Report on the double computer experiment of scoring system based on 485 bus

Originally, I was thinking about making long machines , But the teacher has already graded it . To compress to 6 A lot of content has been deleted from the page , Make do with it

be based on 485 Experimental report of scoring system of bus

The goal of the experiment ：

Deepen the understanding through this case RS485 communication mode , The main controller of the upper computer communicates with all the lower computers .

B Level task

The experimental requirements ：

Use two STC Download the provided in the previous section .hex file , build 485 Dual computer communication circuit , stay linux Program code for scoring in .

Experimental resources ：Windows10 The computer ,Ubuntu18.04, Single chip microcomputer , DuPont line

The experimental steps ：

1. Read the flow chart of the program system , Clarify the functional requirements of dual computer communication .

2. Be familiar with the simulation in the previous section MODBUS Packet structure of the protocol , Relevant function codes and additional data definitions

3. review 485 Bus data transceiver experiment , Build a dual computer communication circuit .

4. PC The end serial port settings are as follows ： Serial port baud rate ：9600 Data bits ：8 position Check bit ： nothing Stop bit ：

5. Written PC The end program should complete a complete scoring process by referring to the communication protocol in the previous section ：

• You need to include the settings of the serial port

• The master node initiates the slave detection process ： Send the normal detection packet of the specified slave number , Judge whether the response query packet conforms to the communication protocol in the previous section .

• The master obtains the scoring process of the slave ： Send the data package related to the specified slave scoring , Judge whether the response query packet conforms to the communication protocol in the previous section .

• The host initiates the process of ending the scoring , If reset succeeds ,STC From the plane 1 Position and number 8 position LED The light will go out .

• Display serial port related information , Display the detected slave number and the score of the slave .

Code design ideas ：

1. Define several functions to be used in this experiment ：

string format(const vector<uchar> &data);		  // Data is processed into strings 
int check(serial &pipe, int addr);				 // Equipment inspection 
int get_score(serial &pipe, int addr);			  // Get points 
void reset(serial &pipe);				         // Slave reset 

2. Next is the main function , First, read the data from the MCU , The baud rate is set to 9600（ The title has been given ）

serial pipe("/dev/ttyUSB0", B9600);

3. Then select the desired function according to the requirements of the topic and user input . The first is to find the corresponding score according to the number of MCU , The second is to reset the slave , The third is to exit the program , Repeat the user's selection by setting a cycle . The specific code is as follows ：

    while(1){
    
        cout<<"-------------------- be based on RS485 Bus scoring system -------------------------"<<endl;
        cout<<" Enter description ：\n1.  Enter the legal slave address to query the score \n2.  Input -2 Reset the slave \n3.  Input -1 Exit procedure \n Please enter the command ：";
        cin>>addr;
        if(addr == -1) break;
        if(addr == -2) {
    
            reset(pipe);
            continue;
        }
        check_ret = check(pipe, addr);
        if(check_ret == 1){
    
            cout<<" Equipment detection is normal "<<endl;
            sleep(1);
    	    if(!(score = get_score(pipe, addr)))
    	        cout<<" Failed to get score "<<endl;
    	    else 
    	        cout<<" fraction ："<<score<<endl;
        }
        else if(check_ret == 0){
    
            cout<<" Wrong address , Please enter the address and try again "<<endl;
            continue;
        }
	else{
    
	    cout<<" Data transmission error , Please restart the slave "<<endl;
	}        

        //reset(pipe);
        cout<<" The slave has been reset , Input -1 sign out "<<endl;
    }

You can see , Input -1 To exit the loop , then return 0 Exit procedure . Input -2 Called when the reset Function to reset the slave . After inputting the correct slave number, the corresponding result will be output , Mainly by calling check Function to check whether the slave number is correct , call get_score To get grades , Next, we will analyze the implementation ideas of these three functions .

