RCC初始化学习

一、设置RCC时钟

1. //#define SYSCLK_HSE
   
2. #define SYSCLK_FREQ_20MHz
   
3. //#define SYSCLK_FREQ_36MHz
   
4. //#define SYSCLK_FREQ_48MHz
   
5. //#define SYSCLK_FREQ_72MHz
   
6. 
   
7. /*******************************************************************************
   
8. * Function Name : SetSysClock
   
9. * Description : Configures the System clock frequency, HCLK, PCLK2 and PCLK1 prescalers.
   
10. * Input : None
    
11. * Output : None
    
12. * Return : None
    
13. *******************************************************************************/
    
14. void SetSysClock(void)
    
15. {
    
16. #if defined SYSCLK_HSE
    
17.         SetSysClockToHSE();
    
18. #elif defined SYSCLK_FREQ_20MHz
    
19.         SetSysClockTo20();
    
20. #elif defined SYSCLK_FREQ_36MHz
    
21.         SetSysClockTo36();
    
22. #elif defined SYSCLK_FREQ_48MHz
    
23.         SetSysClockTo48();
    
24. #elif defined SYSCLK_FREQ_72MHz
    
25.         SetSysClockTo72();
    
26. #endif
    
27. }

SetSysClockToHSE：

1. ErrorStatus HSEStartUpStatus;
2. /*******************************************************************************
   
3. * Function Name : SetSysClockToHSE
   
4. * Description : Selects HSE as System clock source and configure HCLK,PCLK2 and PCLK1 prescalers.
   
5. * Input : None
   
6. * Output : None
   
7. * Return : None
   
8. *******************************************************************************/
   
9. void SetSysClockToHSE(void)
   
10. {
    
11.     /* Deinitialize the RCC registers */
    
12.     RCC_DeInit();
    
13.     /* Enable the HSE */
    
14.     RCC_HSEConfig(RCC_HSE_ON);
    
15.     /* Wait till HSE is ready and if Time out is reached exit */
    
16.     HSEStartUpStatus = RCC_WaitForHSEStartUp();
    
17.     if(HSEStartUpStatus == SUCCESS)
    
18.     {
    
19.         /* Add here PLL ans system clock config */
    
20.         
    
21.         /* Enable The Prefetch Buffer */
    
22.         FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    
23.         
    
24.         /* Configure Tthe Latency cycle: Set 0 Latency cycles */
    
25.         FLASH_SetLatency(FLASH_Latency_0);
    
26.         
    
27.         /* Configure HCLK such as HCLK = SYSCLK */
    
28.         RCC_HCLKConfig(RCC_SYSCLK_Div1);
    
29.         
    
30.         /* PCLK2 = HCLK*/
    
31.         RCC_PCLK2Config(RCC_HCLK_Div1);
    
32.         
    
33.         /* PCLK1 = HCLK*/
    
34.         RCC_PCLK1Config(RCC_HCLK_Div1);
    
35.         
    
36.         /* Select HSE as system clock source*/
    
37.         RCC_SYSCLKConfig(RCC_SYSCLKSource_HSE);
    
38.         
    
39.         /* Wait till HSE is used as system clock source */
    
40.         if(RCC_GetSYSCLKSource() != 0x04)
    
41.         {
    
42.             
    
43.         }
    
44.         else
    
45.         {
    
46.             
    
47.         }
    
48.     }
    
49.     else
    
50.     {
    
51.         /* If HSE fails to start-up. */
    
52.         while(1)
    
53.         {
    
54.         }
    
55.     }
    
56. }

SetSysClockTo20：

1. /*******************************************************************************
   
2. * Function Name : SetSysClockTo20
   
3. * Description : Sets System clock frequency to 20MHz and configure HCLK, PCLK2 and PCLK1 prescalers.
   
4. * Input : None
   
5. * Output : None
   
6. * Return : None
   
7. *******************************************************************************/
   
8. void SetSysClockTo20(void)
   
9. {
   
10.     /* SYSCLK, HCLK, PCLK2 and PCLK1 configuration -----------------------------*/
    
11.     /* RCC system reset(for debug purpose) */
    
12.     RCC_DeInit();    
    
13.     
    
