Light a light with stm32

One 、 Preface

Single chip model ：STM32F103C8T6
development environment ：Keil5

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Two 、 analysis

Want to control LED The lamp , Of course, through control STM32 Chip I/O Pin level to achieve . stay STM32 On chip ,I/O The pins can be set to various functions by software , Such as input or output , therefore I/O Pins are also called GPIO; On the chip GPIO Usually grouped , for example GPIOA、GPIOB、GPIOC wait .

therefore , control LED The steps of can be roughly divided into the following steps ：

• GPIO There are many port pins ----- It is necessary to select the specific pin to be controlled ;
• GPIO So rich in functions ----- You need to configure specific functions ;
• control LED On and off of ----- Set up GPIO The output voltage ;

Reference resources 《STM32 Reference manual 》, as follows ：

GPIO The functions of registers are briefly summarized as follows ：

• Configuration register ： selected GPIO Specific functions , The most basic, such as choosing as input or output port ;
• Data register ： Save the GPIO The input level of or the level to be output ;
• Bit control register ： Set the data of a pin to 1 or 0, Control the level of the output ;
• Lock register ： After setting a locking pin , You cannot modify its configuration ;

But we use library development , Basically, it will not be controlled by directly operating registers GPIO,《stm32f10x.h》 This document puts STM32 All registers of are address mapped , for example ：

GPIOC_BASE representative GPIOC Base address of group register

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3、 ... and 、 Write code

Use peripherals , Be sure to turn on the peripheral clock ;

1、 establish led file , establish led.c and led.h stay USER Under the folder

2、 Add code

attachment ： One pin of the small lamp is connected STM32 Upper GPIOC13, One pin is connected STM32 Upper GND
effect ： The small lamp lights up circularly - destroy - bright - destroy

led.h

#ifndef __LED_H
#define __LED_H

#include "stm32f10x.h"

void LED_GPIO_Config(void);

#endif 

led.c

#include "led.h"

void LED_GPIO_Config(void)
{
    
	// Define a GPIO_InitTypeDef Type of structure 
	GPIO_InitTypeDef GPIO_InitStructure;
	
	// Turn on GPIOC The peripheral clock of 
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC,ENABLE);
	
	// Choose what you want to control GPIOC Pin 
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
	
	// Set pin mode ： General push-pull output 
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
	
	// Set pin rate ：50MHz
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	
	// Call library function , initialization GPIOC13
	GPIO_Init(GPIOC,&GPIO_InitStructure);
}

main.c

#include "stm32f10x.h"
#include "led.h"

void Delay(int m,int n);	// The time delay function 

int main(void)
{
    
	LED_GPIO_Config();
	while(1)
	{
    
		// Set up GPIOC13 High level （ Little lights ）
		GPIO_SetBits(GPIOC,GPIO_Pin_13);
		
		// Time delay 
		Delay(2000,500);
		
		// Set up GPIOC13 Low level （ Small lights went out ）
		GPIO_ResetBits(GPIOC,GPIO_Pin_13)
		
		// Time delay 
		Delay(2000,500);
	}
}

void Delay(int m,int n)	// Rough delay function 
{
    
	int i,j;
	for(i=0;i<m;i++) {
    
		for(j=0;j<n;j++);
	}
}

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Four 、 Library interface analysis

1、 Initialize structure -----GPIO_InitTypeDef type

typedef struct
{
    
	uint16_t GPIO_Pin;				// Specify the GPIO Pin 
	GPIOSpeed_TypeDef GPIO_Speed;	// Appoint GPIO The highest frequency that the pin can output 
	GPIOMode_TypeDef GPIO_Mode;		// Appoint GPIO The working state of the pin to be configured 
}GPIO_InitTypeDef;

effect ： The whole structure includes GPIO_Pin、GPIO_Speed、GPIO_Mode Three members , We only need to assign different values to these three members to GPIO Ports are configured differently , And these configurable values , Already by ST The library file of is encapsulated into a well-known enumeration constant , This makes it very easy for us to write code .

GPIO_Pin The value is ：

#define GPIO_Pin_0
#define GPIO_Pin_1
......

