Arduino uno R3 register writing method (1) -- pin level state change

Have studied 51 or STM32 Of , In particular STM32 The developers of register have a deep understanding and pain , because arduino The encapsulated function of , Make us in use , Don't look for the corresponding register , We only need to use the corresponding function , Once configured, it can be used . This is really the gospel of Xiaobai .arduino UNO It uses ATMEGA328P yes AVR A model of SCM , frequently-used Ardunio UNO and Arduino Pro Mini Are based on this chip , I studied arduino Register writing of , Make a note of . After saving, I forgot .

Statement ： The author has never been in contact with AVR The writing method of single chip microcomputer , All the research materials come from Du Niang . Grammatical error or usage error , Welcome learned people to point out the maze

There are pairs in the official arduino Detailed annotation of relevant registers and pins of

![ Insert picture description here ](https://img-blog.csdnimg.cn/369a3b2b7eb84d9fb2846a3bec8549cf.png
You can see from the picture ,
D0–D7 yes PD register
D8–D13 yes PB register
A0–A5+RESET yes PC register

Now we know the location of the register , How to use it ？ Suppose we need to change the pin state
We need to understand three instructions first

DDRx --------- Control the output direction ; // Set the input / output mode of the register pin （0： Input ;1： Output ）
PORTx - Control output data 0、1; // Change the level state of the register pin
PINx — control ( Read ) input data ; // Read the level state of the register pin

Bold in instructions x Represents the register to be used ,
For example, to use D0—D7 Of , We used PD register , So that is

DDRD
PORTD
PIND

The basic introduction has been finished , Direct program comparison , Let's feel , If you want to light up D2 This pin

Let's first look at the usual writing

Look at the register writing

//#include <avr/io.h> // If the compilation is wrong , Then this function is introduced 
void setup() {
    
 DDRD=0B00000100;  //  The binary order is D7--D0;1 For export ,0 For input  
 PORTD=0B00000100; //  The binary order is D7--D0;1 High level ,0 Low level  
}
void loop() {
      

}

The simulation results are as follows

Compare from one pin , We can see , Use register usage , You can use very small program storage space . Of course , This is a direct comparison , It makes no sense , Like playing hooligans . Functions are the encapsulation of registers , There are many things to call , It's like a middleman . It's easy to use, but of course it has to pay a certain cost .
Now let's take a look at the read pin status , This time we use A0-A5 To see the data

//#include <avr/io.h> // If the compilation is wrong , Then this function is introduced 
void setup() {
    
 
 DDRC=0B000100;    //  The binary order is A5--A0;1 For export ,0 For input  
 PORTC=0B000100;   //  The binary order is A5--A0;1 High level ,0 Low level  
 Serial.begin(9600);
 Serial.print(PINC,BIN); //  Read PC The pin status of the register 
}
void loop() {
      

}

Simulation results

I will continue to introduce later , Update from time to time