lightmodbus.h File Reference

Core Modbus functions. More...

Go to the source code of this file.

Typedefs
typedef enum modbusError	ModbusError
	Represents a library runtime error code. More...
typedef enum modbusFrameError	ModbusFrameError
	Provides more information on frame building/parsing error. More...
typedef enum modbusExceptionCode	ModbusExceptionCode
	Represents a Modbus exception code, defined by the standart. More...
typedef enum modbusDataType	ModbusDataType
	Stores information about Modbus data types. More...

Enumerations
enum	modbusError {   MODBUS_ERROR_OK = 0, MODBUS_ERROR_EXCEPTION = 1, MODBUS_ERROR_ALLOC, MODBUS_ERROR_OTHER,   MODBUS_ERROR_NULLPTR, MODBUS_ERROR_PARSE, MODBUS_ERROR_BUILD, MODBUS_OK = MODBUS_ERROR_OK }
	Represents a library runtime error code. More...
enum	modbusFrameError {   MODBUS_FERROR_OK = MODBUS_OK, MODBUS_FERROR_CRC, MODBUS_FERROR_LENGTH, MODBUS_FERROR_COUNT,   MODBUS_FERROR_VALUE, MODBUS_FERROR_RANGE, MODBUS_FERROR_NOSRC, MODBUS_FERROR_NOREAD,   MODBUS_FERROR_NOWRITE, MODBUS_FERROR_NOFUN, MODBUS_FERROR_BADFUN, MODBUS_FERROR_NULLFUN,   MODBUS_FERROR_MISM_FUN, MODBUS_FERROR_MISM_ADDR, MODBUS_FERROR_MISM_INDEX, MODBUS_FERROR_MISM_COUNT,   MODBUS_FERROR_MISM_VALUE, MODBUS_FERROR_MISM_MASK, MODBUS_FERROR_BROADCAST }
	Provides more information on frame building/parsing error. More...
enum	modbusExceptionCode {   MODBUS_EXCEP_ILLEGAL_FUNCTION = 1, MODBUS_EXCEP_ILLEGAL_ADDRESS = 2, MODBUS_EXCEP_ILLEGAL_VALUE = 3, MODBUS_EXCEP_SLAVE_FAILURE = 4,   MODBUS_EXCEP_ACK = 5, MODBUS_EXCEP_NACK = 7 }
	Represents a Modbus exception code, defined by the standart. More...
enum	modbusDataType { MODBUS_HOLDING_REGISTER = 1, MODBUS_INPUT_REGISTER = 2, MODBUS_COIL = 4, MODBUS_DISCRETE_INPUT = 8 }
	Stores information about Modbus data types. More...

Functions
static uint16_t	modbusBitsToBytes (uint16_t n)
	Converts number of bits to number of bytes required to store them. More...
static uint16_t	modbusSwapEndian (uint16_t data)
	Swaps endianness of provided 16-bit data portion. More...
static uint16_t	modbusMatchEndian (uint16_t data)
	Swaps endianness of provided 16-bit data portion if needed. More...
uint8_t	modbusMaskRead (const uint8_t *mask, uint16_t maskLength, uint16_t bit)
	Reads n-th bit from an array. More...
uint8_t	modbusMaskWrite (uint8_t *mask, uint16_t maskLength, uint16_t bit, uint8_t value)
	Writes n-th bit in an array. More...
uint16_t	modbusCRC (const uint8_t *data, uint16_t length)
	Calculates 16-bit Modbus CRC of provided data. More...

Detailed Description

Core Modbus functions.

This is main header file that is ought to be included as library

Note

This header file is suitable for C++

Typedef Documentation

ModbusDataType

typedef enum modbusDataType ModbusDataType

Stores information about Modbus data types.

ModbusError

typedef enum modbusError ModbusError

Represents a library runtime error code.

ModbusExceptionCode

typedef enum modbusExceptionCode ModbusExceptionCode

Represents a Modbus exception code, defined by the standart.

ModbusFrameError

typedef enum modbusFrameError ModbusFrameError

Provides more information on frame building/parsing error.

These error code should serve as an additional source of information for the user.

Enumeration Type Documentation

modbusDataType

enum modbusDataType

Stores information about Modbus data types.

Enumerator
MODBUS_HOLDING_REGISTER	Holding register.
MODBUS_INPUT_REGISTER	Input register.
MODBUS_COIL	Coil.
MODBUS_DISCRETE_INPUT	Discrete input.

modbusError

enum modbusError

Represents a library runtime error code.

