Common types and functions (header) More...

#include <stdint.h>

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Data Structures
struct	ModbusErrorInfo
	Richer error represenation - source and type of error. More...

struct	ModbusBuffer
	Stores a Modbus frame. More...

Macros
#define	LIGHTMODBUS_WARN_UNUSED __attribute__((warn_unused_result))

#define	LIGHTMODBUS_ALWAYS_INLINE __attribute__((always_inline))

#define	MODBUS_PDU_MIN 1
	Minimum length of a PDU.

#define	MODBUS_PDU_MAX 253
	Maximum length of a PDU.

#define	MODBUS_RTU_ADU_MIN 4
	Minimum length of ADU in Modbus RTU.

#define	MODBUS_RTU_ADU_MAX 256
	Maximum length of ADU in Modbus RTU.

#define	MODBUS_RTU_ADU_PADDING 3
	Number of extra bytes added to the PDU in Modbus RTU.

#define	MODBUS_RTU_PDU_OFFSET 1
	Offset of PDU relative to the frame beginning in Modbus RTU.

#define	MODBUS_TCP_ADU_MIN 8
	Minimum length of ADU in Modbus TCP.

#define	MODBUS_TCP_ADU_MAX 260
	Maximum length of ADU in Modbus TCP.

#define	MODBUS_TCP_ADU_PADDING 7
	Number of extra bytes added to the PDU in Modbus TCP.

#define	MODBUS_TCP_PDU_OFFSET 7
	Offset of PDU relative to the frame beginning in Modbus TCP.

#define	LIGHTMODBUS_RET_ERROR LIGHTMODBUS_WARN_UNUSED ModbusErrorInfo
	Return type for library functions returning ModbusErrorInfo that should be handled properly.

#define	MODBUS_ERROR_SOURCE_GENERAL 0u
	General library error - can be caused by providing an incorrect argument or a internal library error.

#define	MODBUS_ERROR_SOURCE_REQUEST 1u
	The request frame contains errors.

#define	MODBUS_ERROR_SOURCE_RESPONSE 2u
	The response frame contains errors.

#define	MODBUS_ERROR_SOURCE_RESERVED 3u
	Reserved for future use.

#define	MODBUS_MAKE_ERROR(s, e) ((ModbusErrorInfo){.source = (s), .error = (e)})
	Constructs a ModbusErrorInfo object from a ModbusErrorCode and a `MODBUS_ERROR_SOURCE_*` macro.

#define	MODBUS_NO_ERROR() MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_GENERAL, MODBUS_OK)
	Construcs a ModbusErrorInfo object for which `modbusIsOK()` is guaranteed to return true.

#define	MODBUS_GENERAL_ERROR(e) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_GENERAL, (MODBUS_ERROR_##e))
	Constructs a ModbusErrorInfo where source is set to `MODBUS_ERROR_SOURCE_GENERAL` and the error code is set to `MODBUS_ERROR_##e`.

#define	MODBUS_REQUEST_ERROR(e) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_REQUEST, (MODBUS_ERROR_##e))
	Constructs a ModbusErrorInfo where source is set to `MODBUS_ERROR_SOURCE_REQUESTL` and the error code is set to `MODBUS_ERROR_##e`.

#define	MODBUS_RESPONSE_ERROR(e) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_RESPONSE, (MODBUS_ERROR_##e))
	Constructs a ModbusErrorInfo where source is set to `MODBUS_ERROR_SOURCE_RESPONSE` and the error code is set to `MODBUS_ERROR_##e`.

Typedefs
typedef struct ModbusErrorInfo	ModbusErrorInfo
	Richer error represenation - source and type of error.

typedef enum ModbusError	ModbusError
	Represtents different kinds of errors.

typedef enum ModbusExceptionCode	ModbusExceptionCode
	Represents a Modbus exception code.

typedef enum ModbusDataType	ModbusDataType
	Represents different Modbus data types.

typedef ModbusError(*	ModbusAllocator) (struct ModbusBuffer buffer, uint16_t size, void context)
	Pointer to a memory allocator function.

typedef struct ModbusBuffer	ModbusBuffer
	Stores a Modbus frame.

