III Chip startup and clock system

Chip startup and clock system

1. Chip start

First stm32 According to the starting method ( Reference manual 2.4 section ) Load the startup code from the startup location into memory , Then start executing the startup code , Generally, the official startup code is enough ---------- xxx.s

Start the work of the code ：

Initialize stack space , Define exception vector table call SystemInit ----------- System initialization Initialize the clock , Adjust the exception vector table perform main ---------- The main function

The chip is going to work , The clock and memory must be initialized ,stm32 Memory usage on chip SRAM, You can use it directly , The clock needs to be initialized ,ARM The chip needs to define the exception vector table , perform C Language code must initialize the stack .

stm32f407 Recommended master clock frequency 168MHz

2. The hardware that generates the original frequency

(1) Crystal oscillator

(2)RC(LC) Oscillating circuit

The original frequency will not be very high , The frequency must be increased before use , Up frequency use PLL( Up frequency ) circuit

CPU General structure of the clock system

3.stm32f407 The original clock

HSI RC -------------- High speed internal oscillation clock 16M HSE OSC ------------- High speed external crystal 4~26M(8M) // The above two clock sources can be directly used as the main clock of the system , It can also be done through PLL As the master clock after frequency rise LSI RC --------------- Low speed internal oscillation clock 32K ----- watchdog LSE OSC -------------- Low speed external crystal 32.768K ----- RTC

stm32f407 Clock tree

PLL The output clock of = PLL Input clock X PLLN / PLLM / PLLP

168M = 8M X 336 / 8 / 2

4. take keil5 The system clock of the project is configured as 168MHz

（1） modify system_stm32f4xx.c Of 254 That's ok

#define PLL_M 8

（2） modify stm32f4xx.h Of 127 That's ok

// This file is a read-only property file , To find the file in the file system , Remove the read-only attribute #define HSE_VALUE ((uint32_t)8000000) /*!< Value of the External oscillator in Hz */

practice ：

Configure the main frequency of the system to 168M

modify PLL, Adjust the main frequency of the system

#define PLL_N 336//168M #define PLL_N 432//216M Overclock #define PLL_N 168//84M Frequency reduction

System bus clock frequency ：

SYSCLK The clock ------------ 168MHz HCLK/AHB Bus ---------- 168MHz APB1 The clock -------------- 42MHz APB2 The clock -------------- 84MHz

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Key driven

1. Look at the schematic

As can be seen from the schematic diagram ：

Release the button -------- Pin high level

Press the key -------- Pin low level

The pin corresponding to the key ：

S1 ----- PA0

S2 ----- PE2

S3 ----- PE3

S4 ----- PE4

How to read the level of the input pin

（1） Read the input data register (IDR) The value of the corresponding bit 1 ----- Input high level 0 ----- Input low level

（2） Bit segment operation PAin(0)==0 ----- Input low level PAin(0)==1 ----- Input high level

（3） Library function uint8_t GPIO_ReadInputDataBit(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin); // Which group and which foot are introduced , Return the level of this pin

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practice ：

Complete the detection program of the other three keys , Separate use register Bit segment Library function judgment

Realize the function ：

Press down S2,D2 bright Press down S3,D3 bright Press down S4,D4 bright

//key.c

#include <stm32f4xx.h>
#include <key.h>
void key_init(void)
{
    GPIO_InitTypeDef GPIO_InitStruct;
    
    //1. Turn on GPIOA The clock of 
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA|RCC_AHB1Periph_GPIOE,ENABLE);
    
    //2.GPIO initialization  PA0
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN;// The input mode 
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;// No up and down 
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0;//PA0
    GPIO_Init(GPIOA,&GPIO_InitStruct);
    
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_2|GPIO_Pin_3|GPIO_Pin_4;//PE2 PE3 PE4
    GPIO_Init(GPIOE,&GPIO_InitStruct);

//main.c

#include <stm32f4xx.h>
#include <led.h>
#include <sys.h>
#include <key.h>

int main()
{
	int key_flag = 0;
	
	// initialization 
	led_init();
	key_init();
	
	while(1){
		if(S1==0){
			// Delay chattering 10ms
			delay(100);
			if(S1==0){
				// Real key events 
				if(key_flag==0){// Press and do not release 
					D1 = ~D1;// Take the opposite 
					key_flag = 1;
				}
			}
		}
		else{
			// Delay chattering 10ms
			delay(100);
			if(S1){
				key_flag = 0;
			}
		}
	}

}

//lcd.c

include <stm32f4xx.h>
#include <led.h>

void delay(unsigned int ms)
{
	int i,j;
	
	for(i=0;i<ms;i++)
		for(j=0;j<5000;j++);
}

void led_init(void)
{
	GPIO_InitTypeDef GPIO_InitStruct;
	
	//1. Turn on GPIOE GPIOF The clock of 
	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE|RCC_AHB1Periph_GPIOF,ENABLE);
	
	//2.GPIO initialization  PF9 PF10 PE13 PE14
	GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;// The output mode 
	GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;// Push pull output 
	GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;// High speed 
	GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;// No up and down 
	GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_10;//PF9 PF10
	GPIO_Init(GPIOF,&GPIO_InitStruct);
	
