STM32 TIM 多通道互補PWM波形輸出配置快速入門

platform：stm32f10xxx
lib：STM32F10x_StdPeriph_Lib_V3.5.0

前言

在做三相逆變的時候，需要軟件生成SVPWM波形，具體的算法需要產生三對互補的PWM，這樣可以驅動六個開關元件，stm32f103中的TIM1高級定時器支持產生三路互補PWM波形，下面進一步學習。

PWM產生的原理

TIM1的OC模塊，可以產生PWM波形，具體步驟；

• 寄存器TIMx CNT每過一個時鍾周期就會加1；
• 然后TIMx CNT的值與TIMx CCER進行比較；
• 最終改變OC上的有效電平；
  以上只需要配置好TIM1的寄存器即可，無需再編程干預，當然可以動態修改TIMx CCER的值，從而改變占空比。可以參考下圖；
  

PWM模式

這里主要對PWM模式進行配置的時候做一下區分，存在以下兩種情況；

• TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
• TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;

那么TIM_OCMode_PWM1和TIM_OCMode_PWM2有什么區別呢？

• TIM_OCMode_PWM1 PWM模式1
  在向上計數時，一旦TIMx_CNT<TIMx_CCR1時通道1為有效電平，否則為無效電平
  在向下計數時，一旦TIMx_CNT>TIMx_CCR1時通道1為無效電平(OC1REF=0)，否則為有效 電平(OC1REF=1)。
• TIM_OCMode_PWM2 PWM模式2
  在向上計數時，一旦TIMx_CNT<TIMx_CCR1時通道1為無效電平，否則為有效電平
  在向下計數時，一旦TIMx_CNT>TIMx_CCR1時通道1為有效電平，否則為無效電平。

死區插入和剎車功能

互補PWM還支持插入死區時間，最主要的寄存器是TIMx_BDTR，在標准庫中把相關的變量封裝到TIM_BDTRInitTypeDef結構體中；具體如下；

typedef struct
{

  uint16_t TIM_OSSRState;        /*!< Specifies the Off-State selection used in Run mode. This parameter can be a value of @ref OSSR_Off_State_Selection_for_Run_mode_state */

  uint16_t TIM_OSSIState;        /*!< Specifies the Off-State used in Idle state. This parameter can be a value of @ref OSSI_Off_State_Selection_for_Idle_mode_state */

  uint16_t TIM_LOCKLevel;        /*!< Specifies the LOCK level parameters. This parameter can be a value of @ref Lock_level */ 

  uint16_t TIM_DeadTime;         /*!< Specifies the delay time between the switching-off and the switching-on of the outputs. This parameter can be a number between 0x00 and 0xFF */

  uint16_t TIM_Break;            /*!< Specifies whether the TIM Break input is enabled or not. This parameter can be a value of @ref Break_Input_enable_disable */

  uint16_t TIM_BreakPolarity;    /*!< Specifies the TIM Break Input pin polarity. This parameter can be a value of @ref Break_Polarity */

  uint16_t TIM_AutomaticOutput;  /*!< Specifies whether the TIM Automatic Output feature is enabled or not. This parameter can be a value of @ref TIM_AOE_Bit_Set_Reset */
} TIM_BDTRInitTypeDef;

相關的含義看注釋可以知道大概意思；這里整理了幾個比較重要的變量；

• 死區時間TIM_DeadTime的計算；TIMx_BDTR的低八位的配置決定了死區的時間；
  UTG[7:0]: 死區發生器設置 (Dead-time generator setup)
  這些位定義了插入互補輸出之間的死區持續時間。假設DT表示其持續時間：

DTG[7:5]=0xx => DT=DTG[7:0] × Tdtg	Tdtg = TDTS；
DTG[7:5]=10x => DT=(64+DTG[5:0]) × Tdtg	Tdtg = 2 × TDTS；
DTG[7:5]=110 => DT=(32+DTG[4:0]) × Tdtg	Tdtg = 8 × TDTS；
DTG[7:5]=111 => DT=(32+DTG[4:0])× Tdtg	Tdtg = 16 × TDTS；