Enumerations
enum	ModbusError { MODBUS_OK = 0 , MODBUS_ERROR_OK = 0 , MODBUS_ERROR_LENGTH , MODBUS_ERROR_ALLOC , MODBUS_ERROR_FUNCTION , MODBUS_ERROR_COUNT , MODBUS_ERROR_INDEX , MODBUS_ERROR_VALUE , MODBUS_ERROR_RANGE , MODBUS_ERROR_CRC , MODBUS_ERROR_BAD_PROTOCOL , MODBUS_ERROR_BAD_TRANSACTION , MODBUS_ERROR_ADDRESS , MODBUS_ERROR_OTHER }
	Represtents different kinds of errors. More...

enum	ModbusExceptionCode { MODBUS_EXCEP_NONE = 0 , 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. More...

enum	ModbusDataType { MODBUS_HOLDING_REGISTER = 1 , MODBUS_INPUT_REGISTER = 2 , MODBUS_COIL = 4 , MODBUS_DISCRETE_INPUT = 8 }
	Represents different Modbus data types. More...

Functions
ModbusError	modbusDefaultAllocator (ModbusBuffer buffer, uint16_t size, void context)
	The default memory allocator based on realloc()

ModbusErrorInfo	modbusBufferInit (ModbusBuffer *buffer, ModbusAllocator allocator)
	Initializes a buffer for use.

void	modbusBufferDestroy (ModbusBuffer buffer, void context)
	Equivalent of modbusBufferFree() \copydetail modbusBufferFree()

ModbusError	modbusBufferAllocateADU (ModbusBuffer buffer, uint16_t pduSize, void context)
	Allocates memory to hold Modbus ADU.

void	modbusBufferFree (ModbusBuffer buffer, void context)
	Frees memory allocated inside the buffer.

uint16_t	modbusCRC (const uint8_t *data, uint16_t length)
	Calculates 16-bit Modbus CRC of provided data.

static void	modbusBufferModePDU (ModbusBuffer *buffer)
	Prepares buffer to only store a Modbus PDU.

static void	modbusBufferModeRTU (ModbusBuffer *buffer)
	Prepares buffer to store a Modbus RTU message.

static void	modbusBufferModeTCP (ModbusBuffer *buffer)
	Prepares buffer to store a Modbus TCP message.

static uint8_t	modbusMaskRead (const uint8_t *mask, uint16_t n)
	Reads n-th bit from an array.

static void	modbusMaskWrite (uint8_t *mask, uint16_t n, uint8_t value)
	Writes n-th bit in an array.

static uint16_t	modbusBitsToBytes (uint16_t n)
	Returns number of bytes necessary to hold given number of bits.

static uint16_t	modbusRLE (const uint8_t *p)
	Safely reads a little-endian 16-bit word from provided pointer.

static uint16_t	modbusWLE (uint8_t *p, uint16_t val)
	Safely writes a little-endian 16-bit word to provided pointer.

static uint16_t	modbusRBE (const uint8_t *p)
	Safely reads a big-endian 16-bit word from provided pointer.

static uint16_t	modbusWBE (uint8_t *p, uint16_t val)
	Safely writes a big-endian 16-bit word to provided pointer.

static uint8_t	modbusCheckRangeU16 (uint16_t index, uint16_t count)
	Checks whether provided address range causes an `uint16_t` overflow.

static uint8_t	modbusGetErrorSource (ModbusErrorInfo err)
	Returns uint8_t describing error source of ModbusErrorInfo.

static ModbusError	modbusGetErrorCode (ModbusErrorInfo err)
	Returns ModbusError contained in ModbusErrorInfo.

static uint8_t	modbusIsOk (ModbusErrorInfo err)
	Checks if ModbusErrorInfo contains an error.

static ModbusError	modbusGetGeneralError (ModbusErrorInfo err)
	Returns general error from ModbusErrorInfo.

static ModbusError	modbusGetRequestError (ModbusErrorInfo err)
	Returns request error from ModbusErrorInfo.

