00. 目錄

文章目錄

• • 00. 目錄
  • 01. GPIO復用概述
  • 02. 寄存器描述
  • 03. 類型
  • 04. 函數
  • 05. 參考示例
  • 06. 附錄
  • 07. 聲明

01. GPIO復用概述

STM32F4 有很多的內置外設，這些外設的外部引腳都是與 GPIO 復用的。也就是說，一個 GPIO如果可以復用為內置外設的功能引腳，那么當這個 GPIO 作為內置外設使用的時候，就叫做復用。

STM32F4 系列微控制器 IO 引腳通過一個復用器連接到內置外設或模塊。該復用器一次只允許一個外設的復用功能（AF）連接到對應的 IO 口。這樣可以確保共用同一個 IO 引腳的外設之間不會發生沖突。

每個 IO 引腳都有一個復用器，該復用器采用 16 路復用功能輸入（AF0 到 AF15），可通過GPIOx_AFRL(針對引腳 0-7)和 GPIOx_AFRH（針對引腳 8-15）寄存器對這些輸入進行配置，每四位控制一路復用

1）完成復位后，所有 IO 都會連接到系統的復用功能 0（AF0）。
2）外設的復用功能映射到 AF1 到 AF13。
3）Cortex-M4 EVENTOUT 映射到 AF15。

02. 寄存器描述

探索者 STM32F407 開發板的原理圖上 PC11 的原理圖如圖 所示：

PC11 可以作為 SPI3_MISO/U3_RX/U4_RX/SDIO_D3/DCMI_D4/I2S3ext_SD等復用功能輸出，這么多復用功能，如果這些外設都開啟了，那么對 STM32F1 來說，那就可能亂套了，外設之間可互相干擾，但是 STM32F4，由于有復用功能選擇功能，可以讓 PC11 僅連接到某個特定的外設，因此不存在互相干擾的情況。

GPIO 復用功能低位寄存器 (GPIOx_AFRL) (x = A…I)
GPIO alternate function low register
偏移地址：0x20
復位值：0x0000 0000

GPIO 復用功能高位寄存器 (GPIOx_AFRH) (x = A…I)
GPIO alternate function high register
偏移地址：0x24
復位值：0x0000 0000

在微控制器完成復位后，所有 IO 口都會連接到系統復用功能 0（AF0）。這里大家需要注意，對于系統復用功能 AF0，我們將 IO 口連接到 AF0 之后，還要根據所用功能進行配置：

JTAG/SWD:在器件復位之后，會將這些功能引腳指定為專用引腳。也就是說，這些引腳在復位后默認就是 JTAG/SWD 功能。如果我們要作為 GPIO 來使用，就需要對對應的 IO口復用器進行配置。

RTC_REFIN:此引腳在系統復位之后要使用的話要配置為浮空輸入模式。

MCO1 和 MCO2：這些引腳在系統復位之后要使用的話要配置為復用功能模式。

03. 類型

復用功能相關宏

/** * @brief AF 0 selection */ #define GPIO_AF_RTC_50Hz ((uint8_t)0x00) /* RTC_50Hz Alternate Function mapping */ #define GPIO_AF_MCO ((uint8_t)0x00) /* MCO (MCO1 and MCO2) Alternate Function mapping */ #define GPIO_AF_TAMPER ((uint8_t)0x00) /* TAMPER (TAMPER_1 and TAMPER_2) Alternate Function mapping */ #define GPIO_AF_SWJ ((uint8_t)0x00) /* SWJ (SWD and JTAG) Alternate Function mapping */ #define GPIO_AF_TRACE ((uint8_t)0x00) /* TRACE Alternate Function mapping */ #if defined(STM32F446xx) #define GPIO_AF0_TIM2 ((uint8_t)0x00) /* TIM2 Alternate Function mapping */ #endif /* STM32F446xx *//** * @brief AF 1 selection */ #define GPIO_AF_TIM1 ((uint8_t)0x01) /* TIM1 Alternate Function mapping */ #define GPIO_AF_TIM2 ((uint8_t)0x01) /* TIM2 Alternate Function mapping */ #if defined(STM32F410xx) || defined(STM32F413_423xx) #define GPIO_AF_LPTIM ((uint8_t)0x01) /* LPTIM Alternate Function mapping */ #endif /* STM32F410xx || STM32F413_423xx */ /** * @brief AF 2 selection */ #define GPIO_AF_TIM3 ((uint8_t)0x02) /* TIM3 Alternate Function mapping */ #define GPIO_AF_TIM4 ((uint8_t)0x02) /* TIM4 Alternate Function mapping */ #define GPIO_AF_TIM5 ((uint8_t)0x02) /* TIM5 Alternate Function mapping *//** * @brief AF 3 selection */ #define GPIO_AF_TIM8 ((uint8_t)0x03) /* TIM8 Alternate Function mapping */ #define GPIO_AF_TIM9 ((uint8_t)0x03) /* TIM9 Alternate Function mapping */ #define GPIO_AF_TIM10 ((uint8_t)0x03) /* TIM10 Alternate Function mapping */ #define GPIO_AF_TIM11 ((uint8_t)0x03) /* TIM11 Alternate Function mapping */ #if defined(STM32F446xx) #define GPIO_AF3_CEC ((uint8_t)0x03) /* CEC Alternate Function mapping */ #endif /* STM32F446xx */ #if defined(STM32F413_423xx) #define GPIO_AF3_DFSDM2 ((uint8_t)0x03) /* DFSDM2 Alternate Function mapping */ #endif /* STM32F413_423xx */ /** * @brief AF 4 selection */ #define GPIO_AF_I2C1 ((uint8_t)0x04) /* I2C1 Alternate Function mapping */ #define GPIO_AF_I2C2 ((uint8_t)0x04) /* I2C2 Alternate Function mapping */ #define GPIO_AF_I2C3 ((uint8_t)0x04) /* I2C3 Alternate Function mapping */ #if defined(STM32F446xx) #define GPIO_AF4_CEC ((uint8_t)0x04) /* CEC Alternate Function mapping */ #endif /* STM32F446xx */ #if defined(STM32F410xx) || defined(STM32F412xG) || defined(STM32F413_423xx) || defined(STM32F446xx) #define GPIO_AF_FMPI2C ((uint8_t)0x04) /* FMPI2C Alternate Function mapping */ #endif /* STM32F410xx || STM32F446xx *//** * @brief AF 5 selection */ #define GPIO_AF_SPI1 ((uint8_t)0x05) /* SPI1/I2S1 Alternate Function mapping */ #define GPIO_AF_SPI2 ((uint8_t)0x05) /* SPI2/I2S2 Alternate Function mapping */ #define GPIO_AF5_SPI3 ((uint8_t)0x05) /* SPI3/I2S3 Alternate Function mapping (Only for STM32F411xE and STM32F413_423xx Devices) */ #define GPIO_AF_SPI4 ((uint8_t)0x05) /* SPI4/I2S4 Alternate Function mapping */ #define GPIO_AF_SPI5 ((uint8_t)0x05) /* SPI5 Alternate Function mapping */ #define