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在微控制器領(lǐng)域，初始化參數(shù)配置階段至關(guān)重要。此時(shí)，雖無電源驅(qū)動(dòng)，但微控制器在使能信號(hào)到來前，借初始化參數(shù)配置這一精細(xì)步驟，開啟關(guān)鍵準(zhǔn)備進(jìn)程。初始化參數(shù)配置如同物理坐標(biāo)錨定、邏輯指令部署、內(nèi)在秩序預(yù)設(shè)，各參數(shù)像深埋沃土的種子，坐標(biāo)、朝向、深度經(jīng)精密計(jì)算，為未來指令運(yùn)行奠定基礎(chǔ)。

下面以國科安芯的MCU芯片AS32A601為例，詳細(xì)展示下MCU這一嚴(yán)格的設(shè)計(jì)特性：

外設(shè)檢測階段：MCU會(huì)嘗試檢測外設(shè)可用性，然后才開始執(zhí)行用戶代碼。
時(shí)鐘樹配置：系統(tǒng)時(shí)鐘(CK_SYS)、AHB、APB等總線時(shí)鐘必須在其他外設(shè)初始化前完成配置。

為什么參數(shù)要在使能前配置？

避免電平跳變：

① GPIO復(fù)用模式下，若先使能外設(shè)再配置復(fù)用選擇器，會(huì)導(dǎo)致短暫電平變化。

② 普通輸出IO默認(rèn)輸出低電平，若先使能再設(shè)置高電平，會(huì)出現(xiàn)短暫低脈沖。

防止硬件沖突：

① 時(shí)鐘使能必須在外設(shè)初始化之前，否則會(huì)導(dǎo)致外設(shè)無法正常工作。

② 寄存器默認(rèn)值可能不符合應(yīng)用需求，直接使能可能導(dǎo)致意外行為。

確保穩(wěn)定狀態(tài)：

① 外設(shè)使能前需要建立正確的時(shí)鐘源、中斷優(yōu)先級(jí)等基礎(chǔ)環(huán)境。

② 參數(shù)配置需要一定時(shí)間生效，立即使能可能導(dǎo)致功能異常。

時(shí)鐘配置

i. 通過閱讀芯片手冊，確認(rèn)好項(xiàng)目所需外設(shè)所在時(shí)鐘

ii. 確保時(shí)鐘最先配置，再去配置外設(shè)

**void** Systemclock_Init()

{

    //注意：此處需要開啟系統(tǒng)總線級(jí)的時(shí)鐘配置，具體外設(shè)時(shí)鐘配置可在各模塊初始化函數(shù)中具體開啟,具體請參考時(shí)鐘樹或者下圖注釋

    //      1. 使用串口時(shí)，由于串口掛在APB0總線下，需要在此處開啟AXIBUS3時(shí)鐘、AXI4TOAPB0時(shí)鐘以及APBBUS0時(shí)鐘。

    //      2. 使用延時(shí)函數(shù)時(shí)，需要開啟CLINT時(shí)鐘

    //      3. 使用eflash、qspi時(shí)，需要開啟AXIBUS3時(shí)鐘、AXILITEBUS2時(shí)鐘

     

    /* AXIBus3 clock operation Guide*/

    AXIBUS3_CLK_ENABLE();

    AXI4TOAPB0_CLK_ENABLE();

    APBBUS0_CLK_ENABLE();

    AXI4TOAPB1_CLK_ENABLE();

    APBBUS1_CLK_ENABLE();

    AXILITEBUS1_CLK_ENABLE();

    AXILITEBUS2_CLK_ENABLE();

    EFLASH_CLK_ENABLE();   

    PLIC_CLK_ENABLE();

    CLINT_CLK_ENABLE();

     

    SMU_PLLInitTypeDef SMU_PLLInitStruct;

    SMU_ClockInitTypeDef SMU_ClockInitStruct;

   

    /* Set PLL parameters values */

    SMU_PLLInitStruct.OscillatorType = SMU_OSCILLATORTYPE_OSC;

    SMU_PLLInitStruct.FIRCOscState = DISABLE;

    SMU_PLLInitStruct.FIRCCalibrationValue = 0x00;

    SMU_PLLInitStruct.PLLConfig.PLLState = ENABLE;

    SMU_PLLInitStruct.PLLConfig.PLLSource = SMU_PLLCLK_OSC;

    SMU_PLLInitStruct.PLLConfig.PLLDivR = 0x01;

    SMU_PLLInitStruct.PLLConfig.PLLDivQ = 0x01;

    SMU_PLLInitStruct.PLLConfig.PLLDivN = 0x14;

    SMU_PLLInitStruct.PLLConfig.PLLDivF = 0xA0;

    SMU_PLLInit(&SMU_PLLInitStruct); 

     