GPIO_Speed The value is ：

typedef enum
{
    
	GPIO_Speed_10MHz = 1,		// Enumeration constants , The value is 1, Represents that the maximum output rate is 10MHz
	GPIO_Speed_20MHz,			// Enumerating variables that are not assigned values , Automatic addition 1, This constant value is 2
	GPIO_Speed_50MHz			// Constant value is 3
}GPIOSpeed_TypeDef; 

GPIO_Mode The value is ：

typedef enum
{
    
	GPIO_Mode_AIN = 0x0,				// Analog input mode 
	GPIO_Mode_IN_FLOATING = 0x04,		// Floating input mode 
	GPIO_Mode_IPD = 0x28,				// Drop down input mode 
	GPIO_Mode_IPU = 0x48,				// Pull up input mode 
	GPIO_Mode_Out_OD = 0x14,			// Open drain output mode 
	GPIO_Mode_Out_PP = 0x10,			// Universal push-pull output mode 
	GPIO_Mode_AF_OD = 0x1C,				// Multiplexing function open drain output 
	GPIO_Mode_AF_PP = 0x18				// Reuse function push-pull output 
}GPIOMode_TypeDef;

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2、 Initialize library functions -----GPIO_Init()

void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)

GPIO_InitTypeDef It can be understood as a packaged configuration package ,GPIO_Init() Is the tool that makes this configuration package effective ;

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3、 Turn on the peripheral clock
stay startup_stm32f10x_hd.s In startup file , There is a startup code ：

explain ： When the chip is reset （ Including power on reset ）, Will start running this code , The running process calls SystemInit() function , Enter again C In language “_main” Function execution （ And main Functions are different , This is a C Initialization function of standard library ）, After executing this function , Finally jump to “main” Function entrance , Start running the main program .

in other words , When entering main A function named SystemInit() Function of , This function is defined in system_stm32f10x.c In the document , Its function is to set the system clock SYSCLK.

3.5 Version of the library calls... In the startup file SystemInit(), So you don't have to main() Function again . But if you use 3.0 The version of the library must be in main Call in function SystemInit(), To set the system clock , Because in 3.0 Version of the startup code does not call SystemInit() function .

SYSCLK from SystemInit() The configuration. , and GPIO The clock used PCLK2, We use the default value , Also for the 72MHz. We can use the default value without modifying the frequency divider , But the peripheral clock is off by default . Therefore, the peripheral clock is usually set to on when initializing the peripheral . To turn on and off the peripheral clock, you can use the function ：

RCC_APB2PeriphClockCmd(uint32_t RCC_APB2Periph, FunctionalState NewState)

The first parameter is the mount to be controlled in APB2 Peripheral clock on the bus ; The second parameter is to choose whether to turn the clock on or off （ENABLE or FALSE）;

Mounted on APB2 Peripherals on the ：

• RCC_APB2Periph_AFIO
• RCC_APB2Periph_GPIOA
• RCC_APB2Periph_GPIOB
• RCC_APB2Periph_GPIOC
• RCC_APB2Periph_GPIOD
• RCC_APB2Periph_GPIOE
• RCC_APB2Periph_GPIOF
• RCC_APB2Periph_GPIOG
• RCC_APB2Periph_ADC1
• RCC_APB2Periph_ADC2
• RCC_APB2Periph_TIM1
• RCC_APB2Periph_SPI1
• RCC_APB2Periph_TIM8
• RCC_APB2Periph_USART1
• RCC_APB2Periph_ADC3
• RCC_APB2Periph_TIM15
• RCC_APB2Periph_TIM16
• RCC_APB2Periph_TIM17
• RCC_APB2Periph_TIM9
• RCC_APB2Periph_TIM10
• RCC_APB2Periph_TIM11

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4、 control I/O High output 、 Low level
Control GPIO The level of the pin is high or low , As long as GPIOx_BSRR Write the corresponding bit of the register to the control parameter , Of course ST The library also provides us with such function ：

GPIO_SetBits(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin);		// Output high level 
GPIO_ResetBits(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin);		// Output low level 

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5、 Bit operation

• take char Type variable a Seventh place in （bit6） Zero clearing , Other bits remain the same

a &= ~(1<<6);

 First step  1<<6：1 Move left 6 position ,0000 0001 --> 0100 0000
 The second step  ~(1<<6)： The result of moving left is reversed ,0100 0000 --> 1011 1111
 The third step  a &= ~(1<<6)： Take the inverse result and a Conduct and operate , The seventh place is 0, And operation, this bit must be 0, The rest are 1, Keep the original ;

• take char Type variable a Seventh place in （bit6） Set up 1, Other bits remain the same

a |= (1<<6);

 First step  1<<6：1 Move left 6 position ,0000 0001 --> 0100 0000
 The second step  a |= (1<<6)： The result of moving left and a To carry out or operate , The seventh place is 1, Or the operation bit must be 1, The rest are 0, Keep the original ;

• take char Type variable a Seventh place in （bit6） Take the opposite , Other bits remain the same

a ^= (1<<6);

 First step  1<<6：1 Move left 6 position ,0000 0001 --> 0100 0000
 The second step  a ^= (1<<6)： The result of moving left and a To perform exclusive or operations ;
 The seventh place is 1, If a yes 1, If it is the same, the seventh place becomes 0; If a yes 0, If it is different, the seventh place will become 1;
 The rest are 0, If a yes 1, The difference is still 1; If a yes 0, The same is still 0;