当前位置:网站首页>What is the use of entering the critical point? How to realize STM32 single chip microcomputer?
What is the use of entering the critical point? How to realize STM32 single chip microcomputer?
2022-07-06 08:01:00 【Infinite MCU programming】
Hello everyone , I am boundless .
Once I was broadcasting live to internal students , A few friends asked me , Why enter the critical , What's the use of criticality ?
At that time, I didn't expect a good explanation , Today, let me give you a few examples to answer .
If any boss thinks I'm wrong, please talk privately and I'll correct it , Don't secretly spray me in the comment area , Can't I change it yet .
Enter critical and exit critical , My first contact was in ucos System , At that time, I also felt that this professional term was awesome and complicated .
When I finish talking , You'll find it's actually quite low.
Entering the critical point is to shut down the MCU and interrupt , Exit critical It is to resume the interruption of single chip microcomputer , Remember, it's best to recover , Not open , Because before entering the critical point, the total interruption of MCU may not be on .
Then why enter the critical ? What's the role ?
Let's suppose a scenario :
Let's look at this piece of code .
Suppose our program runs to 12 That's ok , That is to say a = 0 The location of ,*p The value of must be equal to 2 Right? ?
Suddenly a timer interrupts , Then in the timer interrupt handler , We did p++.
After execution, return to the main program to continue execution , That is to say, I will implement 13 Line code , This is the time *p Guess the value of ?
you 're right , Definitely not 2, It is 3.
Obviously, the condition judgment is 2, Finally, the value becomes 3, such bug It's estimated that it can make you cry .
At this time, entering the critical point is very stable , It can be changed to the following code .
STM32 Unlike 51 SCM is so direct EA=0 You can turn off the total interrupt , But through __get_PRIMASK and __set_PRIMASK To do it , You can also use it __disable_irq and __enable_irq.
Specifically, you can search in the project , Read notes .
Every single chip microcomputer turns off the total interrupt in a different way , So there is also a difference between entering the critical code and exiting the critical code .
You just need to remember The essence is to shut down and interrupt , After executing the procedure , Just restore the total interruption .
Don't worry too much about how to switch when the single chip microcomputer is always interrupted , You can find it on the Internet .
Then continue to talk about our above program , A lot of people would say , I avoid this problem when writing programs , Not in the timer right p Just operate the pointer ?
If you are doing some big projects , Almost impossible to avoid , For example, our queue algorithm .
We will receive the data in the serial port interrupt , Put the data in the queue , Then analyze in the main function .
After using the queue , The stability of data transmission can be greatly improved , Even if the data transmission is fast , There is a large amount of data, and there will be no packet loss .
Let's take a look at the listing function of the queue algorithm .
such , If you don't use a pointer , It is almost impossible to achieve , Even the flexibility and portability are not high .
Just imagine , If this kind of pointer is frequently operated in the main function and interrupt , Without criticality, the program is easy to crash due to abnormal pointer pointing or program logic problems caused by data disorder .
Of course , In addition to protecting global variables 、 Array 、 Structure and other data are not bad, except , It can also be hardware data , such as IO、SCI、SPI、flash.
Of course ,RTOS Maybe it's more complicated , I won't explain it here , Just understand the essence .
边栏推荐
- Solution: intelligent site intelligent inspection scheme video monitoring system
- 1204 character deletion operation (2)
- Generator Foundation
- The ECU of 21 Audi q5l 45tfsi brushes is upgraded to master special adjustment, and the horsepower is safely and stably increased to 305 horsepower
- C语言自定义类型:结构体
- Analysis of Top1 accuracy and top5 accuracy examples
- CAD ARX gets the current viewport settings
- Wireshark grabs packets to understand its word TCP segment
- The Vice Minister of the Ministry of industry and information technology of "APEC industry +" of the national economic and information technology center led a team to Sichuan to investigate the operat
- IP lab, the first weekly recheck
猜你喜欢
Asia Pacific Financial Media | "APEC industry +" Western Silicon Valley invests 2trillion yuan in Chengdu Chongqing economic circle to catch up with Shanghai | stable strategy industry fund observatio
[nonlinear control theory]9_ A series of lectures on nonlinear control theory
NFT smart contract release, blind box, public offering technology practice -- contract
wincc7.5下载安装教程(Win10系统)
链表面试题(图文详解)
[untitled]
"Designer universe" Guangdong responds to the opinions of the national development and Reform Commission. Primary school students incarnate as small community designers | national economic and Informa
Easy to use tcp-udp_ Debug tool download and use
[redis] Introduction to NoSQL database and redis
National economic information center "APEC industry +": economic data released at the night of the Spring Festival | observation of stable strategy industry fund
随机推荐
远程存储访问授权
Asia Pacific Financial Media | designer universe | Guangdong responds to the opinions of the national development and Reform Commission. Primary school students incarnate as small community designers
22. Empty the table
TiDB备份与恢复简介
使用 TiUP 升级 TiDB
Solution: intelligent site intelligent inspection scheme video monitoring system
Golang DNS write casually
861. Score after flipping the matrix
解决方案:智慧工地智能巡檢方案視頻監控系統
(lightoj - 1410) consistent verbs (thinking)
Description of octomap averagenodecolor function
Artcube information of "designer universe": Guangzhou implements the community designer system to achieve "great improvement" of urban quality | national economic and Information Center
Data governance: misunderstanding sorting
备份与恢复 CR 介绍
Convolution, pooling, activation function, initialization, normalization, regularization, learning rate - Summary of deep learning foundation
IP lab, the first weekly recheck
DataX self check error /datax/plugin/reader/_ drdsreader/plugin. Json] does not exist
Vit (vision transformer) principle and code elaboration
指针和数组笔试题解析
数据治理:数据质量篇