STM32 MCU PWM output test

environment:

Host: XP

Development environment: MDK4.23

MCU:STM32F103CBT6

illustrate:

Use the internal 8M crystal oscillator, multiply it to 64M to supply the TIM3 timer, and generate 640K, 50% square wave on PA6 (channel 1)

source code:

Initialize the clock:

1. //Initialize RCC clock  

2. void init_rcc(void)  

3. {  

4.     //Reset the peripheral RCC register to the default value  

5.     RCC_DeInit();  

6.     //Internal crystal oscillator enabled  

7.     RCC_HSICmd(ENABLE);  

8.     //Wait for the job to stabilize  

9.     while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET);  

10.   

11.     //LSI startup, providing watchdog clock  

12.     RCC_LSICmd(ENABLE); //Enable LSI  

13.     while(RCC_GetFlagStatus(RCC_FLAG_LSIRDY)==RESET); //Wait until LSI is stable  

14.    

15.     if(1)  

16.     {  

17.         // Enable prefetch cache  

18.         FLASH_PrefetchBufferCmd( FLASH_PrefetchBuffer_Enable );  

19.         //Set the number of FLASH memory delay clock cycles. (Set to delay 2 clock cycles)  

20.         FLASH_SetLatency( FLASH_Latency_2 );  

21.         //Set the AHB clock (HCLK) (set to = system clock at this time)  

22.         RCC_HCLKConfig( RCC_SYSCLK_Div1 );  

23.         //Set the AHB clock (HCLK2) of SDIO (set to = HCLK at this time), 64M  

24.         RCC_PCLK2Config( RCC_HCLK_Div1 );  

25.         //Set APB1 peripheral clock (HCLK1) (set to = HCLK/2 at this time), 32M  

26.         RCC_PCLK1Config( RCC_HCLK_Div2 );  

27.         //ADCCLK = PCLK2/8,1M  

28.         RCC_ADCCLKConfig( RCC_PCLK2_Div8 );  

29.   

30.         //PLL clock source and frequency multiplier, here set to 64MHz  

31.         RCC_PLLConfig(RCC_PLLSource_HSI_Div2,RCC_PLLMul_16);  

32.   

33.         // Enable PLL  

34.         RCC_PLLCmd(ENABLE);  

35.         //Check if PLL is ready  

36.         while( RCC_GetFlagStatus( RCC_FLAG_PLLRDY ) == RESET ) ;  

37.         //Set PLL as system clock  

38.         RCC_SYSCLKConfig( RCC_SYSCLKSource_PLLCLK ) ;  

39.         //Check if the system clock source is PLL  

40.         while( RCC_GetSYSCLKSource() != 0x08 ) ;  

41.     }  

42. }  

Initialize IO ports and timers:

1. //Set IO port  

2. RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);  

3. GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;  

4. GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  

5. GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;     

6. GPIO_Init(GPIOA, &GPIO_InitStructure);  

7.   

8. //Set timer 3  

9. RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);  

10. //Reset the Timer to its default value  

11. TIM_DeInit(TIM3);  

12. //Use the internal clock to provide the clock source for TIM3  

13. TIM_InternalClockConfig(TIM3);  

14.   

15. timInitStruct.TIM_ClockDivision = TIM_CKD_DIV2;               

16. timInitStruct.TIM_Prescaler = 0; //Counting frequency is 64M  

17. timInitStruct.TIM_CounterMode = TIM_CounterMode_Up; //Count up  

18. timInitStruct.TIM_RepetitionCounter = 0;  

19. timInitStruct.TIM_Period = 100; //This value is actually TIMX->ARR, and can be reset when the delay starts  

20.   

21. TIM_TimeBaseInit(TIM3, &timInitStruct);  

22.   

23. //Set PWM output  

24. TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;  

25. TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  

26. TIM_OCInitStructure.TIM_Pulse = 50;  

27. TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;  

28. TIM_OC1Init(TIM3, &TIM_OCInitStructure);  

29. TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);  

30.   

31. //ARR preload buffer enable  

32. TIM_ARRPreloadConfig(TIM3, ENABLE);  

33. //Start the timer  

34. TIM_Cmd(TIM3, ENABLE);                                        

Output waveform: