Posted on December 11, 2012 at 13:05Hello all experts,
I have configured the TIM2 timer of my stm32f4 discovery board. Now I want to change the prescalar value of it on the go. My code is as follows
**************************************************
void TIM2_IRQHandler(void)
{
if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
GPIO_ToggleBits(GPIOA, GPIO_Pin_5);
}
}
*************************************************
void INTTIM_Config(uint16_t numOfMilleseconds)
{
NVIC_InitTypeDef NVIC_InitStructure;
/* Enable the TIM2 gloabal Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/* TIM2 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = (500*numOfMilleseconds) - 1; // 1 MHz down to 1 KHz (1 ms)
//TIM_TimeBaseStructure.TIM_Prescaler = 84 - 1; // 24 MHz Clock down to 1 MHz (adjust per your clock)
TIM_TimeBaseStructure.TIM_Prescaler = 168-1; //168MHz Clock should be down to 1MHz
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
/* TIM IT enable */
TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
/* TIM2 enable counter */
TIM_Cmd(TIM2, ENABLE);
}
***********************************************
int main(void)
{
GPIO_config();
INTTIM_Config(50);
while (1)
{
}
}
****************************************************
Initially I configure the timer to give an interrupt in 50ms duration and it succeeds. Now I want to change the interrupt duration to 100ms when I receive my first interrupt. I tried to adding this to the irq
TIM_TimeBaseStructure.TIM_Period = (500*40) - 1; // 1 MHz down to 1 KHz (1 ms)
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
But I couldn't get the required output.
Please advice me on how to achieve this task. I know this can be done since the datasheet states the preamble can be changed on the go.
Thank you for your valuable time.
Thilina
#dividers-and-prescaler-division
