CN104052579A - Automatic MODBUS-RTU communication baud rate matching method - Google Patents

Abstract

The invention discloses an automatic MODBUS-RTU communication baud rate matching method. The method is achieved through the steps of firstly, setting the baud rate of a serial port as the default baud rate when a slave station is powered on, waiting for receiving a serial port message on a bus, resetting the baud rate of the serial port as the agreed next baud rate of a master station and the slave station if the messages unceasingly received five times are wrong messages till a correct serial port message is received, and achieving communication with the master station with the baud rate; secondly, changing the baud rate of the master station under the normal communication condition, detecting whether the received message on the bus is correct or not in real time through the slave station, repeatedly executing the baud rate matching process if the wrong messages are unceasingly received five times till the correct message is received, judging the data format based on a MODBUS communication protocol according to whether the message received by the slave station is correct or not, and conducting verification, wherein a CRC verification code and the length of the whole message are mainly verified. By means of the method, the baud rate of the master station and the baud rate of the slave station can be automatically matched without changing bus communication or all devices arranged on the bus.

Description

MODBUS-RTU communication baud rate Auto-matching

Technical field

The present invention relates to field of industrial automatic control, particularly MODBUS-RTU communication baud rate Auto-matching.

Background technology

MODBUS-RTU agreement is disclosed, a to be widely used serial communication protocol, formulated for its Programmable Logic Controller and industrial automation system by Modicon company at first, while being widely used in the I/O of transmission of digital and simulation between control appliance and register data, use, this protocol definition controller can be familiar with the message structure using, and no matter they through which kind of network communicate.It has described the process of a controller request access miscellaneous equipment, how to respond the request from miscellaneous equipment, and how to detect wrong and record.It has formulated the common format of message field general layout and content, in RS-485 bus, and most of master-slave communication mode that adopts, a main frame, connects many slave stations.Main frame and slave station communication mainly rely on slave station to identify for No. ID, make main website and corresponding slave station carry out exchanges data.And the prerequisite of main website and slave station communication is, main website wants consistent with the baud rate of slave station communication, existing technology mainly adopts toggle switch that the baud rate of every slave station is set or the baud rate of slave station is set by software, the baud that needs only main website is in use changed, will will every baud rate be set to equipment on communication bus by toggle switch or software, use very inconvenient, after whole system is moved, communication is unstable especially, need to change the baud rate of bus time, the use of the long serious system that affects of needed time.

RS-485 bus communication, the devices communicating baud rate being connected on same bus must be consistent, the Configuration of baud rate of establishing of existing RS-485 communication is all to develop by dial-up, software or other mode separate units arrange, the baud rate that need to change bus communication must arrange every equipment in bus, in a bus, may there be tens equipment, every equipment arrives hundreds of rice at a distance of tens meters, likely go up km, if it is unstable that whole system is communicated by letter after moving, when need to reducing communication baud rate and strengthen the stability of communication, just need to stop whole bus apparatus operation, develop by dial-up, software or the artificial separate unit of other modes arrange, after setting up, rerun the equipment in whole bus, this process need dozens of minutes was by several hours, 1, increase the cost of labor of safeguarding of whole system, 2, stopping whole bus apparatus operation dozens of minutes can have serious consequences to whole system by several hours.

Summary of the invention

The object of the invention is the shortcoming and defect in order to overcome prior art, providing a kind of does not need to change bus communication and every equipment in bus is set, and realizes the MODBUS-RTU communication baud rate Auto-matching of the Auto-matching of master-salve station baud rate.

The present invention is achieved by the following technical programs:

The implementation procedure of MODBUS-RTU communication baud rate Auto-matching is as follows:

The baud rate that serial ports is set when 1, slave station powers on is the baud rate of acquiescence, wait for the serial ports message receiving in bus, if the continuous message receiving for 5 times is error message, just to reset serial ports baud rate be the next baud rate that master-salve station is better, until while correctly receiving serial ports message, just with this baud rate and master station communication;

2, the in the situation that of proper communication, main website has changed baud rate, and whether the message the standing-meeting bus that detection receives in real time is correct, if continuous 5 times receive error message, repeats baud rate matching process, until receive correct message.Whether correctly the message that slave station the receives data format of basis for estimation MODBUS communication protocol carries out verification, main check (CRC) check code, whole message length.

The invention has the beneficial effects as follows, master-salve station has been arranged several baud rates (9600,19000,38400,57600,93750,1115200,187500,250000,300000,500000,1000000,2000000,2500000bit/s), can change as required, main website can change the communication baud rate in whole bus according to a preconcerted arrangement, when main website changes baud rate, slave station automatically mates with main website baud rate, correctly communicates by letter thereby realize principal and subordinate.