static ModbusError	modbusGetResponseError (ModbusErrorInfo err)
	Returns response error from ModbusErrorInfo.

static ModbusError	modbusUnpackRTU (const uint8_t frame, uint16_t length, uint8_t checkCRC, const uint8_t pdu, uint16_t pduLength, uint8_t *address)
	Unpacks data from a Modbus RTU frame and optionally checks CRC.

static ModbusError	modbusPackRTU (uint8_t *frame, uint16_t length, uint8_t address)
	Sets up address and CRC in a Modbus RTU frame.

static ModbusError	modbusUnpackTCP (const uint8_t frame, uint16_t length, const uint8_t pdu, uint16_t pduLength, uint16_t transactionID, uint8_t unitID)
	Unpacks data from a Modbus TCP frame.

static ModbusError	modbusPackTCP (uint8_t *frame, uint16_t length, uint16_t transactionID, uint8_t unitID)
	Sets up the MBAP header in a Modbus TCP frame.

Detailed Description

Common types and functions (header)

Macro Definition Documentation

◆ LIGHTMODBUS_ALWAYS_INLINE

#define LIGHTMODBUS_ALWAYS_INLINE __attribute__((always_inline))

◆ LIGHTMODBUS_RET_ERROR

#define LIGHTMODBUS_RET_ERROR LIGHTMODBUS_WARN_UNUSED ModbusErrorInfo

Return type for library functions returning ModbusErrorInfo that should be handled properly.

◆ LIGHTMODBUS_WARN_UNUSED

#define LIGHTMODBUS_WARN_UNUSED __attribute__((warn_unused_result))

◆ MODBUS_ERROR_SOURCE_GENERAL

#define MODBUS_ERROR_SOURCE_GENERAL 0u

General library error - can be caused by providing an incorrect argument or a internal library error.

◆ MODBUS_ERROR_SOURCE_REQUEST

#define MODBUS_ERROR_SOURCE_REQUEST 1u

The request frame contains errors.

◆ MODBUS_ERROR_SOURCE_RESERVED

#define MODBUS_ERROR_SOURCE_RESERVED 3u

Reserved for future use.

◆ MODBUS_ERROR_SOURCE_RESPONSE

#define MODBUS_ERROR_SOURCE_RESPONSE 2u

The response frame contains errors.

◆ MODBUS_GENERAL_ERROR

#define MODBUS_GENERAL_ERROR ( e ) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_GENERAL, (MODBUS_ERROR_##e))

Constructs a ModbusErrorInfo where source is set to MODBUS_ERROR_SOURCE_GENERAL and the error code is set to MODBUS_ERROR_##e.

◆ MODBUS_MAKE_ERROR

#define MODBUS_MAKE_ERROR	(	s,
		e
	)	((ModbusErrorInfo){.source = (s), .error = (e)})

Constructs a ModbusErrorInfo object from a ModbusErrorCode and a MODBUS_ERROR_SOURCE_* macro.

◆ MODBUS_NO_ERROR

#define MODBUS_NO_ERROR ( ) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_GENERAL, MODBUS_OK)

Construcs a ModbusErrorInfo object for which modbusIsOK() is guaranteed to return true.

◆ MODBUS_PDU_MAX

#define MODBUS_PDU_MAX 253

Maximum length of a PDU.

◆ MODBUS_PDU_MIN

#define MODBUS_PDU_MIN 1

Minimum length of a PDU.

◆ MODBUS_REQUEST_ERROR

#define MODBUS_REQUEST_ERROR ( e ) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_REQUEST, (MODBUS_ERROR_##e))

Constructs a ModbusErrorInfo where source is set to MODBUS_ERROR_SOURCE_REQUESTL and the error code is set to MODBUS_ERROR_##e.

◆ MODBUS_RESPONSE_ERROR

#define MODBUS_RESPONSE_ERROR ( e ) MODBUS_MAKE_ERROR(MODBUS_ERROR_SOURCE_RESPONSE, (MODBUS_ERROR_##e))

Constructs a ModbusErrorInfo where source is set to MODBUS_ERROR_SOURCE_RESPONSE and the error code is set to MODBUS_ERROR_##e.

