[STM32] (I) overview and GPIO introduction

Preface

   For a variety of reasons ,STM32 It is imperative to study , Can't , But for high-quality learning , I first collated and summarized many materials I found before , I plan to write a systematic study note .

For a single-chip learning , I think we should generally pay attention to the following points ：

• Specify chip pins and on-chip peripherals , Such as IO mouth , interrupt , Timer , Serial port ,ADC etc.
• Data manual , It is convenient to refer to the register or program responding to the query when using a module
• routine , Generally speaking , The official will give a certain routine , It is convenient for users to learn and use .
• Practice more

Reference link

• Automation Association of Jiangke University _STM32 Introductory tutorial _bilibili—— It's really very detailed , Recommendation of conscience ！

The following text and pictures are mostly from the content in this video tutorial .

STM32F103 summary

  STM32 yes ST（ Italian French semiconductor ） The company is based on ARM Cortex-M Kernel developed 32 Bit MCU , So-called M, namely Microcontroller An acronym for ,32 Represents that the single chip microcomputer is 32 position .

Core understanding and product selection

  STM32 Is based on ARM Kernel design , But it seems that many people can't distinguish the relationship between kernel and MCU . This video details this point . As shown in the figure below ：

   Simply speaking , Namely ARM The company provides cores , then ST The company improves the peripheral memory and peripherals , Make the single chip microcomputer have different functions . Besides , Other SCM companies will also be based on ARM Kernel to add other types of peripherals （Peripherals）, Thus forming be based on ARM Kernel but function 、 SCM products of different models .
   About ARM The various models of the kernel are shown in the figure below ：

   among ,Cortex-M Series is mainly used for embedded and single chip computers , That's what we're used to STM32F103 The kernel of . Other product cores and features are shown in the figure below ：

System structure diagram

   You can see from the manual , Small 、 in 、 The internal structure of high-capacity products is similar , As shown in the figure below ：

   among ,Cortex-M3 For the kernel ,ICode and DCode Instruction bus and data bus related to the kernel , Used to perform Flash Program instructions in ,System For system bus , Used to connect other peripherals .AHB（Advanced High performance Bus） For advanced high-performance bus , Used to connect peripherals with high performance requirements , Like a clock RCC And reset .APB1 and APB2（Advanced Peripheral Bus） For advanced peripheral bus , Used to connect peripherals on the chip , among APB2 The maximum clock is 72MHz,APB1 The maximum clock is 36MHz, because APB1、APB2 The clock and AHB There are some differences , Therefore, a bridge circuit is needed .
   Here's the thing to remember , Which peripherals are connected APB1, What are connections APB2, Because it is generally necessary to enable the clock of the corresponding bus before using peripherals , Otherwise, the peripheral cannot run . among ,GPIO And peripheral devices “1 Contestant No ” Mounted on APB2 On , Other peripherals “ Not 1 Contestant No ” and ADC Mount it on APB2 On , Relatively slow .

STM32F103C8T6

   The above description is STM32F1 The function and structure of the series integrity , Specific to the smallest system board used and its chip model , Also need to have some understanding .
   This video tutorial is based on STM32F103C8T6 The smallest system board of the chip , According to the model selection manual , We can know that the main frequency of this type of chip is 72MHz, The power supply is 2.0~3.6V, General choice 3.3V Power supply .
   The circuit schematic diagram of the minimum system board is shown below ：

   Besides , Attention is also needed STM32 Start configuration of , namely BOOT0 and BOOT1 Configuration of , These two pins determine where the MCU starts to execute the program , The specific settings are shown in the figure below ：

   among , In the first mode, the program starts from the main flash memory , Is the mode of normal running program , This mode is generally used ; The second mode is to start from the system memory , That's what we call it BootLoader, Generally used as serial port download .
   Besides , According to the notes at the bottom of the table , When the system is reset ,SYSCLK Of the 4 Rising edge ,BOOT The value of the pin will be locked , At this point, you can put BOOT0 The pin configuration is normal IO Mouth .

Standard library development Keil New project

  STM32 Development mode , There are three ： Register development 、 Standard library development 、HAL Library Development , among , because STM32 All of the registers are 32 position , And a large number , So few people use registers to develop , Most of them use standard libraries or HAL Library to develop . Here we mainly introduce the development method of standard library , So just use Keil that will do .
   however , There is a big trouble in the development of standard library , That is, it is troublesome to establish engineering documents , We need to arrive first. ST Download the compressed package of the standard peripheral library on the official website , Then add some files in the project .

