Toggle a pin with 3.57MHz frequency

[dimasusl]

Posted on February 24, 2009 at 04:15

Toggle a pin with 3.57MHz frequency

[dimasusl]

Posted on May 17, 2011 at 13:04

I tried to make this using TIM2, but the max freq was 666.7 KHz only.

Notes:

TIM2CLK is 36 MHz.

TIM2 counter clock = TIM2CLK / (Prescaler +1)

Period = TIM2 counter clock/MyFreq

MyFreq = 3.57 MHz

Prescaler = 9

TIM2 counter clock = 3.6 MHz

Period = 1

Where are i am wrong?

Code with TIM2 init:

/* Time base configuration */

TIM_TimeBaseStructure.TIM_Period = 1;

TIM_TimeBaseStructure.TIM_Prescaler = 0;

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit( TIM2, &TIM_TimeBaseStructure );

TIM_ITConfig( TIM2, TIM_IT_Update, ENABLE );

TIM_Cmd( TIM2, ENABLE );

Interrupt handler:

void TIM2_IRQHandler(void)

{

TIM_ClearITPendingBit(TIM2, TIM_IT_Update);

GPIOB->ODR ^= (1 << 12); //PB.12

GPIOA->ODR ^= (1 << 8); //PA.8

}

[ This message was edited by: dimasusl on 23-02-2009 18:44 ]

[dimasusl]

Posted on May 17, 2011 at 13:04

So, it's work, but...

I setup TIM2 with CC2 in toggle mode (it's using pin PA.1)

/* Time base configuration */

TIM_TimeBaseStructure.TIM_Period = 1; //tick with 7.2MHz

TIM_TimeBaseStructure.TIM_Prescaler = 4;

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit( TIM2, &TIM_TimeBaseStructure );

/* Output Compare Toggle Mode configuration: Channel2 */

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse = CCR2_Val; // CCR2_Val = 0

TIM_OC2Init(TIM2, &TIM_OCInitStructure);

TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Disable);

/* TIM IT enable */

TIM_ITConfig( TIM2, TIM_IT_CC2, ENABLE );

/* TIM2 enable counter */

TIM_Cmd( TIM2, ENABLE );

GPIO setup:

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; <-- !

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

And, interrupt handler:

void TIM2_IRQHandler(void)

{

/* TIM2_CH2 toggling with frequency = 3.6 MHz */

if (TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET)

{

TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);

capture = TIM_GetCapture2(TIM2);

TIM_SetCompare2(TIM2, capture + CCR2_Val);

}

}

[ This message was edited by: dimasusl on 23-02-2009 21:42 ]

[johnspeth9]

Posted on May 17, 2011 at 13:04

It appears you're trying to fire an interrupt at your target output clock rate (3.57 MHz). I'm sorry to say that I don't think the STM32 can handle interrupts that fast. In fact, I think you maxed out your ISR rate at 666 KHz.

[johnspeth9]

Posted on May 17, 2011 at 13:04

It's a programmer exercise. Take a look at any PWM example on a timer output pin. You'll never achive the rate you're looking for with an interrupt handler. You'll need the help of the timer peripheral. The PWM example will hsow you how. You'll need to experiment. You might not be able to achieve the exact frequency you want because the clock divisors will be small.

[dimasusl]

Posted on May 17, 2011 at 13:04

Quote:

On 23-02-2009 at 20:34, Anonymous wrote:

It appears you're trying to fire an interrupt at your target output clock rate (3.57 MHz). I'm sorry to say that I don't think the STM32 can handle interrupts that fast. In fact, I think you maxed out your ISR rate at 666 KHz.

Maybe you are right, but how can i generate CLK = 3.57(3.6)MHz for my SAM module, in another way?

P.S. My oscilloscope shows that this is possible

:)

[ This message was edited by: dimasusl on 23-02-2009 21:52 ]

[dimasusl]

Posted on May 17, 2011 at 13:04

Quote:

On 24-02-2009 at 00:58, Anonymous wrote:

It's a programmer exercise. Take a look at any PWM example on a timer output pin. You'll never achive the rate you're looking for with an interrupt handler. You'll need the help of the timer peripheral. The PWM example will hsow you how. You'll need to experiment. You might not be able to achieve the exact frequency you want because the clock divisors will be small.

Thank you very much. Indeed, using the example of PWM, I have achieved the desired result without interruption. This is very good, since it works the rest of the hardware (eg, USB).

P.S. But now I am well-mastered timers:)