main.c

/*********************************************

    標(biāo)題：操作USART的練習(xí)

    軟件平臺(tái)：MDK-ARM Standard Version4.70

    硬件平臺(tái)：stm32f4-discovery

    主頻：168M

Periph_Driver_version: V1.0.0

    描述：用一個(gè)定時(shí)器(TIM3)，實(shí)現(xiàn)四路不同頻率、占空比可調(diào)的PWM

 代碼參考自STM32F4-Discovery_FW_V1.1.0\Project\Peripheral_Examples\TIM_TimeBase

    author：大舟

    data：2013-04-13

**********************************************/

#include "stm32f4_discovery.h"

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

TIM_OCInitTypeDef  TIM_OCInitStructure;

__IO uint16_t CCR1_Val = 5000;//54618

__IO uint16_t CCR2_Val = 27309;

__IO uint16_t CCR3_Val = 13654;

__IO uint16_t CCR4_Val = 6826;

uint16_t PrescalerValue = 0;

void TIM_Config(void);

int main(void)

{

  /*!< At this stage the microcontroller clock setting is already configured, 

       this is done through SystemInit() function which is called from startup

       file (startup_stm32f4xx.s) before to branch to application main.

       To reconfigure the default setting of SystemInit() function, refer to

       system_stm32f4xx.c file

     */

  /* TIM Configuration */

  TIM_Config();

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

    TIM3 Configuration: Output Compare Timing Mode:

    In this example TIM3 input clock (TIM3CLK) is set to 2 * APB1 clock (PCLK1), 

    since APB1 prescaler is different from 1.   

      TIM3CLK = 2 * PCLK1  

      PCLK1 = HCLK / 4 

      => TIM3CLK = HCLK / 2 = SystemCoreClock /2

    To get TIM3 counter clock at 500 KHz, the prescaler is computed as follows:

       Prescaler = (TIM3CLK / TIM3 counter clock) - 1

       Prescaler = ((SystemCoreClock /2) /50 MHz) - 1

    CC1 update rate = TIM3 counter clock / CCR1_Val = 9.154 Hz @note 上面已經(jīng)將CCR1_Val改為了5000，具體頻率，見中斷的注釋

    ==> Toggling frequency = 4.57 Hz

    C2 update rate = TIM3 counter clock / CCR2_Val = 18.31 Hz

    ==> Toggling frequency = 9.15 Hz

    CC3 update rate = TIM3 counter clock / CCR3_Val = 36.62 Hz

    ==> Toggling frequency = 18.31 Hz

    CC4 update rate = TIM3 counter clock / CCR4_Val = 73.25 Hz

    ==> Toggling frequency = 36.62 Hz

    Note: 

     SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f4xx.c file.

     Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()

     function to update SystemCoreClock variable value. Otherwise, any configuration

     based on this variable will be incorrect.    

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

  /* Compute the prescaler value */

  PrescalerValue = (uint16_t) ((SystemCoreClock / 2) / 500000) - 1;//=168

  /* Time base configuration */

  TIM_TimeBaseStructure.TIM_Period = 65535;//65535

  TIM_TimeBaseStructure.TIM_Prescaler = 0;

  TIM_TimeBaseStructure.TIM_ClockDivision = 0;

  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* Prescaler configuration */

  TIM_PrescalerConfig(TIM3, PrescalerValue, TIM_PSCReloadMode_Immediate);//對(duì)84M進(jìn)行168分頻，即為500KHz

  /* Output Compare Timing Mode configuration: Channel1 */

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = CCR1_Val;

  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* Output Compare Timing Mode configuration: Channel2 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = CCR2_Val;

  TIM_OC2Init(TIM3, &TIM_OCInitStructure);

  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* Output Compare Timing Mode configuration: Channel3 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = CCR3_Val;

  TIM_OC3Init(TIM3, &TIM_OCInitStructure);

  TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* Output Compare Timing Mode configuration: Channel4 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = CCR4_Val;

  TIM_OC4Init(TIM3, &TIM_OCInitStructure);

  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* TIM Interrupts enable */  

  TIM_ITConfig(TIM3, TIM_IT_CC1 | TIM_IT_CC2 | TIM_IT_CC3 | TIM_IT_CC4, ENABLE);

  /* TIM3 enable counter */

  TIM_Cmd(TIM3, ENABLE);

  while (1);

}

/**

  * @brief  Configure the TIM IRQ Handler.