	GPIO_InitStruct.GPIO_Pin = GPIO_Pin_13|GPIO_Pin_14;//PE13 PE14
	GPIO_Init(GPIOE,&GPIO_InitStruct);
	
	//3.LED Off by default 
	GPIO_SetBits(GPIOF,GPIO_Pin_9|GPIO_Pin_10);
	GPIO_SetBits(GPIOE,GPIO_Pin_13|GPIO_Pin_14);
}

//lcd.h

#ifndef _LED_H_
#define _LED_H_

#define D1 PFout(9)
#define D2 PFout(10)
#define D3 PEout(13)
#define D4 PEout(14)

void delay(unsigned int ms);
void led_init(void);

#endif

//key.h

#ifndef _KEY_H_
#define _KEY_H_

#define S1 PAin(0)
#define S2 PEin(2)
#define S3 PEin(3)
#define S4 PEin(4)

void key_init(void);

#endif

 //sys.h                                                This file is defined by the system

#ifndef __SYS_H_
#define __SYS_H_ 
#include "stm32f4xx.h" 

//IO Port operation macro definition 
#define BITBAND(addr, bitnum) ((addr & 0xF0000000)+0x2000000+((addr &0xFFFFF)<<5)+(bitnum<<2)) 
#define MEM_ADDR(addr)  *((volatile unsigned long  *)(addr)) 
#define BIT_ADDR(addr, bitnum)   MEM_ADDR(BITBAND(addr, bitnum)) 
//IO Port address mapping 
#define GPIOA_ODR_Addr    (GPIOA_BASE+20) //0x40020014
#define GPIOB_ODR_Addr    (GPIOB_BASE+20) //0x40020414 
#define GPIOC_ODR_Addr    (GPIOC_BASE+20) //0x40020814 
#define GPIOD_ODR_Addr    (GPIOD_BASE+20) //0x40020C14 
#define GPIOE_ODR_Addr    (GPIOE_BASE+20) //0x40021014 
#define GPIOF_ODR_Addr    (GPIOF_BASE+20) //0x40021414    20 = 0x14
#define GPIOG_ODR_Addr    (GPIOG_BASE+20) //0x40021814   
#define GPIOH_ODR_Addr    (GPIOH_BASE+20) //0x40021C14    
#define GPIOI_ODR_Addr    (GPIOI_BASE+20) //0x40022014     

#define GPIOA_IDR_Addr    (GPIOA_BASE+16) //0x40020010    16 = 0x10
#define GPIOB_IDR_Addr    (GPIOB_BASE+16) //0x40020410 
#define GPIOC_IDR_Addr    (GPIOC_BASE+16) //0x40020810 
#define GPIOD_IDR_Addr    (GPIOD_BASE+16) //0x40020C10 
#define GPIOE_IDR_Addr    (GPIOE_BASE+16) //0x40021010 
#define GPIOF_IDR_Addr    (GPIOF_BASE+16) //0x40021410 
#define GPIOG_IDR_Addr    (GPIOG_BASE+16) //0x40021810 
#define GPIOH_IDR_Addr    (GPIOH_BASE+16) //0x40021C10 
#define GPIOI_IDR_Addr    (GPIOI_BASE+16) //0x40022010 
 
//IO Mouth operation , Only for single IO mouth !
// Make sure n The value is less than 16!
#define PAout(n)   BIT_ADDR(GPIOA_ODR_Addr,n)  // Output  
#define PAin(n)    BIT_ADDR(GPIOA_IDR_Addr,n)  // Input  

#define PBout(n)   BIT_ADDR(GPIOB_ODR_Addr,n)  // Output  
#define PBin(n)    BIT_ADDR(GPIOB_IDR_Addr,n)  // Input  

#define PCout(n)   BIT_ADDR(GPIOC_ODR_Addr,n)  // Output  
#define PCin(n)    BIT_ADDR(GPIOC_IDR_Addr,n)  // Input  

#define PDout(n)   BIT_ADDR(GPIOD_ODR_Addr,n)  // Output  
#define PDin(n)    BIT_ADDR(GPIOD_IDR_Addr,n)  // Input  

#define PEout(n)   BIT_ADDR(GPIOE_ODR_Addr,n)  // Output  
#define PEin(n)    BIT_ADDR(GPIOE_IDR_Addr,n)  // Input 

#define PFout(n)   BIT_ADDR(GPIOF_ODR_Addr,n)  // Output  
#define PFin(n)    BIT_ADDR(GPIOF_IDR_Addr,n)  // Input 

#define PGout(n)   BIT_ADDR(GPIOG_ODR_Addr,n)  // Output  
#define PGin(n)    BIT_ADDR(GPIOG_IDR_Addr,n)  // Input 

#define PHout(n)   BIT_ADDR(GPIOH_ODR_Addr,n)  // Output  
#define PHin(n)    BIT_ADDR(GPIOH_IDR_Addr,n)  // Input 

#define PIout(n)   BIT_ADDR(GPIOI_ODR_Addr,n)  // Output  
#define PIin(n)    BIT_ADDR(GPIOI_IDR_Addr,n)  // Input 


#endif

3. Press the key to shake off ———— Delay chattering

The above key pressing procedures do not matter whether there is a key pressing event , Will occupy CPU To judge , This method is called polling , Low efficiency ,CPU Provides a more efficient way --------- interrupt .