Data Acquisition Toolbox

Example: Writing and Reading Digital Values

This example illustrates how to read and write digital values using a line-configurable subsystem. With line-configurable subsystems, you can transfer values on a line-by-line basis.

You can run this example by typing daqdoc7_1 at the MATLAB command line.

1. Create a device object -- Create the digital I/O object dio for a National Instruments board. The installed adaptors and hardware IDs are found with daqhwinfo.

• dio = digitalio('nidaq',1);
  

2. Add lines -- Add eight output lines from port 0 (line-configurable).

• addline(dio,0:7,'out');
  

3. Read and write values -- Write a value of 13 to the first four lines as a decimal number and as a binary vector, and read back the values.

• data = 13;
  putvalue(dio.Line(1:4),data)
  val1 = getvalue(dio);
  bvdata = dec2binvec(data);
  putvalue(dio.Line(1:4),bvdata)
  val2 = getvalue(dio);
  

1. Write a value of 3 to the last four lines as a decimal number and as a binary vector, and read back the values.

   • data = 3;
     putvalue(dio.Line(5:8),data)
     val3 = getvalue(dio.Line(5:8));
     bvdata = dec2binvec(data,4);
     putvalue(dio.Line(5:8),bvdata)
     val4 = getvalue(dio.Line(5:8));
     

   Read values from the last four lines but switch the most significant bit (MSB) and the least significant bit (LSB).

   • val5 = getvalue(dio.Line(8:-1:5));
     

4. Clean up -- When you no longer need dio, you should remove it from memory and from the MATLAB workspace.

• delete(dio)
  clear dio
  

Reading Digital Values

Generating Timer Events