GPIO_AF_SPI6 ((uint8_t)0x05) /* SPI6 Alternate Function mapping *//** * @brief AF 6 selection */ #define GPIO_AF_SPI3 ((uint8_t)0x06) /* SPI3/I2S3 Alternate Function mapping */ #define GPIO_AF6_SPI1 ((uint8_t)0x06) /* SPI1 Alternate Function mapping (Only for STM32F410xx Devices) */ #define GPIO_AF6_SPI2 ((uint8_t)0x06) /* SPI2 Alternate Function mapping (Only for STM32F410xx/STM32F411xE Devices) */ #define GPIO_AF6_SPI4 ((uint8_t)0x06) /* SPI4 Alternate Function mapping (Only for STM32F411xE Devices) */ #define GPIO_AF6_SPI5 ((uint8_t)0x06) /* SPI5 Alternate Function mapping (Only for STM32F410xx/STM32F411xE Devices) */ #define GPIO_AF_SAI1 ((uint8_t)0x06) /* SAI1 Alternate Function mapping */ #define GPIO_AF_I2S2ext ((uint8_t)0x06) /* I2S2ext_SD Alternate Function mapping (only for STM32F412xG and STM32F413_423xx Devices) */ #if defined(STM32F412xG) || defined(STM32F413_423xx) #define GPIO_AF6_DFSDM1 ((uint8_t)0x06) /* DFSDM1 Alternate Function mapping */ #endif /* STM32F412xG || STM32F413_423xx */ #if defined(STM32F413_423xx) #define GPIO_AF6_DFSDM2 ((uint8_t)0x06) /* DFSDM2 Alternate Function mapping */ #endif /* STM32F413_423xx *//** * @brief AF 7 selection */ #define GPIO_AF_USART1 ((uint8_t)0x07) /* USART1 Alternate Function mapping */ #define GPIO_AF_USART2 ((uint8_t)0x07) /* USART2 Alternate Function mapping */ #define GPIO_AF_USART3 ((uint8_t)0x07) /* USART3 Alternate Function mapping */ #define GPIO_AF7_SPI3 ((uint8_t)0x07) /* SPI3/I2S3ext Alternate Function mapping */ #if defined(STM32F413_423xx) #define GPIO_AF7_DFSDM2 ((uint8_t)0x07) /* DFSDM2 Alternate Function mapping */ #define GPIO_AF7_SAI1 ((uint8_t)0x07) /* SAI1 Alternate Function mapping */ #endif /* STM32F413_423xx *//** * @brief AF 7 selection Legacy */ #define GPIO_AF_I2S3ext GPIO_AF7_SPI3/** * @brief AF 8 selection */ #define GPIO_AF_UART4 ((uint8_t)0x08) /* UART4 Alternate Function mapping */ #define GPIO_AF_UART5 ((uint8_t)0x08) /* UART5 Alternate Function mapping */ #define GPIO_AF_USART6 ((uint8_t)0x08) /* USART6 Alternate Function mapping */ #define GPIO_AF_UART7 ((uint8_t)0x08) /* UART7 Alternate Function mapping */ #define GPIO_AF_UART8 ((uint8_t)0x08) /* UART8 Alternate Function mapping */ #if defined(STM32F412xG) || defined(STM32F413_423xx) #define GPIO_AF8_USART3 ((uint8_t)0x08) /* USART3 Alternate Function mapping */ #define GPIO_AF8_DFSDM1 ((uint8_t)0x08) /* DFSDM Alternate Function mapping */ #define GPIO_AF8_CAN1 ((uint8_t)0x08) /* CAN1 Alternate Function mapping */ #endif /* STM32F412xG || STM32F413_423xx */ #if defined(STM32F446xx) #define GPIO_AF8_SAI2 ((uint8_t)0x08) /* SAI2 Alternate Function mapping */ #define GPIO_AF_SPDIF ((uint8_t)0x08) /* SPDIF Alternate Function mapping */ #endif /* STM32F446xx *//** * @brief AF 9 selection */ #define GPIO_AF_CAN1 ((uint8_t)0x09) /* CAN1 Alternate Function mapping */ #define GPIO_AF_CAN2 ((uint8_t)0x09) /* CAN2 Alternate Function mapping */ #define GPIO_AF_TIM12 ((uint8_t)0x09) /* TIM12 Alternate Function