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MSP430 TimerB Capture compare problem

Started by lewis ●April 27, 2006
Hi,

I'm stuck with a problem implementing a capture compare on TIMER B. 
I have toggled a pin in the ISR and measured the waveform on the 
CRO.  The ISR triggers as expected after every 50ms , but after some 
time (quite random) the timer misfires i.e. i get a shorter duration 
pulse.
I have pasted the code below.

Thanx once again for ur help.

Regards,
Lewis
///////////////////////////////////////////////////////////////////

 #include <msp430x14x.h>
void
main(void)
{
  unsigned int i;
  P4DIR |= BIT6;
  WDTCTL = WDTPW + WDTHOLD;// Watchdog Timer Control disabled
  BCSCTL1 = 0; 
  BCSCTL2 = SELM1 + SELS;                       
  do  
  {
    IFG1 &= ~OFIFG;
    for (i=0xFFFF; i>0; i--); 
  }
  while (IFG1 & OFIFG);
  TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
  TBCCTL0 = CCIE;
  TBCCR0 = 6380;
  _EINT();
 while(1)
 {
 }
}


void Timer_B0(void) __interrupt[TIMERB0_VECTOR]
{
  TBCCR0 += 6380;
  P4OUT ^= BIT6;
}
///////////////////////////////////////////////////////////////////

Beginning Microcontrollers with the MSP430

Reply by John Heenan ●April 27, 20062006-04-27
As well as a capture interrupt you have enabled the TimerB overflow 
interrupt.

Replace
   TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
with
   TBCTL = TBSSEL0 + MC0 + TBCLR;

John Heenan


--- In msp430@msp4..., "lewis" <oldrine@...> wrote:
>
> Hi,
> 
> I'm stuck with a problem implementing a capture compare on TIMER B. 
> I have toggled a pin in the ISR and measured the waveform on the 
> CRO.  The ISR triggers as expected after every 50ms , but after 
some 
> time (quite random) the timer misfires i.e. i get
a shorter 
duration 
> pulse.
> I have pasted the code below.
> 
> Thanx once again for ur help.
> 
> Regards,
> Lewis
> ///////////////////////////////////////////////////////////////////
> 
>  #include <msp430x14x.h>
> void
> main(void)
> {
>   unsigned int i;
>   P4DIR |= BIT6;
>   WDTCTL = WDTPW + WDTHOLD;// Watchdog Timer Control disabled
>   BCSCTL1 = 0; 
>   BCSCTL2 = SELM1 + SELS;                       
>   do  
>   {
>     IFG1 &= ~OFIFG;
>     for (i=0xFFFF; i>0; i--); 
>   }
>   while (IFG1 & OFIFG);
>   TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
>   TBCCTL0 = CCIE;
>   TBCCR0 = 6380;
>   _EINT();
>  while(1)
>  {
>  }
> }
> 
> 
> void Timer_B0(void) __interrupt[TIMERB0_VECTOR]
> {
>   TBCCR0 += 6380;
>   P4OUT ^= BIT6;
> }
> ///////////////////////////////////////////////////////////////////
>
Reply by lewis ●April 27, 20062006-04-27
Hi John,
Thnx a lot !  I just tried remooving the TBIE but found that the 
timer still misfires. I am using a 8MHz crystal on XT2 and the 
regular 32K as crystal 1.The CPU is running at 8Mhz and Timer B is 
clocked at 32K from ACLK.
Regards,
Lewis


--- In msp430@msp4..., "John Heenan" <l10@...> wrote:
>
> As well as a capture interrupt you have enabled the TimerB 
overflow 
> interrupt.
> 
> Replace
>    TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
> with
>    TBCTL = TBSSEL0 + MC0 + TBCLR;
> 
> John Heenan
> 
> 
> --- In msp430@msp4..., "lewis" <oldrine@> wrote:
> >
> > Hi,
> > 
> > I'm stuck with a problem implementing a capture compare on TIMER 
B. 
> > I have toggled a pin in the ISR and measured
the waveform on the 
> > CRO.  The ISR triggers as expected after every 50ms , but after 
> some 
> > time (quite random) the timer misfires i.e. i get a shorter 
> duration 
> > pulse.
> > I have pasted the code below.
> > 
> > Thanx once again for ur help.
> > 
> > Regards,
> > Lewis
> 
> ///////////////////////////////////////////////////////////////////
> > 
> >  #include <msp430x14x.h>
> > void
> > main(void)
> > {
> >   unsigned int i;
> >   P4DIR |= BIT6;
> >   WDTCTL = WDTPW + WDTHOLD;// Watchdog Timer Control disabled
> >   BCSCTL1 = 0; 
> >   BCSCTL2 = SELM1 + SELS;                       
> >   do  
> >   {
> >     IFG1 &= ~OFIFG;
> >     for (i=0xFFFF; i>0; i--); 
> >   }
> >   while (IFG1 & OFIFG);
> >   TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
> >   TBCCTL0 = CCIE;
> >   TBCCR0 = 6380;
> >   _EINT();
> >  while(1)
> >  {
> >  }
> > }
> > 
> > 
> > void Timer_B0(void) __interrupt[TIMERB0_VECTOR]
> > {
> >   TBCCR0 += 6380;
> >   P4OUT ^= BIT6;
> > }
> 
> ///////////////////////////////////////////////////////////////////
> >
>
Reply by Michael Iverson ●April 27, 20062006-04-27
Lewis,