◆ MODBUS_RTU_ADU_MAX

#define MODBUS_RTU_ADU_MAX 256

Maximum length of ADU in Modbus RTU.

◆ MODBUS_RTU_ADU_MIN

#define MODBUS_RTU_ADU_MIN 4

Minimum length of ADU in Modbus RTU.

◆ MODBUS_RTU_ADU_PADDING

#define MODBUS_RTU_ADU_PADDING 3

Number of extra bytes added to the PDU in Modbus RTU.

◆ MODBUS_RTU_PDU_OFFSET

#define MODBUS_RTU_PDU_OFFSET 1

Offset of PDU relative to the frame beginning in Modbus RTU.

◆ MODBUS_TCP_ADU_MAX

#define MODBUS_TCP_ADU_MAX 260

Maximum length of ADU in Modbus TCP.

◆ MODBUS_TCP_ADU_MIN

#define MODBUS_TCP_ADU_MIN 8

Minimum length of ADU in Modbus TCP.

◆ MODBUS_TCP_ADU_PADDING

#define MODBUS_TCP_ADU_PADDING 7

Number of extra bytes added to the PDU in Modbus TCP.

◆ MODBUS_TCP_PDU_OFFSET

#define MODBUS_TCP_PDU_OFFSET 7

Offset of PDU relative to the frame beginning in Modbus TCP.

Typedef Documentation

◆ ModbusAllocator

typedef ModbusError(* ModbusAllocator) (struct ModbusBuffer *buffer, uint16_t size, void *context)

Pointer to a memory allocator function.

Please refer to Custom allocators for more information regarding custom allocator functions.

◆ ModbusBuffer

typedef struct ModbusBuffer ModbusBuffer

Stores a Modbus frame.

See also: modbusBufferInit(); modbusBufferDestroy(); modbusBufferModePDU(); modbusBufferModeRTU(); modbusBufferModeTCP(); modbusBufferAllocateADU(); modbusBufferFree()

◆ ModbusDataType

typedef enum ModbusDataType ModbusDataType

Represents different Modbus data types.

◆ ModbusError

typedef enum ModbusError ModbusError

Represtents different kinds of errors.

See also: ModbusErrorInfo

◆ ModbusErrorInfo

typedef struct ModbusErrorInfo ModbusErrorInfo

Richer error represenation - source and type of error.

See also: ModbusError; modbusIsOk(); modbusGetGeneralError(); modbusGetRequestError(); modbusGetResponseError(); modbusGetErrorSource(); modbusGetErrorCode()

Warning: You should not be accessing source and error directly. The internal implementation of this struct may change in future releases. For this reason, please use modbusGetGeneralError(), modbusGetRequestError(), modbusGetResponseError(), modbusGetErrorSource() and modbusIsOk() instead.

◆ ModbusExceptionCode

typedef enum ModbusExceptionCode ModbusExceptionCode

Represents a Modbus exception code.

Enumeration Type Documentation

◆ ModbusDataType

enum ModbusDataType

Represents different 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

Represtents different kinds of errors.

See also: ModbusErrorInfo

Enumerator
MODBUS_OK	No error. Returned when everything is fine.
MODBUS_ERROR_OK	Same as MODBUS_OK.
MODBUS_ERROR_LENGTH	Invalid frame length. The provided frame is either too long or too short The data length declared in frame does not match the actual frame length
MODBUS_ERROR_ALLOC	Memory allocation error. The allocator has failed to allocate requested amount of memory or free it.
MODBUS_ERROR_FUNCTION	Invalid function.
MODBUS_ERROR_COUNT	Invalid register count. Provided register count is 0 or exceeds maximum allowed value.
MODBUS_ERROR_INDEX	Invalid index value.
MODBUS_ERROR_VALUE	Invalid register value.
MODBUS_ERROR_RANGE	Invalid register range. Returned when accessing `count` registers starting at `index` would cause a 16-bit unsigned int overflow.
MODBUS_ERROR_CRC	CRC invalid. Note Only in Modbus RTU
MODBUS_ERROR_BAD_PROTOCOL	Invalid protocol ID (nonzero) Note Only in Modbus TCP
MODBUS_ERROR_BAD_TRANSACTION	Mismatched transaction ID. Note Only in Modbus TCP The transaction identifier in the response does not match the one in the request frame.
MODBUS_ERROR_ADDRESS	Invalid slave address.
MODBUS_ERROR_OTHER	Other error.