mapping */ #define GPIO_AF_TIM13 ((uint8_t)0x09) /* TIM13 Alternate Function mapping */ #define GPIO_AF_TIM14 ((uint8_t)0x09) /* TIM14 Alternate Function mapping */ #define GPIO_AF9_I2C2 ((uint8_t)0x09) /* I2C2 Alternate Function mapping (Only for STM32F401xx/STM32F410xx/STM32F411xE/STM32F412xG/STM32F413_423xx Devices) */ #define GPIO_AF9_I2C3 ((uint8_t)0x09) /* I2C3 Alternate Function mapping (Only for STM32F401xx/STM32F411xE/STM32F412xG and STM32F413_423xx Devices) */ #if defined(STM32F446xx) #define GPIO_AF9_SAI2 ((uint8_t)0x09) /* SAI2 Alternate Function mapping */ #endif /* STM32F446xx */ #define GPIO_AF9_LTDC ((uint8_t)0x09) /* LTDC Alternate Function mapping */ #if defined(STM32F412xG) || defined(STM32F413_423xx) || defined(STM32F446xx) || defined(STM32F469_479xx) #define GPIO_AF9_QUADSPI ((uint8_t)0x09) /* QuadSPI Alternate Function mapping */ #endif /* STM32F412xG || STM32F413_423xx || STM32F446xx || STM32F469_479xx */ #if defined(STM32F410xx) || defined(STM32F412xG) || defined(STM32F413_423xx) #define GPIO_AF9_FMPI2C ((uint8_t)0x09) /* FMPI2C Alternate Function mapping (Only for STM32F410xx Devices) */ #endif /* STM32F410xx || STM32F412xG || STM32F413_423xx *//** * @brief AF 10 selection */ #define GPIO_AF_OTG_FS ((uint8_t)0xA) /* OTG_FS Alternate Function mapping */ #define GPIO_AF_OTG_HS ((uint8_t)0xA) /* OTG_HS Alternate Function mapping */ #if defined(STM32F446xx) #define GPIO_AF10_SAI2 ((uint8_t)0x0A) /* SAI2 Alternate Function mapping */ #endif /* STM32F446xx */ #if defined(STM32F412xG) || defined(STM32F413_423xx) || defined(STM32F446xx) || defined(STM32F469_479xx) #define GPIO_AF10_QUADSPI ((uint8_t)0x0A) /* QuadSPI Alternate Function mapping */ #endif /* STM32F412xG || STM32F413_423xx || STM32F446xx || STM32F469_479xx */ #if defined(STM32F412xG) || defined(STM32F413_423xx) #define GPIO_AF10_FMC ((uint8_t)0xA) /* FMC Alternate Function mapping */ #define GPIO_AF10_DFSDM1 ((uint8_t)0xA) /* DFSDM Alternate Function mapping */ #endif /* STM32F412xG || STM32F413_423xx */ #if defined(STM32F413_423xx) #define GPIO_AF10_DFSDM2 ((uint8_t)0x0A) /* DFSDM2 Alternate Function mapping */ #define GPIO_AF10_SAI1 ((uint8_t)0x0A) /* SAI1 Alternate Function mapping */ #endif /* STM32F413_423xx */ /** * @brief AF 11 selection */ #define GPIO_AF_ETH ((uint8_t)0x0B) /* ETHERNET Alternate Function mapping */ #if defined(STM32F413_423xx) #define GPIO_AF11_UART4 ((uint8_t)0x0B) /* UART4 Alternate Function mapping */ #define GPIO_AF11_UART5 ((uint8_t)0x0B) /* UART5 Alternate Function mapping */ #define GPIO_AF11_UART9 ((uint8_t)0x0B) /* UART9 Alternate Function mapping */ #define GPIO_AF11_UART10 ((uint8_t)0x0B) /* UART10 Alternate Function mapping */ #define GPIO_AF11_CAN3 ((uint8_t)0x0B) /* CAN3 Alternate Function mapping */ #endif /* STM32F413_423xx *//** * @brief AF 12 selection */ #if defined(STM32F40_41xxx) || defined(STM32F412xG) || defined(STM32F413_423xx) #define GPIO_AF_FSMC ((uint8_t)0xC) /* FSMC Alternate Function mapping */ #endif /* STM32F40_41xxx || STM32F412xG || STM32F413_423xx */#if defined(STM32F427_437xx) || defined(STM32F429_439xx) || defined(STM32F446xx) || defined(STM32F469_479xx) #define GPIO_AF_FMC ((uint8_t)0xC) /* FMC Alternate Function mapping */ #endif /* STM32F427_437xx || STM32F429_439xx || STM32F446xx || STM32F469_479xx */#define GPIO_AF_OTG_HS_FS ((uint8_t)0xC) /* OTG HS configured in FS, Alternate Function mapping */ #define GPIO_AF_SDIO ((uint8_t)0xC) /* SDIO Alternate Function mapping *//** * @brief AF 13 selection */ #define GPIO_AF_DCMI ((uint8_t)0x0D) /* DCMI Alternate Function mapping */ #if defined(STM32F469_479xx) #define GPIO_AF_DSI ((uint8_t)0x0D) /* DSI Alternate Function mapping */ #endif /* STM32F469_479xx */ /** * @brief AF 14 selection */ #define GPIO_AF_LTDC ((uint8_t)0x0E) /* LCD-TFT Alternate Function mapping */ #if defined(STM32F413_423xx) #define GPIO_AF14_RNG ((uint8_t)0x0E) /* RNG Alternate Function mapping */ #endif /* STM32F413_423xx *//** * @brief AF 15 selection */ #define GPIO_AF_EVENTOUT ((uint8_t)0x0F) /* EVENTOUT Alternate Function mapping */#define IS_GPIO_AF(AF) (((AF) == GPIO_AF_RTC_50Hz) || ((AF) == GPIO_AF_TIM14) || \((AF) == GPIO_AF_MCO) || ((AF) == GPIO_AF_TAMPER) || \((AF) == GPIO_AF_SWJ) || ((AF) == GPIO_AF_TRACE) || \((AF) == GPIO_AF_TIM1) || ((AF) == GPIO_AF_TIM2) || \((AF) == GPIO_AF_TIM3) || ((AF) == GPIO_AF_TIM4) || \((AF) == GPIO_AF_TIM5) || ((AF) == GPIO_AF_TIM8) || \((AF) == GPIO_AF_I2C1) || ((AF) == GPIO_AF_I2C2) || \((AF) == GPIO_AF_I2C3) || ((AF) == GPIO_AF_SPI1) || \((AF) == GPIO_AF_SPI2) || ((AF) == GPIO_AF_TIM13) || \((AF) == GPIO_AF_SPI3) || ((AF) == GPIO_AF_TIM14) || \((AF) == GPIO_AF_USART1) || ((AF) == GPIO_AF_USART2) || \((AF) == GPIO_AF_USART3) || ((AF) == GPIO_AF_UART4) || \((AF) == GPIO_AF_UART5) || ((AF) == GPIO_AF_USART6) || \((AF) == GPIO_AF_CAN1) || ((AF) == GPIO_AF_CAN2) || \((AF) == GPIO_AF_OTG_FS) || ((AF) == GPIO_AF_OTG_HS) || \((AF) == GPIO_AF_ETH) || ((AF) == GPIO_AF_OTG_HS_FS) || \((AF) == GPIO_AF_SDIO) || ((AF) == GPIO_AF_DCMI) || \((AF) == GPIO_AF_EVENTOUT) || ((AF) == GPIO_AF_FSMC)) #endif /* STM32F40_41xxx */

04. 函數

GPIO復用功能函數

/* GPIO Alternate functions configuration function ****************************/ void GPIO_PinAFConfig(GPIO_TypeDef* GPIOx, uint16_t GPIO_PinSource, uint8_t GPIO_AF);

05. 參考示例

串口配置

/*GPIOA9 與 GPIOA10 初始化*/ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;// 復用功能 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;//速度 50MHz GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //推挽復用輸出 GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //上拉 GPIO_Init(GPIOA,&GPIO_InitStructure); //初始化 PA9，PA10/*PA9 連接 AF7，復用為 USART1_TX */ GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_USART1); /* PA10 連接 AF7,復用為 USART1_RX*/ GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_USART1);

06. 附錄

6.1 【STM32】STM32系列教程匯總

網址：【STM32】STM32系列教程匯總

07. 聲明

該教程參考了正點原子的《STM32 F4 開發指南》

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