  You also may want to be running in continuous mode ( MC_2 ).

Cheers,

Michael

-----Original Message-----
From: msp430@msp4... [mailto:msp430@msp4...] On Behalf
Of lewis
Sent: Thursday, April 27, 2006 12:28 PM
To: msp430@msp4...
Subject: [msp430] Re: MSP430 TimerB Capture compare problem

Hi John,
Thnx a lot !  I just tried remooving the TBIE but found that the timer
still misfires. I am using a 8MHz crystal on XT2 and the regular 32K as
crystal 1.The CPU is running at 8Mhz and Timer B is clocked at 32K from
ACLK.
Regards,
Lewis


--- In msp430@msp4..., "John Heenan" <l10@...> wrote:
>
> As well as a capture interrupt you have enabled the TimerB
overflow 
> interrupt.
> 
> Replace
>    TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ; with
>    TBCTL = TBSSEL0 + MC0 + TBCLR;
> 
> John Heenan
> 
> 
> --- In msp430@msp4..., "lewis" <oldrine@> wrote:
> >
> > Hi,
> > 
> > I'm stuck with a problem implementing a capture compare on TIMER
B. 
> > I have toggled a pin in the ISR and measured
the waveform on the 
> > CRO.  The ISR triggers as expected after every 50ms , but after
> some
> > time (quite random) the timer misfires i.e. i get a shorter
> duration
> > pulse.
> > I have pasted the code below.
> > 
> > Thanx once again for ur help.
> > 
> > Regards,
> > Lewis
> 
> ///////////////////////////////////////////////////////////////////
> > 
> >  #include <msp430x14x.h>
> > void
> > main(void)
> > {
> >   unsigned int i;
> >   P4DIR |= BIT6;
> >   WDTCTL = WDTPW + WDTHOLD;// Watchdog Timer Control disabled
> >   BCSCTL1 = 0; 
> >   BCSCTL2 = SELM1 + SELS;                       
> >   do  
> >   {
> >     IFG1 &= ~OFIFG;
> >     for (i=0xFFFF; i>0; i--); 
> >   }
> >   while (IFG1 & OFIFG);
> >   TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
> >   TBCCTL0 = CCIE;
> >   TBCCR0 = 6380;
> >   _EINT();
> >  while(1)
> >  {
> >  }
> > }
> > 
> > 
> > void Timer_B0(void) __interrupt[TIMERB0_VECTOR] {
> >   TBCCR0 += 6380;
> >   P4OUT ^= BIT6;
> > }
> 
> ///////////////////////////////////////////////////////////////////
> >
>






.

 
Yahoo! Groups Links
Reply by lewis ●April 27, 20062006-04-27
Hi Michael,

I just configured the timer as suggested and it seems to be wrkin 
fine. Thanx a million.

