counting incoming pulses (parallel port)

Question

I'm still beginner and trying to count incoming pulses (square wave) via pin 10 (S6) of parallel port. Frequency input is 1Hz-100Hz. No pulses are when the logic is HI, and I start counting as soon as its logic is LOW.

I did something like this:

int y = 126; // HI logic

do
          {
                y = PortAccess.Input(889);
                textBox1.Text = Convert.ToString(y);

                textBox1.Refresh();


           } while ((y == 126) || (y == 62) );   //126 is HI level, 62 is LOW

and i detect and count the changes of HI and LOW in a textbox:

private void textBox1_TextChanged(object sender, EventArgs e)
        {

            count = count + 1;

            textBox3.Text = Convert.ToString(count);

            textBox3.Refresh();

        }

with this code i count the pulses twice the input frequency
however the wait loop (do while) will make the application frozen if I switch to another application.

Any suggestion here? I'm trying to do a multithreading but cant figure out how and whether it's the correct solution.

I also tried to sample the incoming signal (square wave) with a timer (1ms -30ms interval), but it cant count correctly (count too slow most of the time). Am I coding it correctly?

     private void timer1_Tick(object sender, EventArgs e)
        {
            y = PortAccess.Input(889);
            if (y == 126)
            {
                textBox1.Text = Convert.ToString(y);

            }

            else if (y == 62)
            {
                textBox1.Text = Convert.ToString(y);

Can someone help me with better algorithm?

thx a lot

Mike Hankey · Answer

Check out the Application.Idle event handler. This handler will be called when your CPU is idling so that it other processes will not be affected. Secondly when you set the text in a TextBox you do not need to refresh it as you are doing! Good luck hope this helps! Mike

ray · Answer

I tried Application.Idle but it counts too slow than its real frequency... private void Form1_Idle(object sender System.EventArgs e) { y = PortAccess.Input(889); textBox1.Text = Convert.ToString(y); } private void textBox1_TextChanged(object sender EventArgs e) { if (textBox1.Text == 62) { count = count + 1; } textBox3.Text = Convert.ToString(count); textBox3.Refresh(); } private void btnStart_Click(object sender EventArgs e) { Application.Idle += new EventHandler(Form1_Idle); }// end method i wonder why (do while) loop makes the program not responsive.

ray · Answer

Thanks Mike i'll try to create a separate thread. the idea as to why i need to update the textbox in real time is because i want to display something like a distance counter or gas pump counter :)

Mike Gold · Answer

since it is difficult for the eye to see anyway at this frequency you can certainly do the pulse counting in a separate thread and throttle the display once a second(using a timer event handler) update the textbox with the latest count. Thread _oThread; MyForm() { _oThread= new Thread(new ThreadStart(CountPulses)); _oThread.Start(); } int _pulseCount = 0; void CountPulses() { while () { _pulseCount = } } // timer event handler timer_tick { textBox1.Text = _pulseCount.ToString(); } }