NI DO demo

Software controlled digital output

To check it connect digital output(s) to oscilloscope or to card analog input.

program doportlpi;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes,nidaqmx,SysUtils,StrUtils
  { you can add units after this };
var
  DOTaskHandle:TaskHandle;
  data: byte;
  written:longint = 0;
{************Error handling procedure *****************************************
      Example:
   ErrorCheck(DAQmxCreateAIVoltageChan(AITaskHandle,'Dev0/ai0','',DAQmx_Val_RSE,-10.0,10.0,DAQmx_Val_Volts,NIL),AITaskHandle);

  *******************************************************************************}

  procedure ErrorCheck(AError:longint;ATaskHandle:longint);
  var
    errBuffer:array[0..2048] of char;
  begin
     //get error description
     if Aerror<>0 then begin
       DAQmxGetExtendedErrorInfo(@ErrBuffer[0],2048);
       writeln(PChar(@ErrBuffer[0]));
     //stop and cleat task
     if Assigned(@ATaskHandle) then begin
       DAQmxStopTask(ATaskHandle);
       DAQmxClearTask(ATaskHandle);
     end;
     //stop program
     Halt;
    end;
  end;
{*******************MAIN PROGRAM WITH ERROR HANDLING*************************}
begin
  //task create
  ErrorCheck(DAQmxCreateTask('',@DOTaskHandle),DOTaskHandle);
  //digital input port create
  ErrorCheck(DAQmxCreateDOChan(DOTaskHandle,'Dev1/port0','',DAQmx_Val_ChanForAllLines),DOTaskHandle);
  //task start
  //no need to start task
  ErrorCheck(DAQmxStartTask(DOTaskHandle),DOTaskHandle);
  //for 32-bit digital port use DAQmxReadDigitalU32 function
  //set 1 on all lines of digital port
  //change data:=0 to set 0 or use DAQmxResetDevice function to
  data:=0;
  ErrorCheck(DAQmxWriteDigitalU8(DOTaskHandle,1,1,10.0,DAQmx_Val_GroupByChannel,@data,@written,Nil),DOTaskHandle);
  //use DAQmxResetDevice function here to set signal on Low state
  writeln('number of written samples: ',written);
  //stop and clear task
  if DOTaskHandle<>0 then begin
    DAQmxStopTask(DOTaskHandle);
    DAQmxClearTask(DOTaskHandle);
  end;
end.

see more to:

 ttps://wiki.freepascal.org/NI-DAQmx_and_NI-DAQmx_Base_examples