◆ ModbusExceptionCode

enum ModbusExceptionCode

Represents a Modbus exception code.

Enumerator
MODBUS_EXCEP_NONE
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.

Function Documentation

◆ modbusBitsToBytes()

static uint16_t modbusBitsToBytes ( uint16_t n )

inlinestatic

Returns number of bytes necessary to hold given number of bits.

Parameters

n	Number of bits

Returns: Number of bytes requred to hold n bits

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◆ modbusBufferAllocateADU()

ModbusError modbusBufferAllocateADU	(	ModbusBuffer *	buffer,
		uint16_t	pduSize,
		void *	context
	)

Allocates memory to hold Modbus ADU.

Parameters

pduSize	size of the PDU in bytes
context	context pointer passed on to the allocator

Returns: MODBUS_OK on success; MODBUS_ERROR_ALLOC on allocation failure

If called with pduSize == 0, the buffer is freed. Otherwise a buffer for (pduSize + buffer->padding) bytes is allocated. This guarantees that the buffer is big enough to hold the entire ADU.

This function is responsible for managing data, pdu and length fields in the buffer struct. The pdu pointer is set up to point pduOffset bytes after the data pointer unless data is a null pointer.

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◆ modbusBufferDestroy()

void modbusBufferDestroy	(	ModbusBuffer *	buffer,
		void *	context
	)

Equivalent of modbusBufferFree() \copydetail modbusBufferFree()

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◆ modbusBufferFree()

void modbusBufferFree	(	ModbusBuffer *	buffer,
		void *	context
	)

Frees memory allocated inside the buffer.

Parameters

context context pointer passed on to the allocator

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◆ modbusBufferInit()

ModbusErrorInfo modbusBufferInit	(	ModbusBuffer *	buffer,
		ModbusAllocator	allocator
	)

Initializes a buffer for use.

Parameters

allocator Memory allocator to be used by the buffer

Returns: MODBUS_NO_ERROR() on success

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◆ modbusBufferModePDU()

static void modbusBufferModePDU ( ModbusBuffer * buffer )

inlinestatic

Prepares buffer to only store a Modbus PDU.

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◆ modbusBufferModeRTU()

static void modbusBufferModeRTU ( ModbusBuffer * buffer )

inlinestatic

Prepares buffer to store a Modbus RTU message.

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◆ modbusBufferModeTCP()

static void modbusBufferModeTCP ( ModbusBuffer * buffer )

inlinestatic

Prepares buffer to store a Modbus TCP message.

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◆ modbusCheckRangeU16()

static uint8_t modbusCheckRangeU16	(	uint16_t	index,
		uint16_t	count
	)

inlinestatic

Checks whether provided address range causes an uint16_t overflow.

Parameters

index	index of the first register in the range
count	number of registers in the range

Returns: true if the range causes an overflow

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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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◆ modbusDefaultAllocator()

ModbusError modbusDefaultAllocator	(	ModbusBuffer *	buffer,
		uint16_t	size,
		void *	context
	)

The default memory allocator based on realloc()

Parameters

buffer	a pointer to the buffer to be reallocated
size	new desired buffer size in bytes
context	user's context pointer

Returns: MODBUS_ERROR_ALLOC on allocation failure; MODBUS_OK on success

See also: allocators

◆ modbusGetErrorCode()

static ModbusError modbusGetErrorCode ( ModbusErrorInfo err )

inlinestatic

Returns ModbusError contained in ModbusErrorInfo.

Returns: MdobusError contained in ModbusErrorInfo

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◆ modbusGetErrorSource()

static uint8_t modbusGetErrorSource ( ModbusErrorInfo err )

inlinestatic

Returns uint8_t describing error source of ModbusErrorInfo.