  * @param  None

  * @retval None

  */

void TIM_Config(void)

{

  NVIC_InitTypeDef NVIC_InitStructure;

  /* TIM3 clock enable */

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

  /* Enable the TIM3 gloabal Interrupt */

  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

  NVIC_Init(&NVIC_InitStructure);

  /* Initialize Leds mounted on STM32F4-Discovery board */

  STM_EVAL_LEDInit(LED4);

  STM_EVAL_LEDInit(LED3);

  STM_EVAL_LEDInit(LED5);

  STM_EVAL_LEDInit(LED6);

  /* Turn on LED4, LED3, LED5 and LED6 */

  STM_EVAL_LEDOn(LED4);

  STM_EVAL_LEDOn(LED3);

  STM_EVAL_LEDOn(LED5);

  STM_EVAL_LEDOn(LED6);

}

#ifdef  USE_FULL_ASSERT

/**

  * @brief  Reports the name of the source file and the source line number

  *         where the assert_param error has occurred.

  * @param  file: pointer to the source file name

  * @param  line: assert_param error line source number

  * @retval None

  */

void assert_failed(uint8_t* file, uint32_t line)

{

  /* User can add his own implementation to report the file name and line number,

     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  while (1)

  {}

}

#endif

/******************* (C) COPYRIGHT 2011 STMicroelectronics *****END OF FILE****/

stm32f4xx_it.c

#include "stm32f4xx_it.h"

#include "stm32f4_discovery.h"

uint16_t capture = 0;

extern __IO uint16_t CCR1_Val;

extern __IO uint16_t CCR2_Val;

extern __IO uint16_t CCR3_Val;

extern __IO uint16_t CCR4_Val;

/**

實(shí)際上當(dāng)CCR1_Val每次都變化時(shí)，就可以用來改變占空比

*/

void TIM3_IRQHandler(void)

{

/*7500為一個(gè)循環(huán)，周期為7500/500000=0.015，頻率為66.67Hz*/

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

{

TIM_ClearITPendingBit(TIM3, TIM_IT_CC1);

if(CCR1_Val==5000)

{

STM_EVAL_LEDOn(LED4); //PD12=0。ARR增加5000后，到達(dá)這條語句。

CCR1_Val=2500; //所以低電平的百分比為5000/7500=2/3。即占空比為1/3

}

else

{

STM_EVAL_LEDOff(LED4); //PD12=1

CCR1_Val=5000;

}

capture = TIM_GetCapture1(TIM3);

TIM_SetCompare1(TIM3, capture + CCR1_Val);//在原來的CCR1（即capture）基礎(chǔ)上加5000，則再過5000，又會(huì)觸發(fā)中斷

//另外，有個(gè)問題，進(jìn)入中斷時(shí)，當(dāng)ARR計(jì)數(shù)器快加到65535，而又不足5000時(shí)，不是會(huì)有數(shù)據(jù)多余，而產(chǎn)生波形的移動(dòng)嗎？

//回答：不用擔(dān)心。例如進(jìn)入中斷是，ARR=65000，65000+5000=70000>65535，那么高位會(huì)舍去，即為70000-65536=4464

//等于是來了個(gè)循環(huán)，兩次中斷間ARR的增量還是5000。所以為了波形的穩(wěn)定，初始化時(shí)，必須要有TIM_Period = 65535

}

else if (TIM_GetITStatus(TIM3, TIM_IT_CC2) != RESET)

{

TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);

/* LED3 toggling with frequency = 9.15 Hz */

STM_EVAL_LEDToggle(LED3);//PD13取反

capture = TIM_GetCapture2(TIM3);

TIM_SetCompare2(TIM3, capture + CCR2_Val);

}

else if (TIM_GetITStatus(TIM3, TIM_IT_CC3) != RESET)

{

TIM_ClearITPendingBit(TIM3, TIM_IT_CC3);

/* LED5 toggling with frequency = 18.31 Hz */

STM_EVAL_LEDToggle(LED5);//PD14取反

capture = TIM_GetCapture3(TIM3);

TIM_SetCompare3(TIM3, capture + CCR3_Val);

}

else

{

TIM_ClearITPendingBit(TIM3, TIM_IT_CC4);

/* LED6 toggling with frequency = 36.62 Hz */

STM_EVAL_LEDToggle(LED6);//PD15取反

capture = TIM_GetCapture4(TIM3);

TIM_SetCompare4(TIM3, capture + CCR4_Val);

}

}

/******************* (C) COPYRIGHT 2011 STMicroelectronics *****END OF FILE****/

ReadMe.txt

/**

  @page TIM_TimeBase TIM_TimeBase

  @verbatim

  ******************************************************************************

  * @file    TIM_TimeBase/readme.txt

  * @author  MCD Application Team

  * @version V1.0.0

  * @date    19-September-2011

  * @brief   Description of the TIM Time Base example.

