Implementation of command batch processing in serial communication between PC and microcontroller

    Abstract: This article introduces the implementation ideas, methods, communication protocols and C51 program platform of batch processing commands for communication between PC and MCS-51 microcontroller. It provides a new method for the design of serial communication program between PC and microcontroller.

    Keywords: Batch processing MCS-51 microcontroller communication protocol

The serial communication between the PC and the MCS-51 microcontroller is basically one-to-one, that is, every time the PC sends a command to the microcontroller, it waits for a return message from the microcontroller. This may waste a lot of time in the communication process between the PC and the microcontroller. For this reason, after practice, the author has designed a system that can execute commands sent by the PC to the microcontroller in batches. Just like the batch commands in the DOS operating system, the information can be processed in batches continuously. As a result, the system speed is certainly improved. This article provides part of the platform C51 software source code for your reference.

1 Communication protocol

(1) Communication data format

PC→MCS-51 microcontroller data format is listed in Table 1.

Table 1

MCS-51 microcontroller→PC data format is listed in Table 2.

Table 2 

(2) Initial communication parameters

　　Between PC and microcontroller (9600, n, 8, 1)That is, the baud rate is 9600 baud, 1 start bit, 8 data bits, 1 stop bit, and no parity.

(3) Data sending and receiving method

　　All data is sent as binary single bytes.

(4) Sending data sequence

　　Send synchronization code (1Byte): Stx=0X60

　　Send the length of subsequent bytes (2Byte): Len=2+N

　　Send Len subsequent data bytes (N+2 Byte): CommandH, CommandL, Data[0]…Data[N-1]

　　Send verification code (1Byte): Edc=Stx^CommandH^ CommandL^Data[0]^…Data[N-1]

　　Send end code (1Byte): Etx=0X03

2 Single command COMMAND[n]

COMMAND[n] format:

Generally, the length of a single command is controlled within 255.

The data sequence sent by the PC to the microcontroller is:

STX, LENH, LENL, COMMANDH, COMMANDL, DATA...DATA, EDC, ETX

3 Thinking methods of batch processing

(1) Batch command BATCH_COMMAND (0X0000)

PC format:

NUM - the number of subsequent commands;

Flag - the flag that needs to be returned (00 means data is to be returned,Others do not need to return data).

COMMAND[i]=LEN, subcommand body

Function: Batch execution function.

Return status and data: Determine whether to return data according to the Flag flag, and return data in the order of sending commands.

(2) Commands to control batch transfer

Function: No data or status is returned, and the lower computer is controlled to jump.

① Control BATCH_If (0X0001) for judgment and conditional execution of commands

Function: When the microcontroller encounters this command, it performs judgment. If the result is logically true, it executes the first command following BATCH_If; otherwise, it executes the second command following BATCH_If.

PC format:

num: Returns the number of data from right to left. When it is 0, it is the low-order byte of the status data;

EQUAL/NOT - 00 means equal, 1 means unequal;

VALUE – Numeric value.

Returns: None.

② Control BATCH_Break (0x0002) to jump out of the loop command

Function: Used to jump out of the BATCH_While loop.

PC format:

Returns: None.

③ Control BATCH_While (0x0003) to loop and execute the commands in the loop body

Function: cyclically execute the commands in the loop body.

PC format:

Returns: None.

④ Control BATCH_Return (0x0004) to exit the packaging program block

Function: Exit the packaging program block.

PC format:

Returns: None.

(3) Precautions

◇ BATCH _While loop cannot be used nested;

◇ BATCH _Break can only be used within the body of the BATCH _While loop;

◇ Commands that need to obtain returned data immediately should generally not be placed in batch processing.

(4) Examples of PC commands that control the transfer of packaging programs

The code transferred from the PC to the microcontroller: BATCH_ COMMAND

    Reader_Version(): assumed to be 0X1001

The actual code downloaded from the PC is (HEX format):

60 28 00 00 06 01 00 03 00 00 05 01 00 04 00 01 00 00 03 01 00

02 00 02 01 00 05 00 01 05 00 61 01 00 02 00 04 00 00 02 10 01 Check code 03

4 Program flow

Each program flow is shown in Figure 1 to Figure 4.

5 parts of source code

Due to space limitations, only part of the source program is provided here.

(1) Main program

The main program first receives the data, analyzes the data, and distinguishes between batch processing and single commands; then executes the command; and finally returns the results and uploads them to the PC. The program list can be found in the supplementary version of this journal's website (website address: http://www.dpj .com.cn).

(2) Batch processing program

The batch processing program distinguishes the control transfer commands with flags, executes the commands by interpreting the command sequence, and finally packages the results according to the communication data format and uploads them to the PC. The program list can be found in the supplementary version of this journal's website.

Conclusion

This article explores the software programming of serial communication between PC and microcontroller to realize the processing of batch information data communication. I believe that this new idea and method will develop and be applied to actual embedded systems soon.