Lpc2000

I'm using 3 capture channels (3 signals). I have linking each signal
to an capture pin and also linked to a generic input. The captures are
configured for rising edge and falling edge and I see which the state
in IOPIN. but i'm also with problems, read stupid values.

Someone can say that will be wrong.

Thanks
         Domingos

void captura(void){

   ISR_ENTRADA();
			
	if(T1IR & TIR_CR0I){		//interrupt in channel0 (eixo dos xx)
	   T1IR |= TIR_CR0I;
	    
	    acel_cap_eixo_x();

	}

	else if(T1IR & TIR_CR1I){		//interrupcao no canal1 (eixo dos yy)
	   T1IR |= TIR_CR1I;

	   //acel_cap_eixo_y();

	}

	else if(T1IR & TIR_CR2I){		//interrupcao no canal2 (eixo dos zz)
	   T1IR |= TIR_CR2I;			//apaga a flag de interrupcao

	  // acel_cap_eixo_z();

	}

	VICSoftIntClr = (1<<VIC_TIMER1);


	VICVectAddr = 0x00000000;             // clear this interrupt from
the VIC
	ISR_SAIDA();                           // recover registers and return
}




void acel_cap_eixo_x(void){
	u32 tpu; 
	
	if(IOPIN0 & ACEL_asc_x){		//verify if rising edge
		tpu=T1CR0;
		                                             
duty_x=(float)(ACEL_T2_x-ACEL_T1_x)/(float)(tpu-ACEL_T1_x));
		ACEL_T1_x=tpu;
		
	}else{			//falling edge
		ACEL_T2_x = T1CR0;
		 
	      	}
return;
}


..........(identical function for other axes)
























Citando onestone <onestone@...>:

> 
> Can't you just use a single timer and toggle the bits in the control 
> register that set the trigger edge? I haven't studied LPC2000 in any 
> great detail yet, but this is so basic every 4,8and 16 bitter I've 
> worked with that had a capture channel could do this. Then just check 
> the edge control bits to determine if you need a result.
> 
> Al
> 
> Bill Knight wrote:
> 
> > We am doing something similar with two capture inputs to the
> > same timer.
> > - setup 1st capture input to capture the time of the rising edge
> > - setup 2nd capture input to capture the time of the falling edge
> >    and to cause an interrupt.
> > - the interrupt routine saves the difference between the two as
> >    the pulse duration.
> > - the interrupt routine could also save the raw values for period
> >    and duty cycle calculations (we don't need that so don't do it).
> > 
> > Regards
> > -Bill Knight
> > http://www.theARMPatch.com
> > 
> > 
> > On Fri, 21 Jan 2005 23:05:45 -0000, chazeltopman wrote:
> > 
> > I'm trying to capture the width of a pulse using the capture
> > timers on the LPC2106 and getting an accurate reading every
> > time has proven difficult.  The pulses are 200 to 700
> > microseconds long.  I thought that I could capture them in
> > the following way:
> > 
> > Algorithm 1:
> >    o set up capture timer channel 0 to interrupt on each edge
> >    o on interrupt check level to see if high to indicate a
> >      rising edge
> >    o if high, remember captured time and wait for falling edge
> >    o when falling edge occurs subtract rising edge time and
> >      queue up the length of the pulse
> > 
> > I implemented this algorithm and my numbers vary quite a bit.
> > If I scope the signals, they are clean so the variance is not
> > due to noise and is due to interrupt collision or a misunderstanding
> > of the timer capture.  The above algorithm will fail if another
> > interrupt occurs preventing the captured count from being read
> > before another edge transition occurs.  This is probably what is
> > happening in my case.  So I've been thinking about how else to
> > capture the two edges without software getting in the way.  The
> > only way I can think of is to use two capture inputs and a match
> > register.
> > 
> > Algorthm 2:
> >    o the first capture input captures the time on the rising edge
> >    o the second capture input captures the time on the falling edge
> >    o the match register provides a timed interrupt in which at
> >       least two edges have been captured
> > 
> > In my case I'd set it to be a millisecond since the pulse is
> > periodic with about a millisecond period (I'm really measuring the
> > duty cycle).  Then comparing the rising and falling edge capture
> > times, I can deduce whether I've captured the low pulse (falling
> > edge before rising edge) or the high pulse (rising edge before
> > falling edge) and calculate the high pulse from the captured times.
> > Also by taking a group of measurements, I should get some of
> > the high pulse and some of the low pulse.  Using this info, I
> > should be able to deduce the period as well instead of measuring
> > that independantly.
> > 
> > While this algorithm seems like it should work, it uses two inputs
> > per pulse input.  If someone else has a better idea please toss
> > it into the arena.
> > 
> > Rob
> > 
> > 
> > 
> > 
> > 
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> >
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> > 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 

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