Help with NXC multi threading - Solved!

[haydenstudios]

Hi there. I've been learning NXC, (and having quite a lot of fun I might add) but I have ran into a problem. I have been going back-and-forth between John's book and Daniele's tutorial, and have just finished Chapter 7 of the book, and have begun chapter VI of the tutorial. I have copied the example for multi threading shown in the tutorial:

Code: Select all

mutex moveMutex;
task move_square()
{
while (true)
{
Acquire(moveMutex);
OnFwd(OUT_AC, 75); Wait(1000);
OnRev(OUT_C, 75); Wait(500);
Release(moveMutex);
}
}
task check_sensors()
{
while (true)
{
if (SENSOR_1 == 1)
{
Acquire(moveMutex);
OnRev(OUT_AC, 75); Wait(500);
OnFwd(OUT_A, 75); Wait(500);
Release(moveMutex);
}
}
}
task main()
{
Precedes(move_square, check_sensors);
SetSensorTouch(IN_1);
}
The

So that worked, then I decided to make my own program with multi threading which would have the main thread make the motor attached to port A move forward until the touch sensor is pressed, then move backward until it is released, and put that into a loop. The secondary thread would make an image move back-and-forth accross the screen. But for some reason, when I run the program, only the main thread runs. I might add that I received no compilation errors. When I remove the main thread and change the secondary to the main thread, it works fine, so I know theres no problem with the commands of the secondary thread. So my question is, what's wrong with this code here?

Code: Select all

int NUM;
mutex secondary;

task tray()
{
 NUM = 0;
 while(true){
  Acquire(secondary);
  do{
   ClearScreen();
   GraphicOut(NUM, 0, "Tray.ric");
   NUM += 1;
   Wait(30);
   }
   while(NUM <= 76)
  do{
   ClearScreen();
   GraphicOut(NUM, 0, "Tray.ric"); // If you help me out, just substitute your own image.
   NUM -= 1;
   Wait(30);
   }
   while(NUM >= 0)
  Release(secondary);
 }
}

task main()
{
 Precedes(tray);
 SetSensorTouch(IN_1);
 while(true)
 {
  OnFwd(OUT_A, 75);
  until(SENSOR_1);
  OnRev(OUT_A, 75);
  until(!SENSOR_1);
 }
}

P.S. I'm new to NXC, so feel free to advise me on a few habbits I appear no to be into with certain commands, or which techniques you think would be better for me to be used to using if there are any.

Thanks in advance.

[muntoo]

Your task tray() never starts. Precedes() waits for the current task (task main()) to end.

Code: Select all

task a()
{

}

task main()
{
    Precedes(a);

    while(1);

    // start a; // Never happens!
}

Try this:

Code: Select all

task tray()
{    
    while(true)
    {
        for(int x = 0; x <= 76; ++x)
        {
            ClearScreen();
            GraphicOut(x, 0, "Tray.ric");
            Wait(30);
        }

        for(int x = 77; x >= 0; --x)
        {
            ClearScreen();
            GraphicOut(x, 0, "Tray.ric");
            Wait(30);
        }
    }
}


task otherstuff()
{
    while(true)
    {
        OnFwd(OUT_A, 75);

        while(!SENSOR_1)
            Yield();

        OnRev(OUT_A, 75);

        while(SENSOR_1)
            Yield();
    }
}


task main()
{
    Precedes(tray, otherstuff);
    SetSensorTouch(IN_1);
}

P.S. You should indent with a tab or 2-4 spaces (4 is the "standard" convention) for each deeper "nest" into a block.
Also, until(cond); isn't C; it's only there because of NQC. I recommend not using until(). Instead, use while(!(cond));.

[haydenstudios]

It works! Thanks for your help muntoo!