STM32 single chip microcomputer - bit band operation

One 、 Bit band operation

One 、 Bit band operation
1. significance
Think back to writing 51 Code

P0 = 0x10;     // take P0 Port set to 0x10
P1_0=1;        // take P1 port 0 Pin No. 1 is set to high level 
a = P2_2;      // obtain P2 port 2 The level of pin No 

According to the above method , We can find that fast positioning can modify the level of a pin and obtain the status of the pin
2. reason
GPIO_SetBits、GPIO_ResetBits operation IO The performance of the mouth has not reached the extreme , Because these functions require on-site protection and on-site recovery , It takes time , Not one step in place , Using bit band operation does not have the above trouble , Simple and fast ！

 Example 1：
GPIO_SetBits(GPIOF,GPIO_Pin_9);
 It is amended as follows 
PFout(9)=1;

 Example 2： 
GPIO_ResetBits(GPIOF,GPIO_Pin_9);
 It is amended as follows 
PFout(9)=0;

Because it is used to set the level or read the level of the pin , Library function efficiency is not high , It's hard to cope with high-performance occasions , The following code , To modify the level of a pin, at least 3 Line code , It also does not include the implicit calling function and the return process of the function .

void GPIO_SetBits(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin)
{
    
  /* Check the parameters */
  assert_param(IS_GPIO_ALL_PERIPH(GPIOx));
  assert_param(IS_GPIO_PIN(GPIO_Pin));

  GPIOx->BSRRL = GPIO_Pin;
}

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3. The formula
About IO The access address corresponding to the pin , You can refer to the following formula

 The bits of the register are aliased  = 0x42000000 + （ The address of the register -0x40000000）*32 +  Pin number *4

Two 、 Register address and alias address translation skills

1. Determine the starting address of a port , Such as port F The starting address of access is GPIOF_BASE

#define GPIOF ((GPIO_TypeDef *) GPIOF_BASE)

typedef struct
{
    
  __IO uint32_t MODER;    /*!< GPIO port mode register, Address offset: 0x00 */
  __IO uint32_t OTYPER;   /*!< GPIO port output type register, Address offset: 0x04 */
  __IO uint32_t OSPEEDR;  /*!< GPIO port output speed register, Address offset: 0x08 */
  __IO uint32_t PUPDR;    /*!< GPIO port pull-up/pull-down register, Address offset: 0x0C */
  __IO uint32_t IDR;      /*!< GPIO port input data register, Address offset: 0x10 */
  __IO uint32_t ODR;      /*!< GPIO port output data register, Address offset: 0x14 */
  __IO uint16_t BSRRL;    /*!< GPIO port bit set/reset low register, Address offset: 0x18 */
  __IO uint16_t BSRRH;    /*!< GPIO port bit set/reset high register, Address offset: 0x1A */
  __IO uint32_t LCKR;     /*!< GPIO port configuration lock register, Address offset: 0x1C */
  __IO uint32_t AFR[2];   /*!< GPIO alternate function registers, Address offset: 0x20-0x24 */
} GPIO_TypeDef;

2. Calculate the offset value according to the register address to be accessed , Such as calculation

GPIOF Of ODR Register address  = GPIOF_BASE+0x14;

3. Convert according to the following formula

 The bits of the register are aliased  = 0x42000000 + （ The address of the register -0x40000000）*8*4 +  Pin number *4

The detailed schematic diagram is shown below ：

4. Set up PF9 The pin level code is as follows

uint32_t *PF9_BitBand = (uint32_t *)(0x42000000 + (GPIOF_BASE + 0x14 - 0x40000000)*32 + 9*4);

Better solution method ：

uint32_t *PF9_BitBand   = (uint32_t *)(0x42000000 + ((uint32_t)&GPIOF->ODR - 0x40000000)*32 + 9*4);	

3、 ... and 、 Bit band operation LED Lamp example

#include "stdio.h"
#include "stm32f10x.h"
#define PAout(n) *((uint32_t *)(0x42000000 + ((uint32_t)&GPIOA->ODR - 0x40000000)*32 + n*4))
//#define PAout(x) *((uint32_t *)(0x42000000 + (((uint32_t)&GPIOA->ODR) - 0x40000000)*32 + x*4))
void delay(int len)  // The time delay function 
{
    
	volatile unsigned int i = 6*1000*len;
	while(i--);
}



int main(void){
    
	GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);   //  Enable port A The clock of 

    /* LED I/O To configure  */    
	GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_3;    //1 and 3 Pin 
    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_Out_PP;     //  General push-pull output 
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;      // 2MHz
    GPIO_Init(GPIOA, &GPIO_InitStructure);
	
	
    /*  Close all after configuration LED */
	GPIO_SetBits(GPIOA,GPIO_Pin_1);
	
	while(1)
	{
    
		PAout(3) = 0;
		delay(200);
		PAout(3) = 1;
		delay(200);
	}	
}

proteus Simulation