14.     /* Enable HSE */
    
15.     RCC_HSEConfig(RCC_HSE_ON);
    
16.     
    
17.     /* Wait till HSE is ready */
    
18.     HSEStartUpStatus = RCC_WaitForHSEStartUp();
    
19.     if(HSEStartUpStatus == SUCCESS)
    
20.     {
    
21.      /* Enable Prefetch Buffer */
    
22.         FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    
23.         
    
24.         /* Flash 0 wait state */
    
25.         FLASH_SetLatency(FLASH_Latency_0);
    
26.         
    
27.      /* HCLK = SYSCLK */
    
28.         RCC_HCLKConfig(RCC_SYSCLK_Div1);
    
29.         
    
30.      /* PCLK2 = HCLK */
    
31.         RCC_PCLK2Config(RCC_HCLK_Div1);
    
32.         
    
33.      /* PCLK1 = HCLK */
    
34.         RCC_PCLK1Config(RCC_HCLK_Div1);
    
35.         
    
36.      /* PLLCLK = (8MHz / 2) * 5 = 20 MHz */
    
37.         RCC_PLLConfig(RCC_PLLSource_HSE_Div2, RCC_PLLMul_5);
    
38.         
    
39.         /* Enable PLL */
    
40.         RCC_PLLCmd(ENABLE);
    
41.         
    
42.      /* Wait till PLL is ready */
    
43.         while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
    
44.         {
    
45.             
    
46.         }
    
47.         
    
48.      /* Select PLL as system clock source */
    
49.         RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
    
50.         
    
51.      /* Wait till PLL is used as system clock source */
    
52.         if(RCC_GetSYSCLKSource() != 0x80)
    
53.         {
    
54.         }
    
55.         else
    
56.         {
    
57.         }
    
58.     }
    
59.     else
    
60.     {
    
61.         /* If HSE fails to start-up. */
    
62.         while(1)
    
63.         {
    
64.         }
    
65.     }

SetSysClockTo36：

1. /*******************************************************************************
   
2. * Function Name : SetSysClockTo36
   
3. * Description : Sets System clock frequency to 36MHz and configure HCLK, PCLK2 and PCLK1 prescalers.
   
4. * Input : None
   
5. * Output : None
   
6. * Return : None
   
7. *******************************************************************************/
   
8. void SetSysClockTo36(void)
   
9. {
   
10.     /* RCC system reset */
    
11.     RCC_DeInit();
    
12.     /* Enable HSE */
    
13.     RCC_HSEConfig(RCC_HSE_ON);
    
14.     
    
15.     /* Wait till HSE is ready */
    
16.     HSEStartUpStatus = RCC_WaitForHSEStartUp();
    
17.     if(HSEStartUpStatus == SUCCESS)
    
18.     {
    
19.         /* Enable Prefetch Buffer*/
    
20.         FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    
21.         
    
22.         /* Flash 1 wait state */
    
23.         FLASH_SetLatency(FLASH_Latency_1);
    
24.         
    
25.         /* HCLK = SYSCLK */
    
26.         RCC_HCLKConfig(RCC_SYSCLK_Div1);
    
27.         
    
28.         /* PCLK2 = HCLK */
    
29.         RCC_PCLK2Config(RCC_HCLK_Div1);
    
30.         
    
31.         /* PCLK1 = HCLK */
    
32.         RCC_PCLK1Config(RCC_HCLK_Div1);
    
33.         
    
34.         /* PLLCLK = (8MHz / 2) * 9 = 36MHz */
    
35.         RCC_PLLConfig(RCC_PLLSource_HSE_Div2, RCC_PLLMul_9);
    
36.         
    
37.         /* Enable PLL */
    
38.         RCC_PLLCmd(ENABLE);
    
39.         
    
40.         /* Wait till PLL is ready */
    
41.         while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);
    
42.         
    
43.         /* Select PLL as system clock source */
    
44.         RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
    
45.         
    
46.         /* Wait till PLL is used as system clock source */
    
47.         if(RCC_GetSYSCLKSource() == 0x08)
    
48.         {
    
49.             
    
