先看代码
// PB5
void LED_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructure; //定义一个GPIO_InitTypeDef类型的结构体
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); //使能PB时钟
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; //选中引脚
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; //推挽输出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //IO口速度为50MHz
GPIO_Init(GPIOB, &GPIO_InitStructure); //根据设定参数初始化GPIOB.5
GPIO_SetBits(GPIOA,GPIO_Pin_8); //PB.5 输出高
}
GPIO_InitTypeDef结构体定义如下，有三个参数
typedef struct
{
uint16_t GPIO_Pin; /*!< Specifies the GPIO pins to be configured.
This parameter can be any value of @ref GPIO_pins_define */
GPIOSpeed_TypeDef GPIO_Speed; /*!< Specifies the speed for the selected pins.
This parameter can be a value of @ref GPIOSpeed_TypeDef */
GPIOMode_TypeDef GPIO_Mode; /*!< Specifies the operating mode for the selected pins.
This parameter can be a value of @ref GPIOMode_TypeDef */
}GPIO_InitTypeDef;
其中第二个参数GPIO_Speed类型如下，是个枚举类型
typedef enum
{
GPIO_Speed_10MHz = 1, //枚举常量，值为1，代表输出速率最高为10MHz
GPIO_Speed_2MHz, //对不赋值的枚举常量，依次自动加1，此常量值为2
GPIO_Speed_50MHz //常量值为3
}GPIOSpeed_TypeDef;
定义了3个枚举常量，即GPIO_Speed_10MHz = 1、GPIO_Speed_2MHz = 2、GPIO_Speed_50MHz = 3
同样，GPIOMode_TypeDef也是一个枚举类型定义符，定义如下
typedef enum
{ GPIO_Mode_AIN = 0x0, //模拟输入模式
GPIO_Mode_IN_FLOATING = 0x04, //浮空输入模式
GPIO_Mode_IPD = 0x28, //下拉输入模式
GPIO_Mode_IPU = 0x48, //上拉输入模式
GPIO_Mode_Out_OD = 0x14, //开漏输出模式
GPIO_Mode_Out_PP = 0x10, //通用推挽输出模式
GPIO_Mode_AF_OD = 0x1C, //复用功能开漏输出
GPIO_Mode_AF_PP = 0x18 //复用功能推挽输出
}GPIOMode_TypeDef;
接下来再看下初始化函数GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)
void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)
{
uint32_t currentmode = 0x00, currentpin = 0x00, pinpos = 0x00, pos = 0x00;
uint32_t tmpreg = 0x00, pinmask = 0x00;
/* Check the parameters */
assert_param(IS_GPIO_ALL_PERIPH(GPIOx));
assert_param(IS_GPIO_MODE(GPIO_InitStruct->GPIO_Mode));
assert_param(IS_GPIO_PIN(GPIO_InitStruct->GPIO_Pin));
/*---------------------------- GPIO Mode Configuration -----------------------*/
currentmode = ((uint32_t)GPIO_InitStruct->GPIO_Mode) & ((uint32_t)0x0F);
if ((((uint32_t)GPIO_InitStruct->GPIO_Mode) & ((uint32_t)0x10)) != 0x00)
{
/* Check the parameters */
assert_param(IS_GPIO_SPEED(GPIO_InitStruct->GPIO_Speed));
/* Output mode */
currentmode |= (uint32_t)GPIO_InitStruct->GPIO_Speed;
}
/*---------------------------- GPIO CRL Configuration ------------------------*/
/* Configure the eight low port pins */
if (((uint32_t)GPIO_InitStruct->GPIO_Pin & ((uint32_t)0x00FF)) != 0x00)
{
tmpreg = GPIOx->CRL;
for (pinpos = 0x00; pinpos < 0x08; pinpos++)
{
pos = ((uint32_t)0x01) << pinpos;
/* Get the port pins position */
currentpin = (GPIO_InitStruct->GPIO_Pin) & pos;
if (currentpin == pos)
{
pos = pinpos << 2;
/* Clear the corresponding low control register bits */
pinmask = ((uint32_t)0x0F) << pos;
tmpreg &= ~pinmask;
/* Write the mode configuration in the corresponding bits */
tmpreg |= (currentmode << pos);
/* Reset the corresponding ODR bit */
if (GPIO_InitStruct->GPIO_Mode == GPIO_Mode_IPD)
{
GPIOx->BRR = (((uint32_t)0x01) << pinpos);
}
else
{
/* Set the corresponding ODR bit */
if (GPIO_InitStruct->GPIO_Mode == GPIO_Mode_IPU)
{
GPIOx->BSRR = (((uint32_t)0x01) << pinpos);
}
}
}
}
GPIOx->CRL = tmpreg;
}
/*---------------------------- GPIO CRH Configuration ------------------------*/
/* Configure the eight high port pins */
if (GPIO_InitStruct->GPIO_Pin > 0x00FF)
{
tmpreg = GPIOx->CRH;
for (pinpos = 0x00; pinpos < 0x08; pinpos++)
{
pos = (((uint32_t)0x01) << (pinpos + 0x08));
/* Get the port pins position */
currentpin = ((GPIO_InitStruct->GPIO_Pin) & pos);
if (currentpin == pos)
{
pos = pinpos << 2;
/* Clear the corresponding high control register bits */
pinmask = ((uint32_t)0x0F) << pos;
tmpreg &= ~pinmask;
/* Write the mode configuration in the corresponding bits */
tmpreg |= (currentmode << pos);
/* Reset the corresponding ODR bit */
if (GPIO_InitStruct->GPIO_Mode == GPIO_Mode_IPD)
{
GPIOx->BRR = (((uint32_t)0x01) << (pinpos + 0x08));
}
/* Set the corresponding ODR bit */
if (GPIO_InitStruct->GPIO_Mode == GPIO_Mode_IPU)
{
GPIOx->BSRR = (((uint32_t)0x01) << (pinpos + 0x08));
}
}
}
GPIOx->CRH = tmpreg;
}
}
再看宏定义assert_param
#ifdef USE_FULL_ASSERT
/**
* @brief The assert_param macro is used for function's parameters check.
* @param expr: If expr is false, it calls assert_failed function which reports
* the name of the source file and the source line number of the call
* that failed. If expr is true, it returns no value.
* @retval None
*/
#define assert_param(expr) ((expr) ? (void)0 : assert_failed((uint8_t *)__FILE__, __LINE__))
/* Exported functions ------------------------------------------------------- */
void assert_failed(uint8_t* file, uint32_t line);
#else
#define assert_param(expr) ((void)0)
#endif /* USE_FULL_ASSERT */
如果定义了宏USE_FULL_ASSERT，宏assert_param就起作用，这时候要补写函数
void assert_failed(uint8_t* file, uint32_t line)，默认是不开启的
#define assert_param(expr) ((expr) ? (void)0 : assert_failed((uint8_t *)__FILE__, __LINE__))
如果expr的表达式值为真，则为(void)0，否则调用函数assert_failed((uint8_t *)__FILE__, __LINE__)
assert_failed函数可参考如下，函数的意思就是，如果参数出错，输出出错的文件名称和行号。
void assert_failed(uint8_t* file, uint32_t line)
{
printf("file %s on line %d\r\n", file, line);
while(1);
}
#define IS_GPIO_ALL_PERIPH(PERIPH) (((PERIPH) == GPIOA) || \
((PERIPH) == GPIOB) || \
((PERIPH) == GPIOC) || \
((PERIPH) == GPIOD) || \
((PERIPH) == GPIOE) || \
((PERIPH) == GPIOF) || \
((PERIPH) == GPIOG))
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