STM32F103ZET6 uses timer cascade to output a specific number of PWM

There are 8 timers in STM32F103ZET6, including 6 advanced timers including TIM1-TIM5 and TIM8.

The timer cascade function needs to be used here. Pages P388 and P399 of ST's RM0008 REV12 explain how to select the cascade function for a specific timer. See Table 86.

The timer that outputs PWM here is TIM2, and the idle timer is TIM3. TIM2 is the master timer, and TIM3 is the slave timer to count the output pulses of TIM2.

From the table, we can see that TIM3 selects TIM2 as the trigger source for the slave timer, and needs to configure TS=001, that is, select ITR1.

To achieve the function of controlling the number of PWM outputs through the timer, there can be one of the following configuration methods:

void TIM2_Master__TIM3_Slave_Configuration(u32 PulseFrequency)

{

    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

    TIM_OCInitTypeDef       TIM_OCInitStructure;

    u16 nPDTemp ;

    /* -----------------------------------------------------------------------

    TIMx Configuration: generate 4 PWM signals with 4 different duty cycles:

    TIMxCLK = 72 MHz, Prescaler = 0x0, TIMx counter clock = 72 MHz

    TIMx ARR Register = 0 => TIMx Frequency = TIMx counter clock/(ARR + 1)

    TIMx Frequency = 72MHz.

    ----------------------------------------------------------------------- */

    TIM_Cmd(TIM2, DISABLE);

    nPDTemp = 72000000UL/PulseFrequency;    

// Time base configuration: Configure PWM output timer - TIM2

    /* Time base configuration */

    TIM_TimeBaseStructure.TIM_Period          = nPDTemp-1;

    TIM_TimeBaseStructure.TIM_Prescaler       = 0;

    TIM_TimeBaseStructure.TIM_ClockDivision   = 0;

    TIM_TimeBaseStructure.TIM_CounterMode     = TIM_CounterMode_Up;

    TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

// Output configuration: Configure PWM output timer - TIM2

    /* PWM1 Mode configuration: Channel1 */

    TIM_OCInitStructure.TIM_OCMode            = TIM_OCMode_PWM1;

    TIM_OCInitStructure.TIM_OCPolarity        = TIM_OCPolarity_High;    

    TIM_OCInitStructure.TIM_OutputState       = TIM_OutputState_Enable;

    TIM_OCInitStructure.TIM_Pulse             = nPDTemp>>1;//50%

    TIM_OC1Init(TIM2, &TIM_OCInitStructure);

    TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);

// Time base configuration: Configure pulse count register - TIM3

    TIM_TimeBaseStructure.TIM_Period        = 0xFFFF;

    TIM_TimeBaseStructure.TIM_Prescaler     = 1;

    TIM_TimeBaseStructure.TIM_ClockDivision = 0;

    TIM_TimeBaseStructure.TIM_CounterMode   = TIM_CounterMode_Up;

    TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);    

    /* Output Compare Active Mode configuration: Channel1 */

    TIM_OCInitStructure.TIM_OCMode                        = TIM_OCMode_Inactive;

    TIM_OCInitStructure.TIM_OCPolarity                = TIM_OCPolarity_High;

    TIM_OCInitStructure.TIM_OutputState                = TIM_OutputState_Enable;

    TIM_OCInitStructure.TIM_Pulse = 0xFFFF; // The configuration value here is not very meaningful

    TIM_OC1Init(TIM3, &TIM_OCInitStructure);

//Configure TIM2 as the master timer

    /* Select the Master Slave Mode */

    TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);

    /* Master Mode selection */

    TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);

//Configure TIM3 as a slave timer

    /* Slave Mode selection: TIM3 */

    TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Gated);

    TIM_SelectInputTrigger(TIM3, TIM_TS_ITR1);

    TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);

    TIM_Cmd(TIM2, DISABLE);

    TIM_Cmd(TIM3, DISABLE);

}

The interrupt service routine is as follows:

u8  TIM2_Pulse_TIM3_Counter_OK = 0;

void TIM3_IRQHandler(void)

{

    if (TIM_GetITStatus(TIM3, TIM_IT_CC1) != RESET)

    {

        TIM_ClearITPendingBit(TIM3, TIM_IT_CC1); // Clear interrupt flag

        TIM_Cmd(TIM2, DISABLE); //Disable the timer

        TIM_Cmd(TIM3, DISABLE); //Disable the timer

        TIM2_Pulse_TIM3_Counter_OK = 1;

    }

}

The application is:

u16 pulsecnt = 10000;

void main(void)

{

    SystemSetup(); // Initialize the kernel and peripherals

    TIM2_Master__TIM3_Slave_Configuration(10000); //Configure TIM2 pulse output to 10k

    while(1)

    {

        TIM_ITConfig(TIM3, TIM_IT_CC1, DISABLE);        /* TIM enable counter */

        TIM_Cmd(TIM3, ENABLE);

        TIM3->CCR1  = pulsecnt;

        TIM3->CNT   = 0;

        TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);

        TIM_Cmd(TIM2, ENABLE);    /* TIM enable counter */

        while(TIM2_Pulse_TIM3_Counter_OK  == 0);

    }

}

In this configuration, the TIM3 comparison interrupt is used. I haven't tried other methods yet, but I think they should work, such as using the timer update interrupt...