continuous data acquisition from parallel port in Java

For one of my projects, that is related to nerve conduction study, I need to acquire data continuously from a parallel printer port in Windows XP. The analogue data is processed by an Analogue to Digital converter and then serve it to parallel printer port. 开发者_如何学PythonTo get familiar with the data acquisition process I was trying to acquire data from a frequency signal generator that is connected to ADC and the frequency is set to 50 Hz. So far I have been able to read the data from PC using Java, but I'm worried that I'm making mistake somewhere.

The problem with the acquired data is, say for example, if I take first 500 data and plot it then I get a wave form but its not smooth enough indicating that the data is missing or scattered someway. I am giving a screenshot of a sample data plotting for 500data here . Hope someone can give me some hints where I am making mistake and show me some guidelines to solve it. Thanks in advance.

Sample code:

for (int i=0; i<500;i++) { 
      lpt.output(0x37a,32); //configures DR for data input by making C5bit of CR high
      lpt.output(0x37a,33); //starts data acquisition process by making C0 bit of CR high
      for(int j=0;j<1000;j++){     } //dummy loop to provide some time delay for ADC output to Stabilize
      arr[i] = lpt.input(0x378); // reading and storing the data in an array
      for(int k=0;k<10000;k++){} // dummy delay loop to provide sample data interval
}