main timer

My first timer (TIM1) is acting as the start of ADC conversion. I know I can bind some timers on the ADC events but I choose to separate that. The code snippet is:

/* Time 1 Base configuration 25µs */
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = 4;
TIM_TimeBaseStructure.TIM_Prescaler = 360;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

TIM_CKD_DIV1 is actually the main cpu clock and in my case 72MHz. The precaler is dividing that frequency to have the final period.

72MHz/360 = 200kHZ or 5µs period unit.

The minimum period you can set up is 5µs because the STM needs one complete cycle first to start counting. The TIM_Period struct member defines the final timer period you want to work with in my case:

5µs + 4 x (5µs) = 25µs or 40kHz sampling frequency.

We want our timer to just count up until it's overflowed and gives an interrupt on overflow that will be done by taking TIM_CounterMode_Up as the value for CounterMode member. To enable the interrupt on that timer following snippet is needed:

/* Enable and configure TIM1 IRQ channel */
NVIC_InitStructure.NVIC_IRQChannel = TIM1_UP_IRQChannel;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);

The only thing you need to do now is simply put some code in your int handler known as vector address. In the ride environment this is done in a separate file [target]_it.c

void TIM1_UP_IRQHandler(void)
{
TIM_ClearITPendingBit(TIM1, TIM_IT_Update );
ADC_SoftwareStartConvCmd(ADC1, ENABLE);
}

You can change the interrupt priority here but I will go into details on general interrupt handling in an other blog. Don't forget to enable the clock for the timer and the interrupt:

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1,ENABLE);

TIM_ITConfig(TIM1, TIM_IT_Update , ENABLE);

That's basically it so pretty simple and straightforward and easy to learn if you are familiar with other targets.