例：若TDTS = 125ns(8MHZ)，可能的死區時間為：
0到15875ns，若步長時間為125ns；
16us到31750ns，若步長時間為250ns；
32us到63us，若步長時間為1us；
64us到126us，若步長時間為2us；
注：一旦LOCK級別(TIMx_BDTR寄存器中的LOCK位)設為1、 2或3，則不能修改這些位。

• TIM_Break 則表示是否決定使用剎車，如果發生錯誤，則可以通過剎車，第一時間停止PWM波形的產生，從而保證了系統的安全性；

代碼實現

#include "stm32f10x.h"
#include "svpwm_driver.h"
#include "stm32f10x_tim.h"
#include "stm32f10x_it.h"
#include <stdio.h>

#define SVPWM_USE_BDT 1
#define USE_HARD_PWM 1
/** * @brief Configures the different system clocks. * @param None * @retval None */
void pwm_rcc_init(void)
{
  /* TIM1, GPIOA, GPIOB, GPIOE and AFIO clocks enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1 | RCC_APB2Periph_GPIOA | 
                         RCC_APB2Periph_AFIO |
                         RCC_APB2Periph_GPIOB, ENABLE);
}

void pwm_cnt_irq_init(void)
{
	
}

/** * @brief Configure the TIM1 Pins. * @param None * @retval None * @note * PA8 /T1_CH1 ---> HIn3 * PA9 /T1_CH2 ---> HIn2 * PA10/T1_CH3 ---> HIn1 * Out2 ---> PA0/ADC0 * Out3 ---> PA1/ADC1 * PB15/T1_CHN3 ---> LIn1 * PB14/T1_CHN2 ---> LIn2 * PB13/T1_CHN1 ---> LIn3 */
void pwm_pin_init(void)
{
	GPIO_InitTypeDef GPIO_InitStructure;

	/* GPIOA Configuration: Channel 1, 2 and 3 as alternate function push-pull */
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 ;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOA, &GPIO_InitStructure);

	/* GPIOB Configuration: Channel 1N, 2N and 3N as alternate function push-pull */
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
	
	GPIO_Init(GPIOB, &GPIO_InitStructure);
}

void pwm_tim_init(void){

	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef  TIM_OCInitStructure;
	TIM_BDTRInitTypeDef      TIM_BDTRInitStructure;
// NVIC_InitTypeDef NVIC_InitStructure;
	uint16_t TimerPeriod = 0;
	uint16_t Channel1Pulse = 0, Channel2Pulse = 0, Channel3Pulse = 0;

	/* TIM1 Configuration --------------------------------------------------- Generate 7 PWM signals with 4 different duty cycles: TIM1CLK = SystemCoreClock, Prescaler = 0, TIM1 counter clock = SystemCoreClock SystemCoreClock is set to 72 MHz for Low-density, Medium-density, High-density and Connectivity line devices and to 24 MHz for Low-Density Value line and Medium-Density Value line devices The objective is to generate 7 PWM signal at 17.57 KHz: - TIM1_Period = (SystemCoreClock / 17570) - 1 The channel 1 and channel 1N duty cycle is set to 50% The channel 2 and channel 2N duty cycle is set to 50% The channel 3 and channel 3N duty cycle is set to 50% The Timer pulse is calculated as follows: - ChannelxPulse = DutyCycle * (TIM1_Period - 1) / 100 ----------------------------------------------------------------------- */
	TimerPeriod = (SYS_FRQ / PWM_FRQ ) - 1;
	/* Compute CCR1 value to generate a duty cycle at 50% for channel 1 and 1N */
	Channel1Pulse = (uint16_t) (((uint32_t) PWM_DUTY * (TimerPeriod - 1)) / 100);
	/* Compute CCR2 value to generate a duty cycle at 37.5% for channel 2 and 2N */
	Channel2Pulse = (uint16_t) (((uint32_t) PWM_DUTY * (TimerPeriod - 1)) / 100);
	/* Compute CCR3 value to generate a duty cycle at 25% for channel 3 and 3N */
	Channel3Pulse = (uint16_t) (((uint32_t) PWM_DUTY * (TimerPeriod - 1)) / 100);

	//TIM_DeInit(TIM1);

	/* Time Base configuration */
	TIM_TimeBaseStructure.TIM_Prescaler = TIM_PSCReloadMode_Update;
	//TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_CenterAligned2;
	TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
	TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
	TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

	TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
	/* TIM_ClearFlag(TIM1, TIM_FLAG_Update); TIM_ITConfig(TIM1,TIM_IT_Update, ENABLE); NVIC_InitStructure.NVIC_IRQChannel = TIM1_UP_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x02; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); */
	/* Channel 1, 2, 3 Configuration in PWM mode */
	#if USE_HARD_PWM

	/** TIM_OCMode_PWM1 PWM模式1 在向上計數時，一旦TIMx_CNT<TIMx_CCR1時通道1為有效電平，否則為無效電平 在向下計數時，一旦TIMx_CNT>TIMx_CCR1時通道1為無效電平(OC1REF=0)，否則為有效 電平(OC1REF=1)。 TIM_OCMode_PWM2 PWM模式2 在向上計數時，一旦TIMx_CNT<TIMx_CCR1時通道1為無效電平，否則為有效電平 在向下計數時，一旦TIMx_CNT>TIMx_CCR1時通道1為有效電平，否則為無效電平。 */	
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
	TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
	TIM_OCInitStructure.TIM_Pulse = Channel1Pulse;
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
	TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCPolarity_High;
	TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
	TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;
	
	TIM_OC1Init(TIM1, &TIM_OCInitStructure);
	
	TIM_OCInitStructure.TIM_Pulse = Channel2Pulse;
	TIM_OC2Init(TIM1, &TIM_OCInitStructure);
	
	TIM_OCInitStructure.TIM_Pulse = Channel3Pulse;
	TIM_OC3Init(TIM1, &TIM_OCInitStructure);
	
	TIM_OC1PreloadConfig(TIM1,TIM_OCPreload_Enable);
	TIM_OC2PreloadConfig(TIM1,TIM_OCPreload_Enable);
	TIM_OC3PreloadConfig(TIM1,TIM_OCPreload_Enable);
	
	#endif 

#if SVPWM_USE_BDT
	TIM_BDTRInitStructure.TIM_OSSRState = TIM_OSSRState_Enable;
	TIM_BDTRInitStructure.TIM_OSSIState = TIM_OSSIState_Enable;
	TIM_BDTRInitStructure.TIM_LOCKLevel = TIM_LOCKLevel_OFF;
	TIM_BDTRInitStructure.TIM_DeadTime = 30;
	TIM_BDTRInitStructure.TIM_Break = TIM_Break_Disable;			   
	TIM_BDTRInitStructure.TIM_BreakPolarity = TIM_BreakPolarity_Low;
	TIM_BDTRInitStructure.TIM_AutomaticOutput = TIM_AutomaticOutput_Disable;
	TIM_BDTRConfig(TIM1, &TIM_BDTRInitStructure);
#endif 
	TIM_CCPreloadControl(TIM1,ENABLE);
	/* TIM1 counter enable */	
	TIM_Cmd(TIM1, ENABLE);
	/* TIM1 Main Output Enable */
	TIM_CtrlPWMOutputs(TIM1, ENABLE);
}

void pwm_init(void){
	pwm_rcc_init();
	pwm_pin_init();
	pwm_cnt_irq_init();
	pwm_tim_init();
}

int32_t get_pwm_period(void){
	return (int32_t)((SYS_FRQ / PWM_FRQ ) - 1);
}

void pwm_reset_duty_cnt(uint8_t index, int16_t cnt){
	if(cnt <= 0){
		cnt = get_pwm_period()/2;
	}
	switch(index){
		case 1:
			TIM1->CCR1 = (uint16_t)cnt;
		break;
		case 2:
			TIM1->CCR2 = (uint16_t)cnt;
		break;
		case 3:
			TIM1->CCR3 = (uint16_t)cnt;		
		break;
	}	
}

void pwm_disable(void){
	TIM_CtrlPWMOutputs(TIM1, DISABLE);
}

void pwm_enable(void){
	TIM_CtrlPWMOutputs(TIM1, ENABLE);
}

以上代碼主要實現以下幾個功能；

• IM1定時器時鍾，使用中央對齊模式1，則會產生上溢信號；
• PWM模式設置為TIM_OCMode_PWM1；
• 加入了死區；
• 占空比 50%；
  具體如下圖所示；
  
  

參考

http://www.stmcu.org.cn/module/forum/thread-613602-1-1.html