    /* Ensure that the EFLASH is consistent with the system clock */

    FLASH_UnlockCtrl();

    FLASH_SetCLKFreq(0xA0);

     

    /* Set System Clock parameters values */

    SMU_ClockInitStruct.SYSCLKSelect = SMU_SYSCLK_PLL;

    SMU_ClockInitStruct.AXI4Bus3CLKDiv = AXI4Bus3CLKDiv1;

    SMU_ClockInitStruct.APBBus0CLKDiv = APBBus0CLKDiv1;

    SMU_ClockInitStruct.APBBus1CLKDiv = APBBus1CLKDiv8;

    SMU_ClockInitStruct.CANX2CLKDiv = CANX2CLKDiv1;

   

    SMU_ClockInit(&SMU_ClockInitStruct);

     

    EFLASH_CLK_UPDATE_ENABLE();

    EFLASH_CLK_UPDATE_DISABLE();

 

    FLASH_LockCtrl();

     

    /* Get System Clock values */

    SMU_GetClocksFreq(&SMU_ClocksStruct);

}

GPIO初始化

i. 開始GPIO對應(yīng)時(shí)鐘

ii. 如果是復(fù)用IO，首先要配置復(fù)用

**void** GPIO_Init( **void** )

{

   GPIO_InitTypeDef  GPIO_InitStructure; 

   /*開啟GPIO所在時(shí)鐘*/

   GPIOD_CLK_ENABLE();

   GPIOG_CLK_ENABLE();

   GPIOF_CLK_ENABLE();

   /* Set GPIO multiplex mapping */

   GPIO_PinAFConfig(GPIOD, GPIO_PinSource13, GPIO_AF_CAN1);//先開啟復(fù)用模式

   GPIO_PinAFConfig(GPIOD, GPIO_PinSource14, GPIO_AF_CAN1);

  

   /* GPIO Configure */

   GPIO_StructInit(&GPIO_InitStructure);

   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;

   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

   GPIO_InitStructure.GPIO_OType = GPIO_Out_PP;

   GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_9mA;

   

   GPIO_Init(GPIOD, &GPIO_InitStructure);

   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_14;

   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;

   GPIO_InitStructure.GPIO_IType = GPIO_IPU;

   GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_9mA;

   GPIO_Init(GPIOD, &GPIO_InitStructure);

    

    /* GPIOB Configure */

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_14 | GPIO_Pin_15; 

    GPIO_InitStructure.GPIO_Mode      = GPIO_Mode_OUT;

    GPIO_InitStructure.GPIO_OType     = GPIO_Out_PP;

    GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_9mA;

     

    GPIO_Init(GPIOG, &GPIO_InitStructure); 

   

    /* GPIOB Configure */

    GPIO_InitStructure.GPIO_Pin       = GPIO_Pin_1; 

    GPIO_InitStructure.GPIO_Mode      = GPIO_Mode_IN;

    GPIO_InitStructure.GPIO_IType     = GPIO_IPU;

    GPIO_InitStructure.GPIO_OType     = GPIO_Out_PP;

    GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_9mA;

     

    GPIO_Init(GPIOF, &GPIO_InitStructure);  

}

部分外設(shè)參數(shù)配置

a) Usart

i. 開啟GPIO和外設(shè)時(shí)鐘

ii. 配置GPIO先配置復(fù)用

iii. 配置外設(shè)參數(shù)

iv. 最后使能外設(shè)

**void** User_Print_Init(uint32_t BaudRate)

{

    USART_InitTypeDef USART_InitStructure;

    GPIO_InitTypeDef  GPIO_InitStructure;

    PLIC_InitTypeDef PLIC_InitStructure;

    /*GOPI/外設(shè)時(shí)鐘使能*/

    GPIOD_CLK_ENABLE();

    USART0_CLK_ENABLE();

    /* Set GPIO multiplex mapping */

    GPIO_PinAFConfig(GPIOD, GPIO_PinSource8, GPIO_AF_USART0);       /* USART0_TX */ 開啟復(fù)用模式

    GPIO_PinAFConfig(GPIOD, GPIO_PinSource9, GPIO_AF_USART0);       /* USART0_RX */

    /* GPIO Configure */

    GPIO_InitStructure.GPIO_Pin       = GPIO_Pin_8;             

    GPIO_InitStructure.GPIO_Mode      = GPIO_Mode_OUT;

    GPIO_InitStructure.GPIO_OType     = GPIO_Out_PP;

    GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_4_5mA;

    GPIO_Init(GPIOD, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin       = GPIO_Pin_9;             

    GPIO_InitStructure.GPIO_Mode      = GPIO_Mode_IN;

    GPIO_InitStructure.GPIO_IType     = GPIO_IN_FLOATING;

    GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_4_5mA;

    GPIO_Init(GPIOD, &GPIO_InitStructure);

