freemodbus教程之freemodbus移植应用串口中断接收和数据解析

inr999 2021-02-18 7912

接口/总线/驱动

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描述

本篇主要讲解从机数据的接收流程。接收流程分为两个阶段：串口中断接收和数据解析。

第一阶段：中断接收函数prvvUARTRxISR（xMBRTUReceiveFSM）和定时器中断回调函数xMBRTUtimerT35Expired（），

第二阶段：数据解析eMBPoll( )。

一、串口中断接收

　　从机正常状态下，串口设置为接收中断模式，也不启动定时器。当检测到有数据时，中断函数调用xMBRTUReceiveFSM（）函数，通过该函数中的ucRTUBuf数组存储接收帧，用usRcvBufferPos存储数据帧长度。具体函数：

1、中断接收函数。

void UART1_IRQ(void)

{

IF(USART_GetITStatus(USART1,USART_IT_TXE))

{

pxMBFrameCBTransmitterEmpty( );

}

else if(USART_GetITStatus(USART1,USART_IT_RXNE))//接收中断

{

pxMBFrameCBByteReceived( );//pxMBFrameCBByteReceived = xMBRTUReceiveFSM;

}

2、xMBRTUReceiveFSM（）函数。RTU接收状态函数。只要进人该函数，就会启动定时器中断。

　　从机的接收状态：

　　　　　（１）STATE_RX_INIT（协议栈初始化）；

（2）STATE_RX_ERROR（接收错误）；　

（3）STATE_RX_IDLE（接收空闲，接收帧头，常用）；

（4）STATE_RX_RCV（接收所有数据，常用）。

　　注意：接收数据时，只要接收到数据，定时器就会清零，重新计数。

BOOL

xMBRTUReceiveFSM( void )

{

BOOL xTaskNeedSwitch = FALSE;

UCHAR ucByte;

assert( eSndState == STATE_TX_IDLE );

/* Always read the character. */

( void )xMBPortSerialGetByte( ( CHAR * ) & ucByte );

switch ( eRcvState )

{

/* If we have received a character in the init state we have to

* wait until the frame is finished.

case STATE_RX_INIT:

vMBPortTimersEnable( );

break;

/* In the error state we wait until all characters in the

* damaged frame are transmitted.

case STATE_RX_ERROR:

vMBPortTimersEnable( );

break;

/* In the idle state we wait for a new character. If a character

* is received the t1.5 and t3.5 timers are started and the

* receiver is in the state STATE_RX_RECEIVCE.

case STATE_RX_IDLE:

usRcvBufferPos = 0;

ucRTUBuf[usRcvBufferPos++] = ucByte;

eRcvState = STATE_RX_RCV;

/* Enable t3.5 timers. */

vMBPortTimersEnable( );

break;

/* We are currently receiving a frame. Reset the timer after

* every character received. If more than the maximum possible

* number of bytes in a modbus frame is received the frame is

* ignored.

case STATE_RX_RCV:

if( usRcvBufferPos < MB_SER_PDU_SIZE_MAX )

{

ucRTUBuf[usRcvBufferPos++] = ucByte;

}

else

{

eRcvState = STATE_RX_ERROR;

}

vMBPortTimersEnable( );

break;

}

return xTaskNeedSwitch;

}

二、数据解析

涉及到的函数 eMBPoll、eMBRTUReceive和xFuncHandlers[i]是结构体数组。

1、eMBPoll函数。eMBPoll函数调用eMBRTUReceive和xFuncHandlers[i]结构体数组。

eMBErrorCode

eMBPoll( void )

{

static UCHAR *ucMBFrame;

static UCHAR ucRcvAddress;

static UCHAR ucFunctionCode;

static USHORT usLength;

static eMBException eException;

int i;

eMBErrorCode eStatus = MB_ENOERR;

eMBEventType eEvent;

/* Check if the protocol stack is ready. */

if( eMBState != STATE_ENABLED )

{

return MB_EILLSTATE;

}

/* Check if there is a event available. If not return control to caller.

* Otherwise we will handle the event. */

if( xMBPortEventGet( &eEvent ) == TRUE )

{

switch ( eEvent )

{

case EV_READY:

break;

case EV_FRAME_RECEIVED:

eStatus = peMBFrameReceiveCur( &ucRcvAddress, &ucMBFrame, &usLength );

if( eStatus == MB_ENOERR )

{

/* Check if the frame is for us. If not ignore the frame. */

if( ( ucRcvAddress == ucMBAddress ) || ( ucRcvAddress == MB_ADDRESS_BROADCAST ) )

{

( void )xMBPortEventPost( EV_EXECUTE );

}

break;

case EV_EXECUTE:

ucFunctionCode = ucMBFrame[MB_PDU_FUNC_OFF];//把接收的数据传递给ucFunctionCode

eException = MB_EX_ILLEGAL_FUNCTION;

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

{

/* No more function handlers registered. Abort. */

if( xFuncHandlers[i].ucFunctionCode == 0 )

{

break;

}

else if( xFuncHandlers[i].ucFunctionCode == ucFunctionCode )//查询匹配的功能码，

{

eException = xFuncHandlers[i].pxHandler( ucMBFrame, &usLength );//调用相应的功能函数

break;

}

/* If the request was not sent to the broadcast address we

* return a reply. */

if( ucRcvAddress != MB_ADDRESS_BROADCAST )

{

if( eException != MB_EX_NONE )//如果接收有问题

{

/* An exception occured. Build an error frame. */

usLength = 0;

ucMBFrame[usLength++] = ( UCHAR )( ucFunctionCode | MB_FUNC_ERROR );//功能码与0x80或之后的为 //异常码

ucMBFrame[usLength++] = eException;//非法功能代码

}

if( ( eMBCurrentMode == MB_ASCII ) && MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS )

{

vMBPortTimersDelay( MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS );

}

eStatus = peMBFrameSendCur( ucMBAddress, ucMBFrame, usLength );//发送数据

}

break;

case EV_FRAME_SENT:

break;

}

return MB_ENOERR;

}

2、peMBFrameReceiveCur（） //数据帧接收函数指针

3、主要讲一下xFuncHandlers[i]，它是结构体数组，存放的是功能码以及对应的报文解析函数。

typedef struct { UCHAR ucFunctionCode; pxMBFunctionHandler pxHandler; } xMBFunctionHandler;

static xMBFunctionHandler xFuncHandlers[MB_FUNC_HANDLERS_MAX] = {

#if MB_FUNC_OTHER_REP_SLAVEID_ENABLED > 0

{MB_FUNC_OTHER_REPORT_SLAVEID, eMBFuncReportSlaveID},

#endif

#if MB_FUNC_READ_INPUT_ENABLED > 0

{MB_FUNC_READ_INPUT_REGISTER, eMBFuncReadInputRegister},

#endif

#if MB_FUNC_READ_HOLDING_ENABLED > 0

{MB_FUNC_READ_HOLDING_REGISTER, eMBFuncReadHoldingRegister},

#endif

#if MB_FUNC_WRITE_MULTIPLE_HOLDING_ENABLED > 0

{MB_FUNC_WRITE_MULTIPLE_REGISTERS, eMBFuncWriteMultipleHoldingRegister},

#endif

#if MB_FUNC_WRITE_HOLDING_ENABLED > 0

{MB_FUNC_WRITE_REGISTER, eMBFuncWriteHoldingRegister},

#endif

#if MB_FUNC_READWRITE_HOLDING_ENABLED > 0

{MB_FUNC_READWRITE_MULTIPLE_REGISTERS, eMBFuncReadWriteMultipleHoldingRegister},

#endif

#if MB_FUNC_READ_COILS_ENABLED > 0

{MB_FUNC_READ_COILS, eMBFuncReadCoils},

#endif

#if MB_FUNC_WRITE_COIL_ENABLED > 0

{MB_FUNC_WRITE_SINGLE_COIL, eMBFuncWriteCoil},

#endif

#if MB_FUNC_WRITE_MULTIPLE_COILS_ENABLED > 0

{MB_FUNC_WRITE_MULTIPLE_COILS, eMBFuncWriteMultipleCoils},

#endif

#if MB_FUNC_READ_DISCRETE_INPUTS_ENABLED > 0

{MB_FUNC_READ_DISCRETE_INPUTS, eMBFuncReadDiscreteInputs},

#endif

};

以功能码04为例，读取输入寄存器。

eMBException

eMBFuncReadInputRegister( UCHAR * pucFrame, USHORT * usLen )

{

USHORT usRegAddress;

USHORT usRegCount;

UCHAR *pucFrameCur;

eMBException eStatus = MB_EX_NONE;

eMBErrorCode eRegStatus;

if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )//计算帧长度，除了地址位和两位的crc校验位

{

usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );//读取寄存器的首地址

usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );

usRegAddress++;

usRegCount = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_REGCNT_OFF] << 8 );//计算读取寄存器的长度

usRegCount |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_REGCNT_OFF + 1] );

/* Check if the number of registers to read is valid. If not

* return Modbus illegal data value exception.

if( ( usRegCount >= 1 )

&& ( usRegCount < MB_PDU_FUNC_READ_REGCNT_MAX ) )//读取寄存器的长度不越界

{

/* Set the current PDU data pointer to the beginning. */

pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];//把数据帧赋值给pucFrameCur

*usLen = MB_PDU_FUNC_OFF;

/* First byte contains the function code. */

*pucFrameCur++ = MB_FUNC_READ_INPUT_REGISTER;//

*usLen += 1;

/* Second byte in the response contain the number of bytes. */

*pucFrameCur++ = ( UCHAR )( usRegCount * 2 );

*usLen += 1;

eRegStatus =

eMBRegInputCB( pucFrameCur, usRegAddress, usRegCount );

/* If an error occured convert it into a Modbus exception. */

if( eRegStatus != MB_ENOERR )

{

eStatus = prveMBError2Exception( eRegStatus );

}

else

{

*usLen += usRegCount * 2;

}

else

{

eStatus = MB_EX_ILLEGAL_DATA_VALUE;

}

else

{

/* Can't be a valid read input register request because the length

* is incorrect. */

eStatus = MB_EX_ILLEGAL_DATA_VALUE;

}

return eStatus;

}

eMBErrorCode

eMBRegInputCB( UCHAR * pucRegBuffer, USHORT usAddress, USHORT usNRegs )

{

eMBErrorCode eStatus = MB_ENOERR;

int iRegIndex;

if( ( usAddress >= REG_INPUT_START )

&& ( usAddress + usNRegs <= REG_INPUT_START + REG_INPUT_NREGS ) )

{

iRegIndex = ( int )( usAddress - REG_INPUT_START );

while( usNRegs > 0 )

{

*pucRegBuffer++ =

( unsigned char )( usRegInputBuf[iRegIndex] >> 8 );

*pucRegBuffer++ =

( unsigned char )( usRegInputBuf[iRegIndex] & 0xFF );

iRegIndex++;

usNRegs--;

}

else

{

eStatus = MB_ENOREG;

}

return eStatus;

}

以上就是整个接收数据、解析数据的过程。

来源：csdn博客萧年已逝；在此特别鸣谢！

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