I am confusing "OnFwdReg"

[walduss]

Hi

I am starting with NXC. I have a code but I am confusing, so I have reduced my code to minimun.

I will show ..

Code: Select all

#define SPIN_SPEED  50


// NXT Port aliases
#define WHEELS            OUT_BC
#define LEFT_WHEEL        OUT_B
#define RIGHT_WHEEL       OUT_C

#define CW     1        // clockwise
#define ACW   -1        // anticlockwise

void Spin(short dir)
{
	// Gira hacia el lado de "dir"
	// Usar CW o ACW
	NumOut(0, LCD_LINE4, dir);
	NumOut(0, LCD_LINE5, sign(dir));
/*
	OnFwdReg(LEFT_WHEEL,  -sign(dir)*SPIN_SPEED, OUT_REGMODE_IDLE );
	OnFwdReg(RIGHT_WHEEL, sign(dir)*SPIN_SPEED, OUT_REGMODE_IDLE );
*/

	OnFwdReg(LEFT_WHEEL,  dir*10, OUT_REGMODE_IDLE );
	OnFwdReg(RIGHT_WHEEL, -dir*10, OUT_REGMODE_IDLE );

}


task main()
{
  Spin(CW);
  Wait(3000);
}

this code work fine, but If I change the main task to

Code: Select all

task main()
{
  Spin(ACW);
  Wait(3000);
}

program do nothing !!! For me it is suppose that Wheels run in oposite direction!!!! (Robot should spin oposite than before)

another test ... If I change main task to ...

Code: Select all

task main()
{
  Spin(CW);
  Wait(3000);
  
  Spin(ACW);
  Wait(3000);
}

or ....

Code: Select all

  Spin(ACW);
  Wait(3000);
  
  Spin(CW);
  Wait(3000);

It runs fine too !!!

So why programn dont work when I try to Spin ACW (AnticlockWise) only ????

thanks in advance and sorry for my english!

[walduss]

Hi again,

I have done another test after restart the brick and the computer.

Code: Select all

#define SPIN_SPEED  50


// NXT Port aliases
#define WHEELS            OUT_BC
#define LEFT_WHEEL        OUT_B
#define RIGHT_WHEEL       OUT_C

#define CW     1        // clockwise
#define ACW   -1        // anticlockwise

void Spin(short dir)
{
	// Rotot turn to "dir" direction
	// Use CW o ACW
	
	NumOut(0, LCD_LINE4, dir);
	OnFwdReg(LEFT_WHEEL,  -sign(dir)*SPIN_SPEED, OUT_REGMODE_IDLE );
  TextOut(0, LCD_LINE5, "Left done");
	OnFwdReg(RIGHT_WHEEL, sign(dir)*SPIN_SPEED, OUT_REGMODE_IDLE );
  TextOut(0, LCD_LINE6, "Right done");
}


task main()
{
  Spin(ACW);
  Wait(3000);
}

in this case Numer "-1" is display in line4 and but never it is shown the text "Left done". also the program never end.

But if I call Spin(CW) instead Spin(ACW) in main task, Program run sucessfully.

Anybody have any clue?

[walduss]

After some test I have discover hat the issue is due to "sign" function.


When NXT run "-sign(dir)" where "dir" is ACW the program get an unexpected behaviour (at least for me)

So I have remove sign function (really, it was not necessary)

#define SPIN_SPEED 50


// NXT Port aliases
#define WHEELS OUT_BC
#define LEFT_WHEEL OUT_B
#define RIGHT_WHEEL OUT_C

#define CW 1 // clockwise
#define ACW -1 // anticlockwise

void Spin(short dir)
{
// Gira hacia el lado de "dir"
// Usar CW o ACW

OnFwdReg(LEFT_WHEEL, (dir)*SPIN_SPEED, OUT_REGMODE_SPEED );
OnFwdReg(RIGHT_WHEEL, -(dir)*SPIN_SPEED, OUT_REGMODE_SPEED );
}

task main()
{
Spin(ACW);
Wait(3000);
}

Now, program seem to be fine.

But really I dont know if the issue with -sign(dir) is a bug or not. If anyone could confirm it will be apreciated.

[HaWe]

I agree, OnFwdReg is weird and often produces unexpected behaviours -
(to be honest: just like all of the advanced motor functions ...)
I personally sacrificed all of them.

Better you write your own functions!

[walduss]

I agree, OnFwdReg is weird and often produces unexpected behaviours -
(to be honest: just like all of the advanced motor functions ...)
I personally sacrificed all of them.

Better you write your own functions!

Sorry, I dont understand what you mean with create your own functions?

You mean create in a low level lenguage like NCB?


Now I am having more issues with other secuences of program, so any help will be usefull!

[mattallen37]

If I were you, I would use OnFwd and/or OnRev.

[HaWe]

yes, matt wrote what I actually intended to say.

[walduss]

If I were you, I would use OnFwd and/or OnRev.

yes, matt wrote what I actually intended to say.

Ok, I understand. In fact actually I am using OnFwd and OnRev instead.

Anyway, as I have comment before, after some test I have detected that issue was related to Sign fuction.

Thanks.

[HaWe]

to my observations, the sign() function always works correctly.
But not everything which normally works correctly does work also properly and predictalbly when used by the advanced motor control functions...