STM32_GPIO configuration and library function explanation - LED marquee

v GPIO_ResetBits writes 0 to the specified Pin of the specified Port:

void GPIO_ResetBits(GPIO_TypeDef* GPIOx, u16 GPIO_Pin)
{
/* Check the parameters */
assert_param(IS_GPIO_ALL_PERIPH(GPIOx));
assert_param(IS_GPIO_PIN(GPIO_Pin));

GPIOx->BRR = GPIO_Pin;
}

/* Includes ----------------------------------------------- ------------------*/
#include "stm32f10x_lib.h"

/* Private function prototypes ------------------ ----------------------------------*/
void RCC_Configuration(void);
void NVIC_Configuration(void);
void GPIO_Configuration(void);
void Delay(vu32 nCount);

/****************************************** *************************************
* Function Name: main
* Description: Main program.
* Input : None
* Return : None
********************************************** *************************************/
int main(void)
{
#ifdef DEBUG
debug();
# endif

/* Configure the system clocks */
RCC_Configuration();

/* NVIC Configuration */
NVIC_Configuration();

/* Configure the GPIO ports */
GPIO_Configuration();

/* Infinite loop */
while (1)
{
GPIO_SetBits(GPIOC,GPIO_Pin_6);//Turn on LED1
Delay(1000000);
Delay(1000000);//Turn on for a while so that people can see the exact change of the LED
GPIO_ResetBits(GPIOC,GPIO_Pin_6);//Turn off LED1

GPIO_SetBits(GPIOC,GPIO_Pin_7);//Turn on LED2
Delay(1000000);
Delay(1000000);
GPIO_ResetBits(GPIOC,GPIO_Pin_7);//Turn off LED2

GPIO_SetBits(GPIOC,GPIO_Pin_8);//Turn on LED3
Delay(1000000);
Delay(1000000);
GPIO_ResetBits(GPIOC,GPIO_Pin_8); //Turn off LED3

GPIO_SetBits(GPIOC,GPIO_Pin_9);//Light up LED4
Delay(1000000);
Delay(1000000);
GPIO_ResetBits(GPIOC,GPIO_Pin_9);//Turn off LED4
}
}

/************** *************************************************** ***************
* Function Name : RCC_Configuration
* Description : Configures the different system clocks.
* Input : None
* Return : None
************* *************************************************** ****************/
void RCC_Configuration(void)
{
ErrorStatus HSEStartUpStatus;

/* RCC system reset(for debug purpose) */
RCC_DeInit();

/* Enable HSE */
RCC_HSEConfig( RCC_HSE_ON);

/* Wait till HSE is ready */
HSEStartUpStatus = RCC_WaitForHSEStartUp();

if (HSEStartUpStatus == SUCCESS)
{
/* Enable Prefetch Buffer */
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

/* Flash 2 wait state */
FLASH_SetLatency(FLASH_Latency_2);

/* HCLK = SYSCLK */
RCC_HCLKConfig(RCC_SYSCLK_ Div1);

/ * PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1);

/* PCLK1 = HCLK/2 */
RCC_PCLK1Config(RCC_HCLK_Div2);

/* PLLCLK = 8MHz * 9 = 72 MHz */
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);

/* Enable PLL */
RCC_PLLCmd(ENABLE);

/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET) {}

/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08) {}
}

/* Enable GPIOC clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
}

/********************************************** ******************************************
* Function Name: NVIC_Configuration
* Description: Configures Vector Table base location.
* Input : None
* Return : None
**************************************** ***************************************/
void NVIC_Configuration(void)
{
#ifdef VECT_TAB_RAM
/ * Set the Vector Table base location at 0x20000000 */
NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);
#else /* VECT_TAB_FLASH */
/* Set the Vector Table base location at 0x08000000 */
NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
#endif
}

/****************************************************** ****************************
* Function Name : GPIO_Configuration
* Description : Configures the different GPIO ports.
* Input : None
* Return : None
************************************************ *******************************/
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;

/* Configure PC.06, PC. 07, PC.08 and PC.09 as Output push-pull */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9;
GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_Init(GPIOC, &GPIO_InitStructure);
}

/********************************************** ******************************************
* Function Name: Delay
* Description: Inserts a delay time .
* Input : nCount: specifies the delay time length.
* Return : None
********************************** *********************************************/
void Delay(vu32 nCount)
{
for(; nCount != 0; nCount--);
}

#ifdef DEBUG
/****************************** ***************************************************
* Function Name: assert_failed
* Description: Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* Input: - file: pointer to the source file name
* - line: assert_param error line source number
* Return: None
** *************************************************** ***************************/
void assert_failed(u8* file, u32 line)
{
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

/* Infinite loop */
while (1)
{
}
}
#endif

How to debug: Set a breakpoint at while (1).

After executing the GPIO_Configuration function, observe the GPIO_CRL and GPIO_CRH registers and you can see:

The mode configuration of each pin is determined by 4 bits in GPIO_CRL or GPIO_CRH. For example, the PC6 pin is determined by the MODE6[1:0] and CNF6[1:0] bits in GPIO_CRL, and the others are determined by analogy.

The GPIO_CRL register is involved, as shown below

 

 

Because MODE6[1:0]=11, looking at the above table, it can be concluded that PC6 is in output mode and the maximum speed is 50MHZ. Since CNF6[1:0]=00 and in output mode, the output driver is used in general push-pull output mode.

 

After executing GPIO_SetBits(GPIOC,GPIO_Pin_6); //Turn on LED1, you can see: GPIO_ODR's ODR6=1

After executing GPIO_ResetBits(GPIOC,GPIO_Pin_6); //Turn off LED1, you can see: GPIO_ODR's ODR6=0

The same goes for other pins.