50.         }
    
51.         else
    
52.         {
    
53.             
    
54.         }
    
55.     }
    
56.     else
    
57.     {
    
58.         /* If HSE fails to start-up. */
    
59.         while(1)
    
60.         {
    
61.         }
    
62.     }
    
63. }

SetSysClockTo48：

1. /*******************************************************************************
   
2. * Function Name : SetSysClockTo48
   
3. * Description : Sets System clock frequency to 48MHz and configure HCLK, PCLK2 and PCLK1 prescalers.
   
4. * Input : None
   
5. * Output : None
   
6. * Return : None
   
7. *******************************************************************************/
   
8. void SetSysClockTo48(void)
   
9. {
   
10.     /* RCC system reset */
    
11.     RCC_DeInit();
    
12.     /* Enable HSE */
    
13.     RCC_HSEConfig(RCC_HSE_ON);
    
14.     
    
15.     /* Wait till HSE is ready */
    
16.     HSEStartUpStatus = RCC_WaitForHSEStartUp();
    
17.     if(HSEStartUpStatus == SUCCESS)
    
18.     {
    
19.         /* Enable Prefetch Buffer*/
    
20.         FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    
21.         
    
22.         /* Flash 1 wait state */
    
23.         FLASH_SetLatency(FLASH_Latency_1);
    
24.         
    
25.         /* HCLK = SYSCLK */
    
26.         RCC_HCLKConfig(RCC_SYSCLK_Div1);
    
27.         
    
28.         /* PCLK2 = HCLK */
    
29.         RCC_PCLK2Config(RCC_HCLK_Div1);
    
30.         
    
31.         /* PCLK1 = HCLK/2 */
    
32.         RCC_PCLK1Config(RCC_HCLK_Div2);
    
33.         
    
34.         /* PLLCLK = 8MHz * 6 = 48MHz */
    
35.         RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_6);
    
36.         
    
37.         /* Enable PLL */
    
38.         RCC_PLLCmd(ENABLE);
    
39.         
    
40.         /* Wait till PLL is ready */
    
41.         while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);
    
42.         
    
43.         /* Select PLL as system clock source */
    
44.         RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
    
45.         
    
46.         /* Wait till PLL is used as system clock source */
    
47.         if(RCC_GetSYSCLKSource() == 0x08)
    
48.         {
    
49.             
    
50.         }
    
51.         else
    
52.         {
    
53.             
    
54.         }
    
55.     }
    
56.     else
    
57.     {
    
58.         /* If HSE fails to start-up. */
    
59.         while(1)
    
60.         {
    
61.         }
    
62.     }    
    
63. }

SetSysClockTo72：

1. /*******************************************************************************
   
2. * Function Name : SetSysClockTo72
   
3. * Description : Sets System clock frequency to 72MHz and configure HCLK, PCLK2
   
4. * and PCLK1 prescalers.
   
5. * Input : None
   
6. * Output : None
   
7. * Return : None
   
8. *******************************************************************************/
   
9. void SetSysClockTo72(void)
   
10. {
    
11.     /* RCC system reset */
    
12.     RCC_DeInit();
    
13.     /* Enable HSE */
    
14.     RCC_HSEConfig(RCC_HSE_ON);
    
15.     
    
16.     /* Wait till HSE is ready */
    
17.     HSEStartUpStatus = RCC_WaitForHSEStartUp();
    
18.     if(HSEStartUpStatus == SUCCESS)
    
19.     {
    
20.         /* Enable Prefetch Buffer*/
    
21.         FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    
22.         
    
23.         /* Flash 1 wait state */
    
24.         FLASH_SetLatency(FLASH_Latency_2);
    
25.         
    
26.         /* HCLK = SYSCLK */
    
27.         RCC_HCLKConfig(RCC_SYSCLK_Div1);
    
28.         
    
29.         /* PCLK2 = HCLK */
    
30.         RCC_PCLK2Config(RCC_HCLK_Div1);
    
31.         
    
32.         /* PCLK1 = HCLK/2 */
    
33.         RCC_PCLK1Config(RCC_HCLK_Div2);
    
34.         
    