Regards,
Lewis

--- In msp430@msp4..., "Michael Iverson" <miverson@...> 
wrote:
>
> Lewis,
> 
>   You also may want to be running in continuous mode ( MC_2 ).
> 
> Cheers,
> 
> Michael
> 
> -----Original Message-----
> From: msp430@msp4... [mailto:msp430@msp4...] On 
Behalf
> Of lewis
> Sent: Thursday, April 27, 2006 12:28 PM
> To: msp430@msp4...
> Subject: [msp430] Re: MSP430 TimerB Capture compare problem
> 
> Hi John,
> Thnx a lot !  I just tried remooving the TBIE but found that the 
timer
> still misfires. I am using a 8MHz crystal on XT2
and the regular 
32K as
> crystal 1.The CPU is running at 8Mhz and Timer B
is clocked at 32K 
from
> ACLK.
> Regards,
> Lewis
> 
> 
> --- In msp430@msp4..., "John Heenan" <l10@> wrote:
> >
> > As well as a capture interrupt you have enabled the TimerB
> overflow 
> > interrupt.
> > 
> > Replace
> >    TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ; with
> >    TBCTL = TBSSEL0 + MC0 + TBCLR;
> > 
> > John Heenan
> > 
> > 
> > --- In msp430@msp4..., "lewis" <oldrine@> wrote:
> > >
> > > Hi,
> > > 
> > > I'm stuck with a problem implementing a capture compare on 
TIMER
> B. 
> > > I have toggled a pin in the ISR and measured the waveform on 
the 
> > > CRO.  The ISR triggers as expected after
every 50ms , but after
> > some
> > > time (quite random) the timer misfires i.e. i get a shorter
> > duration
> > > pulse.
> > > I have pasted the code below.
> > > 
> > > Thanx once again for ur help.
> > > 
> > > Regards,
> > > Lewis
> > 
> 
> ///////////////////////////////////////////////////////////////////
> > > 
> > >  #include <msp430x14x.h>
> > > void
> > > main(void)
> > > {
> > >   unsigned int i;
> > >   P4DIR |= BIT6;
> > >   WDTCTL = WDTPW + WDTHOLD;// Watchdog Timer Control disabled
> > >   BCSCTL1 = 0; 
> > >   BCSCTL2 = SELM1 + SELS;                       
> > >   do  
> > >   {
> > >     IFG1 &= ~OFIFG;
> > >     for (i=0xFFFF; i>0; i--); 
> > >   }
> > >   while (IFG1 & OFIFG);
> > >   TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
> > >   TBCCTL0 = CCIE;
> > >   TBCCR0 = 6380;
> > >   _EINT();
> > >  while(1)
> > >  {
> > >  }
> > > }
> > > 
> > > 
> > > void Timer_B0(void) __interrupt[TIMERB0_VECTOR] {
> > >   TBCCR0 += 6380;
> > >   P4OUT ^= BIT6;
> > > }
> > 
> 
> ///////////////////////////////////////////////////////////////////
> > >
> >
> 
> 
> 
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
>
Reply by Adriano Caye ●May 2, 20062006-05-02
Your problem seems to be that you increment TBCCR0 in the ISR. I suggest 
you to try NOT to increment TBCCR0 inside the ISR, let it unchanged. I 
think that the shorter pulse happens when TBCCR0 overflows, because in 
this situation it would have a smaller value.

Regards,
Adriano.


lewis wrote:
> Hi John,
> Thnx a lot !  I just tried remooving the TBIE but found that the 
> timer still misfires. I am using a 8MHz crystal on XT2 and the 
> regular 32K as crystal 1.The CPU is running at 8Mhz and Timer B is 
> clocked at 32K from ACLK.
> Regards,
> Lewis
> 
> 
> --- In msp430@msp4..., "John Heenan" <l10@...> wrote:
> 
>>As well as a capture interrupt you have enabled the TimerB 
> 
> overflow 
> 
>>interrupt.
>>
>>Replace
>>   TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
>>with
>>   TBCTL = TBSSEL0 + MC0 + TBCLR;
>>
>>John Heenan
>>
>>
>>--- In msp430@msp4..., "lewis" <oldrine@> wrote:
>>
>>>Hi,
>>>
>>>I'm stuck with a problem implementing a capture compare on
TIMER 
> 
> B. 
> 
>>>I have toggled a pin in the ISR and measured the waveform on the 
>>>CRO.  The ISR triggers as expected after every 50ms , but after 
>>
>>some 
>>
>>>time (quite random) the timer misfires i.e. i get a shorter 
>>
>>duration 
>>
>>>pulse.
>>>I have pasted the code below.
>>>
>>>Thanx once again for ur help.
>>>
>>>Regards,
>>>Lewis
>>
>>///////////////////////////////////////////////////////////////////
>>
>>> #include <msp430x14x.h>
>>>void
>>>main(void)
>>>{
>>>  unsigned int i;
>>>  P4DIR |= BIT6;
>>>  WDTCTL = WDTPW + WDTHOLD;// Watchdog Timer Control disabled
>>>  BCSCTL1 = 0; 
>>>  BCSCTL2 = SELM1 + SELS;                       
>>>  do  
>>>  {
>>>    IFG1 &= ~OFIFG;
>>>    for (i=0xFFFF; i>0; i--); 
>>>  }
>>>  while (IFG1 & OFIFG);
>>>  TBCTL = TBSSEL0 + MC0 + TBCLR + TBIE ;
>>>  TBCCTL0 = CCIE;
>>>  TBCCR0 = 6380;
>>>  _EINT();
>>> while(1)
>>> {
>>> }
>>>}
>>>
>>>
>>>void Timer_B0(void) __interrupt[TIMERB0_VECTOR]
>>>{
>>>  TBCCR0 += 6380;
>>>  P4OUT ^= BIT6;
>>>}
>>
>>///////////////////////////////////////////////////////////////////
>>
> 
> 
> 
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
>
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