• 1、 Create a project , Select the corresponding device
  
  
• 2、 Create several subfolders in the project folder , Convenient for project management ：Start、Library、System、User、Peripherals, The name can be any , Easy to understand . And at the same time Keil Create a project with the same name Group.
  
     It should be noted that ： establish group after , Be sure to add the corresponding folder in the project inclusion
  
     And at the same time define Add the definition of using the standard library ：USE_STDPERIPH_DRIVER
• 3、 Open a standard library file , stay Keil Add corresponding files in the project . It's complicated here , Refer to the tutorial in the video for details

actually , If you only need some functions , You can only add some official .c and .h file , But to create a “ It's not good to try ” Project engineering template , You can add all source files and header files , It's just that the compilation speed is a little slower .

• 4、 Set the debugger according to your actual situation
  

Step on the pit diary

• 1、 Report errors FCARM - Output Name not specified, please check 'Options for Target - Utilities’
  reason ： Wrong type selection when adding files
  
  Should be changed to All files. And right click to add the file , You can find the corresponding error of its attribute .
  Reference link
• 2、 Use ST-Link Download the program to the development board , It is found that the program can only be run by pressing the reset button
  solve ： Check... In the setting Reset and run outside , You also need to uncheck Enable
  
  
  Reference link

GPIO

Additional reference links

• 【51/STM32】 Explain MCU in detail GPIO Various modes of port input and output - CSDN

summary

  STM32 Of GPIO More complicated , But after understanding the principle, it is still very simple to master the basic use . Inside IO The mouth structure is shown in the figure below ：

   among , It is worth mentioning that , Schottky trigger at input , In essence, it is a Schmidt trigger （ It's a translation error ）, It has hysteresis comparison curve , It can make the read signal not affected by fluctuations . Output terminal , Bit settings / The clear register is used to set the output data register , Because the output data register can only be read and written as a whole , And if you need to change a bit , You need to set it in place / Clear register , To write a bit , And other bits do not change the effect .
   Precisely because STM32 Of GPIO The internal structure is complex , therefore GPIO A total of... Can be configured 8 Kind of I / O mode , As shown in the following table ：

  8 The code in the standard library corresponding to each mode is shown in the following figure ：



   Generally speaking , Use GPIO The steps are as follows ：

• Can make the clock （ Can make APB2 Clock on bus ）
• initialization GPIO port , Including setting pin （Pin）、 Pattern （Mode）、 Speed （Speed） Equal parameter
• Use the corresponding API Function interface for input and output

   among , When initializing the port , Generally, you need to define a GPIO The structure of the body , Then configure the parameters in the structure separately , The reference codes are as follows ：

API Function summary

   Initialization complete GPIO After the port , Next is the operation input and output , Here we need to use all kinds of API function . How to find these functions ？ It's simple , Open the added stm32f10x_gpio.h file , Slide to the bottom , You can see the commonly used API Function .

   Although the quantity is a little more , But in fact, there are not many commonly used functions . Its function is shown in the figure below ：

   If you need to view the specific definition of the function , You can right-click the function declaration , choice Go To Definition Of xxxxx, If you need to return the function declaration , Right click the defined function , choice Toggle Head.
   Attached below is a LED Flashing code ：

#include "stm32f10x.h" // Device header
#include "Delay.h"

int main(void)
{
    
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
	
	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOA, &GPIO_InitStructure);
	
	while (1)
	{
    
		GPIO_ResetBits(GPIOA, GPIO_Pin_0);
		Delay_ms(500);
		GPIO_SetBits(GPIOA, GPIO_Pin_0);
		Delay_ms(500);
		
		GPIO_WriteBit(GPIOA, GPIO_Pin_0, Bit_RESET);
		Delay_ms(500);
		GPIO_WriteBit(GPIOA, GPIO_Pin_0, Bit_SET);
		Delay_ms(500);
		
		GPIO_WriteBit(GPIOA, GPIO_Pin_0, (BitAction)0);
		Delay_ms(500);
		GPIO_WriteBit(GPIOA, GPIO_Pin_0, (BitAction)1);
		Delay_ms(500);
	}
}

CubeMX Study the tutorial

https://zhuanlan.zhihu.com/STM32CubeMX
https://www.waveshare.net/study/article-629-1.html