counter with timer

[jorge2399]

Posted on August 22, 2006 at 14:05

counter with timer

[jorge2399]

Posted on May 17, 2011 at 09:31

hi all !

i would like to know how to implement a 16bit counter with

the st libraries. in fact, in functions, there's no timer mode as counter possible (just compare, pwm, etc, see 91x_tim.h ) ??

Have you any example ?

thx

Regards

[stefano239955_stm1_stmicro]

Posted on May 17, 2011 at 09:31

hi,

I made the timer counter in this way:

I omit the SCU init for thi peripheral...

...

TIM_StructInit(&TIM_InitStructure);

TIM_InitStructure.TIM_Mode = TIM_PWM;

TIM_InitStructure.TIM_OC1_Modes = TIM_TIMING;

TIM_InitStructure.TIM_Clock_Source = TIM_CLK_APB;

TIM_InitStructure.TIM_Prescaler = 0x00;

TIM_InitStructure.TIM_Pulse_Length_1 = 0x0030;

TIM_InitStructure.TIM_Full_Period = 0x8000;

/* Initialize the Timer 2 */

TIM_Init(TIM3, &TIM_InitStructure);

/* Enable the Timer Overflow interrupt */

TIM_ITConfig(TIM3, TIM_IT_OC2, ENABLE);

/* Enable and configure the priority of the USB_LP IRQ Channel*/

VIC_Config(TIM3_ITLine, VIC_IRQ, 0);

VIC_ITCmd(TIM3_ITLine, ENABLE);

....

// irq handler

void Timer3_irq()

{

.. your code ..

/*Clear the TIM OC1 flag */

TIM_ClearFlag(TIM3, TIM_FLAG_OC2);

}

#define TIMER_TICKS(nsec) ( ((PERIPHERAL_CLOCK / 1000000) * nsec) / 1000 )

// to set the timer period in ticks

inline void SetTimerPeriod(u32 per)

{

static unsigned int old_per=0;

if (old_per == per)

{

return;

}

old_per = per;

s_u32 *p = (s_u32*)&per;

if (p->h)

{

TIM_PrescalerConfig(TIM3, p->h & 0x00FF);

per /= p->h + 1;

}

else

{

TIM_PrescalerConfig(TIM3, p->h & 0x00FF);

}

TIM_SetPulse(TIM3, TIM_OC2_Channel, per);

}

[jorge2399]

Posted on May 17, 2011 at 09:31

that's works well !! Thanx stevejamal :D

I have a little problem :when I want to change TIM_CLK_APB in order to

increase my frequecy of timer, the timer is blocked (no interruptions) ?

(with oscillator of 25mhz). Can't go over 32khz ! !

So,What Is the a limitation in frequency for timers?

[stefano239955_stm1_stmicro]

Posted on May 17, 2011 at 09:31

I don't understand exactly what are you doing, sorry :)

For what I read in the ref. manual you can chose from an external

clock or a Peripheral clock divided by prescaler..

Check the setting of APBDIV in the SCU_CLKCTRL.

I'm working with a Peripheral clock of 96MHz...

theoretically you can work with a tick of 1usec or less.

Unfortunately the irq routine require a certain time to be served ;)