,"Dev1/port0","",DAQmx_Val_ChanForAllLines));

 /*********************************************/
 // DAQmx Start Code
 /*********************************************/
 DAQmxErrChk (DAQmxStartTask(taskHandle));

 /*********************************************/
 // DAQmx Write Code
 /*********************************************/
 DAQmxErrChk (DAQmxWriteDigitalU32(taskHandle,1,1,10.0,DAQmx_Val_GroupByChannel,&data,&written,NULL));
 if( taskHandle!=0 ) {
  /*********************************************/
  // DAQmx Stop Code
  /*********************************************/
  DAQmxStopTask(taskHandle);
  DAQmxClearTask(taskHandle);

I hope that this explanation helps.

[marles]

Hello! Can anyone tell me what is DAQmxSetDOLineStatesStartState used for? I would like to configure a NI-PCI-6723 board so that its digital I/O ports to be outputs and with the '0' logic on each digital line when the board is powered up. By default, I see that the lines are in '1' at startup and this bothers me! Can I change this so the lines startup with '0'? I'm wondering if the function "DAQmxSetDOLineStatesStartState" helps me with my task. Can anyone please help me with this problem?