STM32 introductory tutorial lesson 2

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STM32 Introductory tutorial lesson 2 ------ Introduce GPIO

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Catalog

List of articles

Preface

One 、GPIO What is it? ？

1. Brief introduction GPIO

2.GPIO The basic structure

Two .GPIO Introduction to the mode of ( Four inputs and four outputs )

1. Floating input _IN_FLOATING:

​ edit

2. Analog input _AIN ​ edit

3 With pull-up input _IPU 

4 . With drop-down input _IPD

5. Open drain output _OUT_OD

6. Push pull output _OUT_PP

7. Open drain multiplexed output _AF_OD

8.  Push pull multiplex output _AF_PP

  3、 ... and 、GPIO How to use

           1. First step , Use RCC Turn on GPIO The clock ：

        2. The second step , Use GPIO_Init Function initialization GPIO：

         3. The third step , Use output and input functions to control GPIO mouth , With a little LED For example ：

  

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Preface

In the previous article, we learned how to build a stm32 Of keil engineering , Let's talk about it in detail GPIO

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One 、GPIO What is it? ？

1. Brief introduction GPIO

  Let's first introduce GPIO,GPIO(General Input Output) It is a general input and output port , It can be configured into eight input and output modes , Pin level ：0—3.3V, Some pins tolerate 5V.

The output mode —— It can control the output high and low levels of the port , To drive LED, Control the buzzer , Analog communication protocol output timing, etc ;

The input mode —— It can read the high and low level or voltage of the port , Used to read key input , External module level signal input ,AOC Voltage acquisition , Analog communication protocol, receiving data, etc .

2.GPIO The basic structure

Two .GPIO Introduction to the mode of ( Four inputs and four outputs )

1. Floating input _IN_FLOATING:

 

When GPIO When using floating input mode ,STM32 The pin state of is uncertain ,I/O The level signal of the port directly enters the input data register . here STM32 The resulting level state depends entirely on GPIO External level status , So in the GPIO The external pin is suspended （ Without signal input ） when , Reading the level state of the port is an uncertain value . 

Usually used for IIC、USART.

2. Analog input _AIN 

It's easy to understand , The most common occasion is ADC Analog input , Unlike other input modes, only 0 and 1, Analog input mode can read very small changes in values ,I/O Analog signal of the port （ Voltage signal , Not the level signal ） Direct analog input to on-chip peripheral modules , such as ADC Module etc. . Analog signals are generally ：3.3v 5v 9v. 

3 With pull-up input _IPU 

 

External interrupt mode with rising edge trigger detection  , Compared with the floating input mode described earlier , Just on the data channel , A pull-up resistor is connected , according to STM32 The data book for , The pull-up resistance is between 30K~50K ohm . Again ,CPU At any time “ Input data register ” On the other end of , Read through the internal data bus I/O The state of the level change of the port .

4 . With drop-down input _IPD

 

  Pull down input mode ,I/O The level signal of the port directly enters the input data register . But in I/O The port is suspended （ No signal input ） Under the circumstances , The level of the input terminal remains low ; And in I/O When the port input is high , The input level is also high .

5. Open drain output _OUT_OD

 

Open drain output mode （ Pull up resistance +N-MOS tube ）, Set... By setting bit / Clear the value of the register or output data register , Via N-MOS tube , Finally output to I/O port .

Can output 0 and 1, It is suitable for occasions with mismatched levels , To get a high level, you need to pull up the resistor .

6. Push pull output _OUT_PP

  In push-pull output mode （P-MOS tube +N-MOS tube ）, Set... By setting bit / Clear the value of the register or output data register , Via P-MOS Tube and N-MOS tube , Finally output to I/O port .

Can output high and low level 0 and 1, Applicable to two-way IO Use .

7. Open drain multiplexed output _AF_OD

Open drain multiplexing output mode , It is very similar to the open drain output mode . Just the source of the high and low levels of the output , Not let CPU Write directly to the output data register , Instead, it is determined by using the multiplexing function output of the on-chip peripheral module . 

8.  Push pull multiplex output _AF_PP

Push pull multiplexing output mode , It is very similar to the push-pull output mode . Just the source of the high and low levels of the output , Not let CPU Write directly to the output data register , Instead, it is determined by using the multiplexing function output of the on-chip peripheral module . 

