STM32F103ZET6 用定时器级联方式输出特定数目的PWM

STM32F103ZET6里共有8个定时器，其中高级定时器有TIM1-TIM5、TIM8，共6个。

这里需要使用定时器的级联功能，ST的RM0008 REV12的P388和P399页上有说明对于特定的定时器，怎么去选择级联功能，参见表86。

我这里输出PWM的定时器是TIM2，空闲的定时器是TIM3。以TIM2为主定时器，TIM3为从定时器对TIM2的输出脉冲数进行计数。

查表可知，TIM3为从定时器选择TIM2为触发源，需要配置TS=001，即选择ITR1。

实现通过定时器控制输出PWM个数的功能，可以有如下一种配置方式：

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;

// 时基配置：配置PWM输出定时器——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);

// 输出配置：配置PWM输出定时器——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);

// 时基配置：配置脉冲计数寄存器——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; // 这里的配置值意义不大

TIM_OC1Init(TIM3, &TIM_OCInitStructure);

// 配置TIM2为主定时器

/* Select the Master Slave Mode */

TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);

/* Master Mode selection */

TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);

// 配置TIM3为从定时器

/* 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);

}

中断服务程序如下：

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); // 清除中断标志位

TIM_Cmd(TIM2, DISABLE); // 关闭定时器

TIM_Cmd(TIM3, DISABLE); // 关闭定时器

TIM2_Pulse_TIM3_Counter_OK = 1;

}

}

应用程序为：

u16 pulsecnt = 10000;

void main(void)

{

SystemSetup(); // 初始化内核和外设

TIM2_Master__TIM3_Slave_Configuration(10000);//配置TIM2的脉冲输出为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);

}

}

这种配置方式下，使用的是TIM3的比较中断，我还没试验过其他的方式，想来应该也是可以的，比如用定时器更新中断……