II Stm32f407 chip GPIO programming, register operation, library function operation and bit segment operation

 Stm32f407 chip GPIO Programming

GPIO It's called general input and output interface , As a general input and output function , Input and output 0 and 1, In high level 1, Low level means 0. stay ARM in , The high level is 3.3v, The low level is 0v.

1. View the downloaded schematic , It should be noted that , Pins with the same schematic name are physically connected , You can search the name of silk screen in principle to find the corresponding schematic diagram of hardware .

LED Schematic diagram corresponding to hardware

STM32 Schematic diagram corresponding to the chip

see LED Schematic diagram should achieve two purposes ( Connect or not VDD3v3 Situation judgment ）

（1） Make clear the working mode of the operating hardware （ Combined with the instruction manual of hardware ）

The corresponding pin is low ——LED bright

The corresponding pin is high ——LED destroy

（2） The hardware to operate is connected to CPU Those pins

D1——————PF9

D2——————PF10

D3——————PE13

D4——————PE14

see CPU The chip manual （STM32F4xx Chinese reference manual and Cortex-M4 Authoritative guide ） Hardware control is achieved by operating registers . There are three register configuration methods ,GPIO Register bit operation , Library function operation , Bit segment operation , The following will be introduced separately .

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GPIO Register bit operation

（1）GPIO I / O selection

Input ———— Floating space , On / Drop down input , Reuse , simulation

Output ———— push-pull / Open a leak , On / The drop-down , Reuse , simulation

The difference between push-pull and open drain ： Push pull is to pull up , Opening a leak is a weak pull up , Opening the drain and raising the resistance requires external pull-up , Leakage opening also has the function of absorbing current , Can do two-way IO

（2） Output speed

low —— in —— high —— fast

（3） Locking mechanism

lock GPIO Configuration of

（4） Data register

Input data register ———— obtain GPIO Input level

Output data register Set up / Reset register ———— Set up GPIO Output level

（5） Function reuse options

Select multiplexing register

（6） Configuration register

Look up the table to determine the value of register configuration

Check the corresponding hardware register

Stm32f407 share 9 Group GPIO（A~I）, Each group 16 individual （0~15）,stm32 All registers are 32 Bit .

Check the information you need to get from the hardware register

1. Get the address of the hardware register

stm32 The address of the register in uses the base address + The offset       

The base address is in the reference manual 2.3 Query in the table of section

such as GPIOF The base address of the register =0x40021400, If there is an offset, add the offset

The offset of each register is on the description of the register    

2. The contents represented by each bit of the register

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Do a simple exercise

To configure PF9 The register is General push-pull output , No up and down , High speed output

Mode register

Base address = 0x40021400

（7） Configuration mode register

Bit operation configuration , More trouble

Volatile unsigned int *pxx = (unsigned int*)0x40021400;

// take 18~19 Bit is set to 01

*pxx &=~(0x3<<18);  // Bits and operations , First the 18~19 Bit is set to 00

*pxx |=~(0x1<<18);  // Bitwise OR operation , then 18~19 Bit is set to 01

Configure the output type register

Configure the output speed register

Pull up and down to select register

Through the above 4 The configuration of registers is completed PF9 The initialization , General push-pull output , No up and down , Fast output , The following is through reset / The set register controls the level of the output .

Here through configuration GPIO Set up / Reset register To control GPIO Output register Output level of , To configure PF9 register , The working principle we need to understand is （ Please look carefully at the register configuration matching relationship in the above figure , This is very important ）：

The first point ： Set the reset register BS9 Write in bit 1, Output register ODR9 The position will be set 1, Set the reset register BS9 Write in bit 0, Output register ODR9 The position will not change ;

Second point ： Set the reset register BR9 Write in bit 1, Output register ODR9 The position will be cleared 0, Set the reset register BR9 Write in bit 0, Output register ODR9 The position will not change ; This is through GPIO Set up / Reset register control GPIO Method of outputting the output level of the register .

to want to GPIO Normal work , Must be turned on GPIO Clock switch , Configure through the peripheral clock enable register

Base address ：0x40023800

Write drivers

Stm32 The macro definition of register address is officially provided , You can use it directly .

The idea of writing code （ Pseudo code ）

1. initialization

   Start GPIO The clock

   take PF9 Configured as universal push-pull output , No up and down , High speed output

1. flashing

   While（1）{

         bright

         Time delay

         destroy

         Time delay

}

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GPIO The use of library functions , You can find it through the source code or library function manual

（1）GPIO Library function initialization

Void GPIO_Init(GPIO_TypeDef*GPIOx ,GPIO_TypeDef*GPIO_InitStruct);

  GPIOx ———— Which group GPIO

  GPIO_InitStruct ————GPIO Initialize structure

Typedef struct

{   

Uint32_t GPIO_Pin;                // Which pins of this group are initialized

GPIOMode_TypeDef  GPIO_Mode;   // Mode selection

GPIOSpeed_TypeDef  GPIOSpeed;   // Output speed

GPIOOType_TypeDef  GPIOOType;  // The output mode

GPIOPuPd_TypeDef   GPIO_PuPd;  // Select... From the drop-down list

}GPIO_InitTypeDef;

（2）AHB1 Bus clock enable

Void RCC_AHB1PeriphClockCmd(uint32_t RCC_AHB1Periph,FunctinalStste NewState);

RCC_AHB1Periph———— Which clock    RCC_AHB1Periph_GPIOF

NewState———— Can make / close         ENABLE/DISABLE

（3） Set up GPIO Output value

void GPIO_SetBits(GPIO_TypeDef*GPIOx,uint16_t GPIO_Pin);

void GPIO_ResetBits(GPIO_TypeDef*GPIOx,uint16_t GPIO_Pin);

Parameters ：

GPIOx———— Which group of pins

GPIO_Pin———— Which pins

stay keil5 Add source code , The source file should be added to the project directory on the left of the project , The path of the header file is added to the configuration interface C/C++ Of include paths in

 

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GPIO Bit segment operation

The operation of registers is usually in binary , Relatively speaking, it is not so convenient ,stm32 Bit segment operation is provided to allow developers to access some bits in the register more conveniently and efficiently . Bit segment operation is convenient for programming , It also improves the running efficiency of the code , If register access is frequent , You can use bit segment operations .

bit_word_adddr = bit_band_base+(byte_offset*32）+(bit_number*4)

bit_word_adddr  Represents the address of the word to be mapped to the target bit in the alias area

bit_band_base  Represents the starting address of the alias area

byte_offset     Represents the byte number in the bit segment area where the target bit is located

bit_number     Bit position representing the target bit （0-7）

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practice

utilize GPIO Library function configuration PF9,PF10 Pin is output mode , Push pull output , High speed output , No up and down

// Function code 

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);
}