Brief description of the drawings

Fig. 1 is slave station and main website baud rate Auto-matching schematic flow sheet.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described.

Slave station as shown in Figure 1 and main website baud rate Auto-matching, following code, based on STM32F103 chip, has called the storehouse of STM32F103, specifically describes as follows:

/*

Slave station communication baud rate combination definition

*/

#define UART_RXBUF_DMA_LEN 300

const unsigned int ASC_Baudrate_Const[15]=

{

9600,19000,38400,57600,93750,1115200,187500,250000,300000,500000,1000000,2000000,

2500000

};

Unsigned char ASCRevBuf[300];

Unsigned char BaudrateInde=0;

Unsggned char ASCRevErroNum=0;

uint32_t AscDMA_Ptr=0;

/*

Serial ports reception & disposal (using serial communication dma mode)

*/

void OnASC2_Event(void)

{

uint16_t i = 0;

uint32_t TempCount,CurrentPos;

Unsigned char ASCRevErroSign=0;

if(USART_GetITStatus(USART2, USART_IT_IDLE) != RESET)

{

TempCount = USART2->SR;

TempCount=USART2->DR; // removing serial ports receive interruption mark

/*

Calculate the length that receives message

*/

CurrentPos=UART_RXBUF_DMA_LEN - DMA_GetCurrDataCounter(DMA1_Channel6);

if(CurrentPos>AscDMA_Ptr)

{

TempCount=CurrentPos-AscDMA_Ptr;

}

else

{

TempCount=CurrentPos+(UART_RXBUF_DMA_LEN-AscDMA_Ptr);

}

/*

The serial ports message COPY receiving is arrived to reception buffer zone

*/

If(TempCount<300)

{

for(i=0;i<TempCount;i++)

{

ASCRevBuf [i]=Uart1_RxBuf_DMA[AscDMA_Ptr];

AscDMA_Ptr++;

if(AscDMA_Ptr>=UART_RXBUF_DMA_LEN)

{

AscDMA_Ptr=0;

}

}

}

Else

{

ASCRevErroSign=1;

}

Whether correctly/* judges serial ports message (CRC check is according to MODBUS standard implementation) receiving

if(ModbusCRCVerify(ASCRevBuf, TempCount)!=0|| ASCRevErroSign)

{

ASCRevErroNum++; // reception error message number adds 1

/*

Receive the baud rate that continuous 6 wrong messages reset serial ports

*/

if(ASCRevErroNum>5)

{

BaudrateInde++;

BaudrateInde%=12;

ASC_Baudrate(ASC_Baudrate_Const【BaudrateInde】；

}

return;

}

/*

Carry out normal MODBUS handling process

*/

if(pAsc->pRxSem)

{

OSMboxPost(pAsc->pRxSem,&Asc1RxMsg);

}

ASCRevErroNum=0；

return;

}

}

void ASC_Baudrate_ (__word32 TheBaudrate,)

{

USART_InitTypeDef USART_InitStructure;

USART_InitStructure.USART_WordLength=USART_WordLength_8b; // 8 bit data positions

USART_InitStructure.USART_StopBits=USART_StopBits_1; // 1 position of rest

USART_InitStructure.USART_Parity=USART_Parity_No; // no parity

SART_InitStructure.USART_HardwareFlowControl=USART_HardwareFlowControl_None; // without data flow con-trol

USART_InitStructure.USART_Mode=USART_Mode_Rx | USART_Mode_Tx; // enable send and receive

USART_InitStructure.USART_BaudRate=TheBaudrate; Baud rate is set

USART_Init (USART2, & USART_InitStructure); Initialization serial ports

Enabling corresponding serial ports interrupts

USART_ITConfig(USART2,USART_IT_TC,DISABLE);

USART_ITConfig(USART2,USART_IT_RXNE,DISABLE);

USART_ITConfig(USART2,USART_IT_TXE ,DISABLE);

USART_ITConfig(USART2,USART_IT_IDLE,ENABLE);

USART_Cmd (USART2, ENABLE); Enable serial ports

}。

Claims (1)

1.MODBUS-RTU communication baud rate Auto-matching, it is characterized in that, its implementation procedure is as follows: the baud rate that serial ports is set when 1. slave station powers on is the baud rate of acquiescence, wait for the serial ports message receiving in bus, if the continuous message receiving for 5 times is error message, just to reset serial ports baud rate be the next baud rate that master-salve station is better, until while correctly receiving serial ports message, just with this baud rate and master station communication; 2. the in the situation that of proper communication, main website has changed baud rate, whether the message the standing-meeting bus that detection receives in real time is correct, if continuous 5 times receive error message, repeat baud rate matching process, until receive correct message, whether correctly the message that slave station the receives data format of basis for estimation MODBUS communication protocol carries out verification, main check (CRC) check code, whole message length.