  ******************************************************************************

  * THE PRESENT FIRMWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS

  * WITH CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE

  * TIME. AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY

  * DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING

  * FROM THE CONTENT OF SUCH FIRMWARE AND/OR THE USE MADE BY CUSTOMERS OF THE

  * CODING INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.

  ******************************************************************************

   @endverbatim

@par Example Description 

This example shows how to configure the TIM peripheral in Output Compare Timing 

mode with the corresponding Interrupt requests for each channel in order to generate

4 different time bases.

The TIM3CLK frequency is set to SystemCoreClock / 2 (Hz), to get TIM3 counter 

clock at 500 KHz so the Prescaler is computed as following:

   - Prescaler = (TIM3CLK / TIM3 counter clock) - 1

SystemCoreClock is set to 168 MHz for STM32F4xx Devices Revision A.

The TIM3 CC1 register value is equal to 54618, 

CC1 update rate = TIM3 counter clock / CCR1_Val = 9.154 Hz,

so the TIM3 Channel 1 generates an interrupt each 109.2ms

The TIM3 CC2 register is equal to 27309, 

CC2 update rate = TIM3 counter clock / CCR2_Val = 18.31 Hz

so the TIM3 Channel 2 generates an interrupt each 54.6ms

The TIM3 CC3 register is equal to 13654, 

CC3 update rate = TIM3 counter clock / CCR3_Val = 36.62 Hz

so the TIM3 Channel 3 generates an interrupt each 27.3ms

The TIM3 CC4 register is equal to 6826, 

CC4 update rate = TIM3 counter clock / CCR4_Val =  73.25 Hz

so the TIM3 Channel 4 generates an interrupt each 13.65ms.

When the counter value reaches the Output compare registers values, the Output 

Compare interrupts are generated and, in the handler routine, 4 pins(PD.12, PD.13,

PD.14 and PD.15) are toggled with the following frequencies: 

//引腳輸出的頻率

- PD.12:  4.57 Hz (CC1)

- PD.13:  9.15 Hz (CC2)

- PD.14: 18.31 Hz (CC3) 

- PD.15: 36.62 Hz (CC4)

@par Directory contents 

  - TIM_TimeBase/stm32f4xx_conf.h     Library Configuration file

  - TIM_TimeBase/stm32f4xx_it.c       Interrupt handlers

  - TIM_TimeBase/stm32f4xx_it.h       Interrupt handlers header file

  - TIM_TimeBase/main.c               Main program 

  - TIM_TimeBase/system_stm32f4xx.c   STM32F4xx system clock configuration file

@par Hardware and Software environment 

  - This example runs on STM32F4xx Devices Revision A.

  - This example has been tested with STM32F4-Discovery (MB997) RevA and can be

    easily tailored to any other development board.

  - STM32F4-Discovery  

    - Use LED4, LED3, LED5 and LED6 connected respectively to PD.12, PD.13,D.14 

    and PD.15 pins and connect them on an oscilloscope to show the different 

    Time Base signals.  

@par How to use it ? 

In order to make the program work, you must do the following :

 + EWARM

    - Open the TIM_TimeBase.eww workspace 

    - Rebuild all files: Project->Rebuild all

    - Load project image: Project->Debug

    - Run program: Debug->Go(F5)

 + MDK-ARM

    - Open the TIM_TimeBase.uvproj project

    - Rebuild all files: Project->Rebuild all target files

    - Load project image: Debug->Start/Stop Debug Session

    - Run program: Debug->Run (F5)    

 + TASKING

    - Open TASKING toolchain.

    - Click on File->Import, select General->'Existing Projects into Workspace' 

      and then click "Next". 

    - Browse to  TASKING workspace directory and select the project "TIM_TimeBase"   

    - Rebuild all project files: Select the project in the "Project explorer" 

      window then click on Project->build project menu.

    - Run program: Select the project in the "Project explorer" window then click 

      Run->Debug (F11)

 + TrueSTUDIO

    - Open the TrueSTUDIO toolchain.

    - Click on File->Switch Workspace->Other and browse to TrueSTUDIO workspace 

      directory.

    - Click on File->Import, select General->'Existing Projects into Workspace' 

      and then click "Next". 

    - Browse to the TrueSTUDIO workspace directory and select the project "TIM_TimeBase" 

    - Rebuild all project files: Select the project in the "Project explorer" 

      window then click on Project->build project menu.

    - Run program: Select the project in the "Project explorer" window then click 

      Run->Debug (F11)

 *

© COPYRIGHT 2011 STMicroelectronics

 */