4.reset Function complete code ：

void reset(serial &pipe){
    
	vector<uchar> code = {
    0x5a, 0x00, 0x01,0x00,0x5b};
	//cout <<"reset:"<< format(code) << endl; 
	/*  Send packet  */
	for(int i=0;i<600;i++) {
    
	    pipe.myWrite(code);
	}
	return;	    
}

The parameter value is serial Serial data , According to the experimental guidance, we can know , When the master wants to send a reset signal to the slave , Its serial number should be 5a + Broadcast address 00 + Reset function code 01 + 00 + Check byte , So the implementation idea is to define a string serial number , Then the host sends data packets to the slave constantly , Finally, the slave is reset .

5.check Function complete code ：

int check(serial &pipe,int addr){
    
	int check_code = 117 + addr, ret;				// The check code is cumulative sum 
	vector<uchar> code = {
    0x5a, 0x08, 0x13};
	vector<uchar> rec;
	code.insert(code.begin()+1, (uchar)addr);			// Insert slave address 
	code.push_back((uchar)check_code);				// Insert the check code 
	//cout << format(code) << endl; 
	/*  Write and receive response packets  */
	pipe.myWrite(code);
	sleep(1);
	rec = pipe.myRead(5);
	if(format(rec) == format(code))				// Check whether the received packet is the same as the sent one , If it is the same, the slave address is correct 
	    ret = 1;
	else{
    
	    if(rec[3] == 0x6f) ret = 0;
	    else ret = -1;
	}
	return ret;	    
}

The parameters of the function are serial port data and slave address . The serial number sent by the host for data detection is 5a + Slave address + Detect function code 08 + 13 + Check code . The implementation idea is to write the data detection serial number , Then judge whether the slave address is correct according to the received data packet . If you return 1 The address is correct , return 0 The address is wrong , return -1 Explain data error .

6.get_score Function complete code ：

int get_score(serial &pipe, int addr){
    
	int check_code = 93 + addr, ret;				// The check code is cumulative sum 
	vector<uchar> code = {
    0x5a, 0x00, 0x03};
	vector<uchar> rec;
	code.insert(code.begin()+3, (uchar)addr);			// Insert slave address 
	code.push_back((uchar)check_code);				// Insert the check code 
	//cout << format(data) << endl; 
	/*  Write and receive response packets  */
	pipe.myWrite(code);
	sleep(1);
	rec = pipe.myRead(5);
	if(rec[3] == 0x6f) ret = -1;					// Check for errors 
	else {
    
	    ret = (int)rec[3];						// Turn to numbers 
	    if(ret < 0 || ret > 100) ret =-2;				// Check whether the number is legal 
	}
	return ret;	    
}

The parameters of the function are serial port data and slave address . The host sends for score acquisition, and the serial number is 5a + 00 + Read function code 03 + Slave address + Check code . The implementation idea is the same as that of the previous function , Write the data detection serial number to , Then score according to the received packets , At the same time, we should judge the legitimacy of the score . If it is correct, the correct score is returned , return -1 It indicates that the slave is not ready , return -2 Description slave error .

7.format The complete code of the function is as follows ：

string format(const vector<uchar> &data) {
    
    std::string str(2 * data.size() + 1, '\x00');
    for (int i = 0; i < data.size(); i++) {
    
        sprintf(&str[i * 2], "%02X", data[i]);
    }
    return str;
}

The main function of the function is to process data into strings , stay check Use in a function

Verification and result analysis ：

Here, the number of the lower computer is set to 2 Number , The score is 66 branch

open programs , Enter the slave number after operation 2 Attainable achievements , Input -2 Resettable slave , Input -1 Exit program

You can see , Results the correct , When inputting the correct slave address 2 when , The score is output 66. When you enter -2 when , The slave will reset , The effect is shown in the first figure , The first and eighth lights on the MCU go out . When the input -1 when , Exit the program directly .

Summary of the experiment ：

• The humanities ： Recognize the importance of communication . Many problems that I don't understand have been effectively solved by communicating with my classmates . At the same time, you can ask the teacher modestly when you encounter problems .
• knowledge ： Master the knowledge based on 485 The working principle and specific implementation of the scoring system of bus . Learned how to obtain serial port data , And use serial port data to make some judgments . Also learned how to use c++ To realize based on 485 Dual computer scoring of bus scoring system .
• Skill ： Can quickly write c++ Code , At the same time, the use of SCM and serial assistant software is more handy , Some keys of single chip microcomputer can be used simply .