Wait/Pause function?

[thecakeisalie]

While working out some of the kinks in our code, i stumbled upon a problem. That problem being that I could not have the robot wait for a certain period of time before continuing with its code. So now my question is this: Is there any function that can be used to pause the robot for a certain amount of time?
Thanks.

[Ether]

Originally Posted by thecakeisalie

While working out some of the kinks in our code, i stumbled upon a problem. That problem being that I could not have the robot wait for a certain period of time before continuing with its code. So now my question is this: Is there any function that can be used to pause the robot for a certain amount of time?

When you say "I could not have the robot wait for a certain period of time before continuing with its code" did you mean precisely that, or did you mean when you tried to do it, the robot would stop responding to driver commands while it was waiting?

[thecakeisalie]

I tried to do it with a simple for loop:
for (int x= 0; x< 500; x++)
this was made in autonomous periodic, which I believed would count up one every 20 miliseconds, which should equal around 5 seconds. But this did not work and did not delay the robot at all.

[rbmj]

You can try Wait(double) in Timer.h

And that's just a simple two instruction loop. It won't occupy the processor for long (though it will waste computing power when compared to a yield AFAIK), it won't be reliable (timing could change very easily based on process scheduling), and it may be optimized out by the compiler.

[thecakeisalie]

Originally Posted by rbmj

You can try Wait(double) in Timer.h

And that's just a simple two instruction loop. It won't occupy the processor for long (though it will waste computing power when compared to a yield AFAIK), it won't be reliable (timing could change very easily based on process scheduling), and it may be optimized out by the compiler.

Thanks, I shall try your suggestion.

[Jay Meldrum]

Something like this maybe useful for pausing. This example is directed towards auton, but can be applied in any instance of pausing

m_autoPeriodicLoops++;
//Make sure in your init you set m_autonomousCase = 1;
switch(m_autonomousCase)
{
case 1:
{
    //Reset auto counter
    m_autoPeriodicLoops = 0;
    m_autonomousCase = 2;
}
case 2:
{
     if(m_autoPeriodicLoops < 50)
     {
         //Wait for 50 loops 50 * ~20ms = ~1 second
         robotDrive->TankDrive(0.0 , 0.0);
     }
     else
     {
         //Robot will drive after the 50 loops have completed
         robotDrive->TankDrive(0.5 , 0.5);
      }
}

This will pause the robot for about one second (this can vary depending on how much other code is running, and what you have your Periodic loop set to refresh at). Default is about 20 ms.

By using this method you can have other things in the background running in your loops but you are not "stopping" the cRio completely by using a Wait function.

[Travis Hoffman]

We use a timer to implement delays. Here is our bread and butter 2-ball front of key autonomous code - this is called from AutonomousPeriodic:

void XM15::AutoThree1(void)
{
	//printf("3-PT 1 - Front of Key\n");
	
	#define	TH1_READYDWELL	4.0		//Dwell time to permit to move to shot position
	#define TH1_SHOTDELAY	0.5		//Short pause between oktoshoot signal and feeding ball
	#define	TH1_SHOT1DWELL	0.4		//0.5 OK - Feed time for first ball
	#define TH1_SHOT2DWELL	1.0		//Feed time for second ball
	#define	TH1_REGENDWELL	1.5		//Wait for shooter to regain speed = originally 2.0
	
	switch (autonStep)
	{
		case 1: //Select Front Key Three Arm Position & Spin Up Shooter 
		{

			autofrontkeythree_sw = 1;
			
			shooterstate = ON;
			
			if (delaytimer->Get() < delayset) 	//Wait until the timer times past the preset delay
			{

				//Waiting...
				
			}
			else
			{
				delaytimer->Stop();
				
				autotimer->Reset();
				
				autonStep = 2;			
			}	
			
			break;
		}
		case 2: //Wait for arm and shooter to be ready (or watchdog timeout), then fire a ball 
		{				
			
			if ( (oktoshoot == 1) || (autotimer->Get() > TH1_READYDWELL) )
			{	
				autotimer->Reset();

				autonStep = 3;
			}
		
			break;
		}
		case 3: //Wait for a short moment after arm in position before firing a ball
		{				
			
			if (autotimer->Get() > TH1_SHOTDELAY) 
			{
				autocagefeed_sw = 1;
				
				autotimer->Reset();

				autonStep = 4;
			}
		
			break;
		}			
		case 4: //Stop firing after timeout
		{
			if (autotimer->Get() > TH1_SHOT1DWELL)
			{
				autocagefeed_sw = 0;
				
				autotimer->Reset();
				
				autonStep = 5;
				//autonStep = 7;		//Debug - permits tuning of initial shot timing
			}
						
			break;
		}
		case 5: //Wait for shooter to regain speed, then fire again 
		{			
			if (autotimer->Get() > TH1_REGENDWELL)
			{
				if (speedok == 1)
				{

					autocagefeed_sw = 1;
					
					autotimer->Reset();
					
					autonStep = 6;
					
				}
			
			}
			
			break;
		}
		case 6: //Turn shooter off after 2nd ball is fired
		{		
			if (autotimer->Get() > TH1_SHOT2DWELL)
			{
				autocagefeed_sw = 0;
				
				autotimer->Reset();
				
				autonStep = 7;
			}
								
			break;
		}	
		case 7: //Program is done - turn off the shooter, place arm in load position
		{
			
			shooterstate = OFF;
			
			//autofrontkeythree_sw = 0;
			
			//autoloadball_sw = 1;
		
			break;
		}
		
	}
	
}

[adein]

I use a state system and a Timer object inside of an 'iterable' function. The function returns false until the operation is complete. This works well if you use the 'Iterable' robot template that comes with WindRiver.

The state variable 'state_' must be set to kPhase1 before the function is called the first time (make sure you don't keep setting the state to kPhase1 each time through the control loop). The timer will have a resolution equal to the duration of the calling control loop.

bool TechnoJays::SomeFunction() {
	double time_left = 0.0;
	// Get the timer value since the last event
	double elapsed_time = timer_->Get();

	switch (state_) {
	// Start the timer and move to phase 2
	case kPhase1:
		timer_->Stop();
		timer_->Reset();
		timer_->Start();
		elapsed_time = timer_->Get();
		state_ = kPhase2;
		// Fall through into kPhase2
	// Do nothing until the time has elapsed
	case kPhase2:
		// Calculate time left
		time_left = delay_time_ - elapsed_time;
		// If enough time has passed, continue
		if (time_left <= 0.0) {
			timer_->Stop();
			state_ = kPhase3;
			// Fall through to kPhase3
		} else {
			break;
		}
	// The time delay is finished, continue on
	case kPhase3:
		// Return true indicating that the function is complete
		state_ = kNotRunning;
		return true;
	default:
		state_ = kNotRunning;
		return true;
	}

	return false;
}

[enrique]

Originally Posted by thecakeisalie

While working out some of the kinks in our code, i stumbled upon a problem. That problem being that I could not have the robot wait for a certain period of time before continuing with its code. So now my question is this: Is there any function that can be used to pause the robot for a certain amount of time?
Thanks.

Wait(1.0);