In one sentence, distinguish between open drain and push-pull output ：

Both high and low levels of push-pull output have driving ability
Open drain output high level has no driving ability , Low level has driving ability

  3、 ... and 、GPIO How to use

        1. First step , Use RCC Turn on GPIO The clock ：

        Code up ：

	RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOC,ENABLE); Start RCC The clock 

         The detailed steps ： stay libraries in --stm32f10x_rcc.h in ：

Find the definition of the following library function ： 

It's about GPIO Clock open library function definition , Which one to choose depends on your project needs  

With APB2 For example , Go to function definition ：

Go straight to the code ：

/**
  * @brief  Enables or disables the High Speed APB (APB2) peripheral clock.
  * @param  RCC_APB2Periph: specifies the APB2 peripheral to gates its clock.
  *   This parameter can be any combination of the following values:
  *     @arg 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     
  * @param  NewState: new state of the specified peripheral clock.
  *   This parameter can be: ENABLE or DISABLE.
  * @retval None
  */
void RCC_APB2PeriphClockCmd(uint32_t RCC_APB2Periph, FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_RCC_APB2_PERIPH(RCC_APB2Periph));
  assert_param(IS_FUNCTIONAL_STATE(NewState));
  if (NewState != DISABLE)
  {
    RCC->APB2ENR |= RCC_APB2Periph;
  }
  else
  {
    RCC->APB2ENR &= ~RCC_APB2Periph;
  }
}

According to the I/O Determine the first function parameter , then ENABLE Is the second parameter ;

The clock starts successfully .

2. The second step , Use GPIO_Init Function initialization GPIO：

Code up ：

GPIO_Init(GPIOA,&GPIO_InitStructure);

The detailed steps ： go to GPIO_Init Function definition ：

/**
  * @brief  Initializes the GPIOx peripheral according to the specified
  *         parameters in the GPIO_InitStruct.
  * @param  GPIOx: where x can be (A..G) to select the GPIO peripheral.
  * @param  GPIO_InitStruct: pointer to a GPIO_InitTypeDef structure that
  *         contains the configuration information for the specified GPIO peripheral.
  * @retval None
  */
void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)
{
  uint32_t currentmode = 0x00, currentpin = 0x00, pinpos = 0x00, pos = 0x00;
  uint32_t tmpreg = 0x00, pinmask = 0x00;
  /* Check the parameters */
  assert_param(IS_GPIO_ALL_PERIPH(GPIOx));
  assert_param(IS_GPIO_MODE(GPIO_InitStruct->GPIO_Mode));
  assert_param(IS_GPIO_PIN(GPIO_InitStruct->GPIO_Pin));  

According to the I/O Determine the first function parameter , With GPIOA For example , So the first parameter is GPIOA, According to the function definition , The second parameter needs to define the structure ;

Code up ：

GPIO_InitTypeDef GPIO_InitStructure;
 Defining structure , If you make a mistake 268, You can put this line in RCC Above the clock , Put it in RCC The following words need to be in the compiler magic wand -C/C++ Change it to C99
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_Out_PP;// Push pull output 
GPIO_InitStructure.GPIO_Pin=GPIO_Pin_13;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;

After the first line declares the structure , Three contents of the structure are introduced below , The following describes the method in detail :

 First, first GPIO_Mode

GPIO_InitStructure.GPIO_Mode=GPIO_Mode_Out_PP;// Push pull output 

go to GPIO_Mode Definition ： 

 GPIOMode_TypeDef GPIO_Mode;  
  /*!< Specifies the operating mode for the selected pins.
           This parameter can be a value of @ref GPIOMode_TypeDef*/

Continue to   GPIOMode_TypeDef：

It's an enumeration ：

/** 
  * @brief  Configuration Mode enumeration  
  */

typedef enum
{ GPIO_Mode_AIN = 0x0,
  GPIO_Mode_IN_FLOATING = 0x04,
  GPIO_Mode_IPD = 0x28,
  GPIO_Mode_IPU = 0x48,
  GPIO_Mode_Out_OD = 0x14,
  GPIO_Mode_Out_PP = 0x10,
  GPIO_Mode_AF_OD = 0x1C,
  GPIO_Mode_AF_PP = 0x18
}GPIOMode_TypeDef;

Select according to the needs of the project , Take push-pull output as an example ： choice   GPIO_Mode_Out_PP, therefore ,Mode Get it done .

GPIO_InitStructure.GPIO_Mode=GPIO_Mode_Out_PP;// Push pull output 

In the same way ：GPIO_Pin and GPIO_Speed;

It should be noted that , turn GPIO_Pin Select member, Here's the picture ：

  After all is written , Structure definition completed
 

	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Push pull output 
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 ;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz ;

thus ,GPIO_Init Write well ：

	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Push pull output 
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 ;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz ;
	GPIO_Init(GPIOA,&GPIO_InitStructure);
	// Up to the top ,GPIO Initialization complete 

 3. The third step , Use output and input functions to control GPIO mouth , With a little LED For example ：

On the first code ：

	GPIO_SetBits(GPIOC,GPIO_Pin_13);// take PC13 Set the port to high level 		（ The light goes out ）
	GPIO_ResetBits(GPIOC,GPIO_Pin_13);// take PC13 Set the port to low level  （ Light on ）

Go to function definition and write parameters according to project requirements , I won't explain it in detail , The next issue will explain control in detail LED The operation of

thus ,GPIO Introduction complete .

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