Returns: error source

See also: MODBUS_ERROR_SOURCE_GENERAL; MODBUS_ERROR_SOURCE_REQUEST; MODBUS_ERROR_SOURCE_REQUEST

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◆ modbusGetGeneralError()

static ModbusError modbusGetGeneralError ( ModbusErrorInfo err )

inlinestatic

Returns general error from ModbusErrorInfo.

Returns: ModbusError if ModbusErrorInfo contains an error from MODBUS_ERROR_SOURCE_GENERAL; MODBUS_OK otherwise

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◆ modbusGetRequestError()

static ModbusError modbusGetRequestError ( ModbusErrorInfo err )

inlinestatic

Returns request error from ModbusErrorInfo.

Returns: ModbusError if ModbusErrorInfo contains an error from MODBUS_ERROR_SOURCE_REQUEST; MODBUS_OK otherwise

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◆ modbusGetResponseError()

static ModbusError modbusGetResponseError ( ModbusErrorInfo err )

inlinestatic

Returns response error from ModbusErrorInfo.

Returns: ModbusError if ModbusErrorInfo contains an error from MODBUS_ERROR_SOURCE_RESPONSE; MODBUS_OK otherwise

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◆ modbusIsOk()

static uint8_t modbusIsOk ( ModbusErrorInfo err )

inlinestatic

Checks if ModbusErrorInfo contains an error.

Returns: true if ModbusErrorInfo contains an error

See also: MODBUS_NO_ERROR()

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◆ modbusMaskRead()

static uint8_t modbusMaskRead	(	const uint8_t *	mask,
		uint16_t	n
	)

inlinestatic

Reads n-th bit from an array.

Parameters

mask	A pointer to the array
n	Number of the bit to be read

Returns: The bit value

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◆ modbusMaskWrite()

static void modbusMaskWrite	(	uint8_t *	mask,
		uint16_t	n,
		uint8_t	value
	)

inlinestatic

Writes n-th bit in an array.

Parameters

mask	A pointer to the array
n	Number of the bit to write
value	Bit value to be written

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◆ modbusPackRTU()

static ModbusError modbusPackRTU	(	uint8_t *	frame,
		uint16_t	length,
		uint8_t	address
	)

inlinestatic

Sets up address and CRC in a Modbus RTU frame.

Parameters

frame	Pointer to the frame data
length	Length of the frame (valid range: 4 - 256)
address	Address of the slave

Returns: MODBUS_OK on success; MODBUS_ERROR_LENGTH if the length of the frame is invalid

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◆ modbusPackTCP()

static ModbusError modbusPackTCP	(	uint8_t *	frame,
		uint16_t	length,
		uint16_t	transactionID,
		uint8_t	unitID
	)

inlinestatic

Sets up the MBAP header in a Modbus TCP frame.

Parameters

frame	Pointer to the frame data
length	Length of the frame (valid range: 8 - 260)
transactionID	TCP transaction ID
unitID	Slave unit ID

Returns: MODBUS_OK on success; MODBUS_ERROR_LENGTH if the length of the frame is invalid

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◆ modbusRBE()

static uint16_t modbusRBE ( const uint8_t * p )

inlinestatic

Safely reads a big-endian 16-bit word from provided pointer.

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◆ modbusRLE()

static uint16_t modbusRLE ( const uint8_t * p )

inlinestatic

Safely reads a little-endian 16-bit word from provided pointer.

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◆ modbusUnpackRTU()

static ModbusError modbusUnpackRTU	(	const uint8_t *	frame,
		uint16_t	length,
		uint8_t	checkCRC,
		const uint8_t **	pdu,
		uint16_t *	pduLength,
		uint8_t *	address
	)

inlinestatic

Unpacks data from a Modbus RTU frame and optionally checks CRC.