35.         /* PLLCLK = 8MHz * 6 = 48MHz */
    
36.         RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);
    
37.         
    
38.         /* Enable PLL */
    
39.         RCC_PLLCmd(ENABLE);
    
40.         
    
41.         /* Wait till PLL is ready */
    
42.         while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);
    
43.         
    
44.         /* Select PLL as system clock source */
    
45.         RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
    
46.         
    
47.         /* Wait till PLL is used as system clock source */
    
48.         if(RCC_GetSYSCLKSource() == 0x08)
    
49.         {
    
50.             
    
51.         }
    
52.         else
    
53.         {
    
54.             
    
55.         }
    
56.     }
    
57.     else
    
58.     {
    
59.         /* If HSE fails to start-up. */
    
60.         while(1)
    
61.         {
    
62.         }
    
63.     }    
    
64. }

二、中断初始化

1. /****************************************************************************
   
2. * Function Name : NVIC_Configuration
   
3. * Description : Configures Vector Table base location.
   
4. * Input : None
   
5. * Output : None
   
6. * Return : None
   
7. ****************************************************************************/
   
8. void NVIC_Configuration(void)
   
9. {
   
10.     NVIC_InitTypeDef NVIC_InitStructure;
    
11. 
    
12. #ifdef VET_TAB_RAM
    
13.     /* Set the Vector Table base location at 0x2000 0000 */
    
14.     NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);
    
15. #else
    
16.     /* Set the Vector Table base location at 0x8000 0000 */
    
17.     NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
    
18. #endif
    
19.     
    
20.     /* Enable and configure RCC global IRQ channel */
    
21.     NVIC_InitStructure.NVIC_IRQChannel = RCC_IRQn;
    
22.     NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    
23.     NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    
24.     NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    
25.     NVIC_Init(&NVIC_InitStructure);
    
26. }

三、GPIO口初始化

1. /****************************************************************************
   
2. * Function Name : LED_Init
   
3. * Description : Configures GPIOB
   
4. * Input : None
   
5. * Output : None
   
6. * Return : None
   
7. ****************************************************************************/
   
8. void LED_Init()
   
9. {
   
10.     /* Configure all the GPIOB in Output Push-Pull */
    
11.     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15 | GPIO_Pin_14;
    
12.     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    
13.     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    
14.     
    
15.     /* Enable GPIOB clock */
    
16.     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
    
17.     
    
18.     /* Initialize GPIOB*/
    
19.     GPIO_Init(GPIOB, &GPIO_InitStructure);
    
20. }

四、main函数

1. /****************************************************************************
   
2. * Function Name : main
   
3. * Description : Main program.
   
4. * Input : None
   
5. * Output : None
   
6. * Return : None
   
7. ****************************************************************************/
   
8. 
   
9. int main(void)
   
10. {
    
11.     /* Set system clock HCLK PCLK2 PCLK1 and PLLCLK */
    
12.     SetSysClock();
    
13.     
    
14.     /* Get current frequency and fill in RCC_ClockFreq */
    
15.     RCC_GetClocksFreq(&RCC_ClockFreq);
    
16.     
    
17.     /* Enable Clock Security System(CSS), this will generate an NMI exception (Non-Maskable Interrupt)
    
18.      when HSE clock fails*/
    
19.     RCC_ClockSecuritySystemCmd(ENABLE);
    
20.     
    
21.     /* NVIC configuration */
    
22.     NVIC_Configuration();
    
23.     
    
24.     /* LED configuration */
    
25.     LED_Init();
    
26.     
    
27.     /* Set the GPIOB prot pin 15 and pin 14*/
    
28.     GPIO_SetBits(GPIOB, GPIO_Pin_15 | GPIO_Pin_14);
    
29.     
    
30.     /* Output HSE clock on MCO pin */
    
31.     RCC_MCOConfig(RCC_MCO_HSE);
    
32.             
    
33.     while(1)
    
34.     {
    
35.         GPIO_Write(GPIOB, (u16)~GPIO_ReadOutputData(GPIOB));
    
36. 
    
37.         Delay(DELAY_COUNT);        
    
38.     }
    
39. }