    /*防止配置沖突*/

    USART_DeInit(USART0);

    USART_StructInit(&USART_InitStructure);

 

    /* Initializes the USART0 */

    USART_InitStructure.USART_BaudRate     = BaudRate;

    USART_InitStructure.USART_WordLength   = USART_WordLength_8b;

    USART_InitStructure.USART_StopBits     = USART_StopBits_1;

    USART_InitStructure.USART_Parity       = USART_Parity_No;

    USART_InitStructure.USART_Mode         = USART_Mode_Rx | USART_Mode_Tx;

    USART_InitStructure.USART_OverSampling = USART_OverSampling_16;

USART_Init(USART0, &USART_InitStructure);

/*配置好相關(guān)參數(shù)后，使能USART*/

    USART_Cmd(USART0, ENABLE);

    USART_ITConfig(USART0, USART_IT_RXNE, ENABLE);

     

     /* Configer the USART0 interrupt */

    PLIC_InitStructure.PLIC_IRQChannel = USART0_IRQn;

    PLIC_InitStructure.PLIC_IRQPriority = 1;

    PLIC_InitStructure.PLIC_IRQChannelCmd = ENABLE;

    PLIC_Init(&PLIC_InitStructure);

}

b) CAN

**void** User_CANFD3_Init()

{

    CANFD3_CLK_ENABLE();

    GPIOC_CLK_ENABLE();

    

    GPIO_InitTypeDef  GPIO_InitStructure;

    CANFD_InitTypeDef CANFD_InitStructure;

    PLIC_InitTypeDef  PLIC_InitStructure;

 

    /* Set GPIO multiplex mapping */

    GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_CAN3);

    GPIO_PinAFConfig(GPIOC, GPIO_PinSource8, GPIO_AF_CAN3);

 

    /* GPIO Configure */

    GPIO_StructInit(&GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

    GPIO_InitStructure.GPIO_OType = GPIO_Out_PP;

    GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_18mA;

     

    GPIO_Init(GPIOC, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;

    GPIO_InitStructure.GPIO_IType = GPIO_IPU;

    GPIO_InitStructure.GPIO_OStrength = GPIO_OStrength_18mA;

    GPIO_Init(GPIOC, &GPIO_InitStructure);

     

    /* Initializes the CANFD1 */

    /* Arbitration Phase (Nominal) Baud Rate 500KHz */

    /* Data Phase Baud Rate 2MHz */

    CANFD_StructInit(&CANFD_InitStructure);

    CANFD_InitStructure.CANFD_SRR = CANFD_SRR_RESET;

    CANFD_InitStructure.CANFD_APBRPR = CANFD_APBRPR_10tp;

    CANFD_InitStructure.CANFD_APBTR_APTS1 = CANFD_APBTR_TS1_11tp;

    CANFD_InitStructure.CANFD_APBTR_APTS2 = CANFD_APBTR_TS2_4tp;

    CANFD_InitStructure.CANFD_APBTR_APSJW = CANFD_APBTR_SJW_2tp;

     

    CANFD_InitStructure.CANFD_DPBRPR = CANFD_DPBRPR_2tp;

    CANFD_InitStructure.CANFD_DPBTR_DPTS1 = CANFD_DPBTR_TS1_7tp;

    CANFD_InitStructure.CANFD_DPBTR_DPTS2 = CANFD_DPBTR_TS2_2tp;

    CANFD_InitStructure.CANFD_DPBTR_DPSJW = CANFD_DPBTR_SJW_2tp;

    CANFD_Init(CANFD3, &CANFD_InitStructure);

         

    /* CANFD receive filter configure */

    CANFD_FilterInit(CANFD3, TB0, 0xFFE00000, 0X62E00000);        

 

    CANFD_AutoRetransConfig(CANFD3,ENABLE);

    /* Enable new message received interrupt */

    CANFD_ITConfig(CANFD3, CANFD_IT_ERXOK, ENABLE);

    /* CANFD Enable */

    CANFD_Enable(CANFD3);

     

    PLIC_StructInit(&PLIC_InitStructure);

 

    /* Configer the CANFD1 interrupt */

    PLIC_InitStructure.PLIC_IRQChannel = CANFD3_IRQn;

    PLIC_InitStructure.PLIC_IRQPriority = 2;

    PLIC_InitStructure.PLIC_IRQChannelCmd = ENABLE;

    PLIC_Init(&PLIC_InitStructure);

    CANFD_ClearITPendingBit(CANFD3, CANFD_CLEAR_ALL);

}

通過遵循"參數(shù)配置在先，外設(shè)使能在后"的原則，并采用結(jié)構(gòu)化初始化流程，可以顯著提高M(jìn)CU系統(tǒng)的穩(wěn)定性和可靠性。

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