Enumerator
MODBUS_ERROR_OK	No error.
MODBUS_ERROR_EXCEPTION	Indicates that slave had thrown an exception. This exception can be thrown either by master's parsing function (indicating incoming exception frame) or by slave's building function (indicating that some problem caused the slave to build an exception frame). Note This error code handles the superset of problems handled by MODBUS_ERROR_PARSE. When thrown on slave side, check ModbusSlave::lastException and ModbusSlave::parseError for more information.
MODBUS_ERROR_ALLOC	Memory problem. Either one of memory allocation functions returned NULL or fixed-size buffer is not big enough to fit the data (see Disabling dynamic memory allocation).Memory allocation problem
MODBUS_ERROR_OTHER	Other reason causing the function to abort (eg. bad function parameter)
MODBUS_ERROR_NULLPTR	A NULL pointer provided as some crucial parameter.
MODBUS_ERROR_PARSE	Parsing error occurred - check ModbusSlave::parseError Note This error code is returned instead of MODBUS_ERROR_EXCEPTION when exception should have been thrown, but wasn't (eg. due to broadcasted request frame). These two error code should be treated similarly.
MODBUS_ERROR_BUILD	Frame building error occurred - check ModbusMaster::buildError.
MODBUS_OK	No error. Alias of MODBUS_ERROR_OK.

modbusExceptionCode

enum modbusExceptionCode

Represents a Modbus exception code, defined by the standart.

Enumerator
MODBUS_EXCEP_ILLEGAL_FUNCTION	Illegal function code.
MODBUS_EXCEP_ILLEGAL_ADDRESS	Illegal data address.
MODBUS_EXCEP_ILLEGAL_VALUE	Illegal data value.
MODBUS_EXCEP_SLAVE_FAILURE	Slave could not process the request.
MODBUS_EXCEP_ACK	Acknowledge.
MODBUS_EXCEP_NACK	Negative acknowledge.

modbusFrameError

enum modbusFrameError

Provides more information on frame building/parsing error.

These error code should serve as an additional source of information for the user.

Enumerator
MODBUS_FERROR_OK	Modbus frame OK. No error.
MODBUS_FERROR_CRC	Invalid CRC.
MODBUS_FERROR_LENGTH	Invalid frame length.
MODBUS_FERROR_COUNT	Invalid declared data item count.
MODBUS_FERROR_VALUE	Illegal data value (eg. when writing a single coil)
MODBUS_FERROR_RANGE	Invalid register range.
MODBUS_FERROR_NOSRC	There's neither callback function nor value array provided for this data type.
MODBUS_FERROR_NOREAD	No read access to at least one of requested regsiters.
MODBUS_FERROR_NOWRITE	No write access to one of requested regsiters.
MODBUS_FERROR_NOFUN	Function not supported.
MODBUS_FERROR_BADFUN	Requested a parsing function to parse a frame with wrong function code.
MODBUS_FERROR_NULLFUN	Function overriden by user with NULL pointer.
MODBUS_FERROR_MISM_FUN	Function request-response mismatch.
MODBUS_FERROR_MISM_ADDR	Slave address request-response mismatch.
MODBUS_FERROR_MISM_INDEX	Index value request-response mismatch.
MODBUS_FERROR_MISM_COUNT	Count value request-response mismatch.
MODBUS_FERROR_MISM_VALUE	Data value request-response mismatch.
MODBUS_FERROR_MISM_MASK	Mask value request-response mismatch.
MODBUS_FERROR_BROADCAST	Received response for broadcast message.

Function Documentation

modbusBitsToBytes()

static uint16_t modbusBitsToBytes ( uint16_t  n )

inlinestatic

Converts number of bits to number of bytes required to store them.

Parameters

n	Number of bits

Returns

Number of bytes of required memory

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modbusCRC()

uint16_t modbusCRC	(	const uint8_t *	data,
		uint16_t	length
	)

Calculates 16-bit Modbus CRC of provided data.

Parameters

data	A pointer to the data to be processed
length	Number of bytes, starting at the data pointer, to process

Returns

16-bit Modbus CRC value

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modbusMaskRead()

uint8_t modbusMaskRead	(	const uint8_t *	mask,
		uint16_t	maskLength,
		uint16_t	bit
	)

Reads n-th bit from an array.

Parameters

mask	A pointer to the array
maskLength	The length of the array in bytes
bit	Number of the bit to be read

Returns

The bit value, or 255 if the bit lies outside the array.

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modbusMaskWrite()

uint8_t modbusMaskWrite	(	uint8_t *	mask,
		uint16_t	maskLength,
		uint16_t	bit,
		uint8_t	value
	)

Writes n-th bit in an array.

Parameters

mask	A pointer to the array
maskLength	The length of the array in bytes
bit	Number of the bit to write
value	Bit value to be written

Returns

Bit value on success, 255 if the bit lies outside the array.

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modbusMatchEndian()

static uint16_t modbusMatchEndian ( uint16_t  data )

inlinestatic

Swaps endianness of provided 16-bit data portion if needed.

Note

This function works only if the system is not big-endian

Parameters

data	A 16-bit data portion.

Returns

The same data, but with bytes swapped if the system is little-endian

See also

modbusSwapEndian

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modbusSwapEndian()

static uint16_t modbusSwapEndian ( uint16_t  data )

inlinestatic

Swaps endianness of provided 16-bit data portion.

Note

This function, unlike modbusMatchEndian, works unconditionally

Parameters

data	A 16-bit data portion.

Returns

The same data, but with bytes swapped

See also

modbusMatchEndian

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