Modbus data types

FairCom Edge's `"modbusDataType"` action returns the Modbus data type which defines how to convert binary data types into JSON types

Abstract

The Modbus data types are the values used in the modbusDataType property which defines how to convert Modbus binary data types into JSON types

The Modbus data types are the values used in the "modbusDataType" property which defines how to convert Modbus binary data types into JSON types.

Integer data types

Modbus integer types can be converted into JSON numbers. At the binary level, a JSON number is an array containing one or more of the ASCII characters (-0123456789.), including the period.

Table 1. Integer data types

`"modbusDataType"`	Description	Data type	Bit size	Signed/unsigned	Endian	Swap bytes	Device byte order	Converted byte order
int8Signed		integer	8	signed
int8Unsigned		integer	8	unsigned
int16Signed	Int16 signed big endian	integer	16	signed	big		AB	AB
int16Unsigned	Int16 unsigned big endian	integer	16	unsigned	big		AB	AB
int16SignedSwap	Int16 signed little endian	integer	16	signed	little		BA	AB
int16UnsignedSwap	Int16 unsigned little endian	integer	16	unsigened	little		BA	AB
int32SignedABCD	Int32 signed big endian	integer	32	signed	big		ABCD	ABCD
int32UnsignedABCD	Int32 unsigned big endian	integer	32	unsigned	big		ABCD	ABCD
int32SignedDCBA	Int32 signed little endian	integer	32	signed	little		DCBA	ABCD
int32UnsignedDCBA	Int32 unsigned little endian	integer	32	unsigned	little		DCBA	ABCD
int32SignedBADC	Int32 signed big endian byte swapped	integer	32	signed	big	swap	BADC	ABCD
int32UnsignedBADC	Int32 unsigned big endian byte swapped	integer	32	unsigned	big	swap	BADC	ABCD
int32SignedCDAB	Int32 signed little endian byte swapped	integer	32	signed	little	swap	CDAB	ABCD
int32UnsignedCDAB	Int32 unsigned little endian byte swapped	integer	32	unsigned	little	swap	CDAB	ABCD
int64Signed	Int64 signed big endian	integer	64	signed	big		ABCDEFGH	ABCDEFGH
int64Unsigned	Int64 unsigned big endian	integer	64	unsigned	big		ABCDEFGH	ABCDEFGH
int64SignedLittleEndian	Int64 signed little endian	integer	64	signed	little		HGFEDCBA	ABCDEFGH
int64UnsignedLittleEndian	Int64 unsigned little endian	integer	64	unsigned	little		HGFEDCBA	ABCDEFGH

IEEE float data types

Modbus float types can be converted to a JSON number.

Table 2. IEEE float date types

Name for the binary data type of the source	Description	Data type	Bit size	Endian	Swap bytes	Device byte order	Converted byte order
ieeeFloat32	IEEE 32-bit float little endian	IEEE float	32	little		DCBA	ABCD
ieeeFloat32Swap	IEEE 32-bit float little endian byte swapped	IEEE float	32	little	swap	BADC	ABCD
ieeeFloat64	IEEE 64-bit float little endian	IEEE float	64	little		HGFEDCBA	ABCDEFGH
ieeeFloat64Swap	IEEE 64-bit float big endian byte swapped	IEEE float	64	big	swap	BADCFEHG	ABCDEFGH

Boolean data types

Modbus Boolean types can be converted to a JSON true or false.

Table 3. Boolean date types

Name for the binary data type of the source	Description	Data type	Bit size	Signed/unsigned
boolean	converts any size of register to `false` when all bits are zero; otherwise, `true`	Boolean	any	zero = false
booleanZeroTrue	converts any size of register to `true` when all bits are zero; otherwise, `false`	Boolean	any	zero = true

Date-time data types

Modbus date-time data type parts can be combined from different registers to create a JSON string containing and ISO 8601 time (yyyy-mm-ddThh:mm:ss.nnn).

Viable date-time formats:

Date time with milliseconds (yyyy-mm-ddThh:mm:ss.nnn)
Date time without milliseconds (yyyy-mm-ddThh:mm:ss)
Date time without seconds (yyyy-mm-ddThh:mm)
Date time without minutes (yyyy-mm-ddThh:mm)
Date without time (yyyy-mm-dd)
Date with only year and month (yyyy-mm)
Date with only year (yyyy)

Table 4. Date-time data types

Name of the binary data type of the source	Description	Data type	Bit size
datetimeSchneiderUp	Date time used by Schneider Electric with different formats for 16-bit and 32-bit registers	ULP DateTime	16 or 32
utc	ASCII string representing a UTC time - works in JSON without conversion	ASCII string	8
year	separate register combined with other registers to create a datetime	unsigned integer	any
month	separate register combined with other registers to create a datetime	unsigned integer	any
day	separate register combined with other registers to create a datetime	unsigned integer	any
hours	separate register combined with other registers to create a datetime	unsigned integer	any
minutes	separate register combined with other registers to create a datetime	unsigned integer	any
seconds	separate register combined with other registers to create a datetime	unsigned integer	any
milliseconds	separate register combined with other registers to create a datetime	unsigned integer	any

String data types

The Modbus string types can be converted to JSON strings that consist of UTF-8 characters.

Table 5. String data types

Name of data type in the binary source	Description	Data type	Bit size	Swap bytes	Device byte order	Converted byte order
ascii8	8-bit ASCII Latin character set to UTF-8	ASCII Latin string	8
ascii16AB	16-bit bit endian ASCII Latin character set to UTF-8	ASCII Latin string	16		AB	AB
ascii16BA	16-bit little endian ASCII Latin character set to UTF-8	ASCII Latin string	16	swap	BA	AB
ascii32ABCD	32-bit big endian ASCII Latin character set to UTF-8	ASCII Latin string	32		ABCD	ABCD
ascii32DCBA	32-bit little endian ASCII Latin character set to UTF-8	ASCII Latin string	32		DCBA	ABCD
ascii32BADC	32-bit big endian byte swapped ASCII Latin character set to UTF-8	ASCII Latin string	32	swap	BADC	ABCD
ascii32CDAB	32-bit little endian byte swapped ASCII Latin character set to UTF-8	ASCII Latin string	32	swap	CDAB	ABCD
utf8	No conversion	UTF-8 string	8
ucs2AB	16-bit big endian unicode UCS-2 to UTF-8	UTF-2 string	16		AB	AB
ucs2BA	16-bit little endian unicode UCS-2 to UTF-8	UTF-2 string	16	swap	BA	AB