Posted on April 22, 2012 at 08:16I have configured my time 1 to operate in the PWM mode1 to generate a signal of fixed duty cycle. I want the generate an update INT every 4 th overflow of the TIM1 CNT . I have loaded value 4 into my repetition counter, which should decrement each time the CNT in TIM1 overflows and should generate an update INT when it reaches 0. I compute the duty cycle in the ISR and load it onto the preload registers.
The registers which i configure for the timer to operate in the above mentioned mode are given below:
TIM1 CR1
URS -> 1 // update request source
TIM1 RCR
RCR -> 4 // loads 4 into the reconfiguration register
TIM1 DIER
UIE -> 1 // update interrupt enable
A snippet of the code when in i initialize the registers is posted below:
int main(void)
{
/* TIM Configuration */
TIM_Config();
/* Compute the prescaler value */
PrescalerValue = (uint16_t) ((SystemCoreClock /2) / 28000000) - 1;
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 665;
TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_RepetitionCounter=4;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
/* Configures the TIMx Prescaler. */
TIM_PrescalerConfig(TIM1,PrescalerValue,TIM_PSCReloadMode_Update);
/* PWM1 Mode configuration: Channel3 */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = CCR1_Val;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);
/* Configures the TIM1 Update Request Interrupt source (SETS the CR1->URS bit)*/
TIM_UpdateRequestConfig(TIM1,TIM_UpdateSource_Regular);
/*Enables or disables TIM1 peripheral Preload register on ARR */
TIM_ARRPreloadConfig(TIM1, ENABLE);
/* TIM1 enable counter */
TIM_Cmd(TIM1, ENABLE);
/*Enables or disables the TIM peripheral Main Outputs*/
TIM_CtrlPWMOutputs(TIM1, ENABLE);
/* Enables or disables the specified TIM interrupts */
TIM_ITConfig(TIM1,TIM_IT_Update, ENABLE);
while (1)
{}
}
If correct me if i have missed any steps in configuring TIM1 to generate an update interrupt every 4th overflow of the CNT ( which is achieved using the Repetition counter).
-Regards
-Gandalf
