Posted on October 25, 2013 at 12:27Hello everyone,
I am trying to interface a CCD to STM32f4 discovery kit. I need to generate a clock of 4MHz and toggle couple of pins when the clock is high to to get the output from CCD.
I referred some examples from ST peripheral library. And I configured Timer 8 to generate the update interrupt after every 125nsec so that i can toggle a pin in interrupt and generate clock of 4 MHz Also I can monitor the clock pin status and toggle some other pin as per my requirement. But the maximum freq by which i am able to toggle the pin is 875 KHz.
Below is the timer 8 config function and the ISR
void TIM8_Config(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
/* TIM1 clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8, ENABLE);
/* Enable the TIM1 gloabal Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = TIM8_UP_TIM13_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 15;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 15;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
PrescalerValue = (uint16_t) ((SystemCoreClock /2) / 8000000) - 1;
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 1;//665;
TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);
/* Prescaler configuration */
TIM_PrescalerConfig(TIM8, PrescalerValue, TIM_PSCReloadMode_Immediate);
/* TIM Interrupts enable */
TIM_ITConfig(TIM8, TIM_IT_Update, ENABLE);
/* TIM1 counter enable */
TIM_Cmd(TIM8, ENABLE);
}
//following is the interrupt routine
void TIM8_UP_TIM13_IRQHandler(void)
{
if (TIM_GetITStatus(TIM8, TIM_IT_Update) != RESET)
{
TIM_ClearITPendingBit(TIM8, TIM_IT_Update);
fnTogglePin(CCD1_MC); // using this function i am toggle the pin to generate clock
}
}
Is this possible what ever I am trying to achieve using timer 8?
please help me in using this timer to generate freq from 4 MHz to 8 Mhz
What value should i put in Prescalar and time period while config?
One more thing, i know that using PWM I can generate clock of requried freq on specific port pins. but in that case I won't come to know when my port pin has gone high. I actually want to monitor the clock output generated by microcontroller.
Please guide to achieve the requriement.
Thanks..