Parameters

frame	Pointer to the frame data
length	Length of the frame (valid range: 4 - 256)
checkCRC	Controls whether the CRC of the frame should be checked
pdu	Output: pointer to the PDU
pduLength	Output: length of the PDU
address	Output: Slave address

Returns: MODBUS_OK on success; MODBUS_ERROR_LENGTH if the length of the frame is invalid; MODBUS_ERROR_CRC if the CRC is incorrect

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◆ modbusUnpackTCP()

static ModbusError modbusUnpackTCP	(	const uint8_t *	frame,
		uint16_t	length,
		const uint8_t **	pdu,
		uint16_t *	pduLength,
		uint16_t *	transactionID,
		uint8_t *	unitID
	)

inlinestatic

Unpacks data from a Modbus TCP frame.

Parameters

frame	Pointer to the frame data
length	Length of the frame (valid range: 8 - 260)
pdu	Output: pointer to the PDU
pduLength	Output: length of the PDU
transactionID	Output: TCP transaction ID
unitID	Output: Slave unit ID

Returns: MODBUS_OK on success; MODBUS_ERROR_LENGTH if the length of the frame is invalid or if the length declared inside the frame does not match the actual frame length; MODBUS_ERROR_BAD_PROTOCOL if the protocol ID declared in frame is not 0

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◆ modbusWBE()

static uint16_t modbusWBE	(	uint8_t *	p,
		uint16_t	val
	)

inlinestatic

Safely writes a big-endian 16-bit word to provided pointer.

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◆ modbusWLE()

static uint16_t modbusWLE	(	uint8_t *	p,
		uint16_t	val
	)

inlinestatic

Safely writes a little-endian 16-bit word to provided pointer.

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Data Structures

Macros

Typedefs

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ LIGHTMODBUS_ALWAYS_INLINE

◆ LIGHTMODBUS_RET_ERROR

◆ LIGHTMODBUS_WARN_UNUSED

◆ MODBUS_ERROR_SOURCE_GENERAL

◆ MODBUS_ERROR_SOURCE_REQUEST

◆ MODBUS_ERROR_SOURCE_RESERVED

◆ MODBUS_ERROR_SOURCE_RESPONSE

◆ MODBUS_GENERAL_ERROR

◆ MODBUS_MAKE_ERROR

◆ MODBUS_NO_ERROR

◆ MODBUS_PDU_MAX

◆ MODBUS_PDU_MIN

◆ MODBUS_REQUEST_ERROR

◆ MODBUS_RESPONSE_ERROR

◆ MODBUS_RTU_ADU_MAX

◆ MODBUS_RTU_ADU_MIN

◆ MODBUS_RTU_ADU_PADDING

◆ MODBUS_RTU_PDU_OFFSET

◆ MODBUS_TCP_ADU_MAX

◆ MODBUS_TCP_ADU_MIN

◆ MODBUS_TCP_ADU_PADDING

◆ MODBUS_TCP_PDU_OFFSET

Typedef Documentation

◆ ModbusAllocator

◆ ModbusBuffer

◆ ModbusDataType

◆ ModbusError

◆ ModbusErrorInfo

◆ ModbusExceptionCode

Enumeration Type Documentation

◆ ModbusDataType

◆ ModbusError

◆ ModbusExceptionCode

Function Documentation

◆ modbusBitsToBytes()

◆ modbusBufferAllocateADU()

◆ modbusBufferDestroy()

◆ modbusBufferFree()

◆ modbusBufferInit()

◆ modbusBufferModePDU()

◆ modbusBufferModeRTU()

◆ modbusBufferModeTCP()

◆ modbusCheckRangeU16()

◆ modbusCRC()

◆ modbusDefaultAllocator()

◆ modbusGetErrorCode()

◆ modbusGetErrorSource()

◆ modbusGetGeneralError()

◆ modbusGetRequestError()

◆ modbusGetResponseError()

◆ modbusIsOk()

◆ modbusMaskRead()

◆ modbusMaskWrite()

◆ modbusPackRTU()

◆ modbusPackTCP()

◆ modbusRBE()

◆ modbusRLE()

◆ modbusUnpackRTU()

◆ modbusUnpackTCP()

◆ modbusWBE()

◆ modbusWLE()