FB_JsonReadWriteDataType

In order to use UTF-8 characters, e.g. in the automatic generation of metadata via the function block FB_JsonReadWriteDataType, the check box for the support of UTF-8 in the symbolism must be activated in the TwinCAT project. To do this, double-click on SYSTEM in the project tree, open the Settings tab and activate the corresponding check box.

	Strings in UTF-8 format The variables of type STRING used here are based on the UTF-8 format. This STRING formatting is common for MQTT communication as well as for JSON documents. In order to be able to receive special characters and texts from a wide range of languages, the character set in the Tc3_IotBase and Tc3_JsonXml libraries is not limited to the typical character set of the data type STRING. Instead, the Unicode character set in UTF-8 format is used in conjunction with the data type STRING. If the ASCII character set is used, there is no difference between the typical formatting of a STRING and the UTF-8 formatting of a STRING. Further information on the UTF-8 STRING format and available display and conversion options can be found in the documentation for the Tc2_Utilities PLC library.

Outputs

Name	Type
initStatus	HRESULT

Methods

Name	Description
FB_JsonReadWriteDataType	Metadata can be added via PLC attributes to the JSON representation of a PLC data structure on an FB_JsonSaxWriter object.
AddJsonKeyValueFromSymbol	Creates the JSON representation of a PLC data structure on an FB_JsonSaxWriter object.
AddJsonValueFromSymbol	Creates the JSON representation of a PLC data structure on an FB_JsonSaxWriter object.
CopyJsonStringFromSymbol	Creates the JSON representation of a symbol and copies it to a variable of data type STRING.
CopyJsonStringFromSymbolProperties	Creates a corresponding JSON representation of PLC attributes on a symbol.
CopySymbolNameByAddress	Returns the complete (ADS) symbol name of a transferred symbol.
GetDataTypeNameByAddress	Returns the data type name of a transferred symbol.
GetJsonFromSymbol	Creates the corresponding JSON representation of a symbol.
GetJsonStringFromSymbol	Creates the corresponding JSON representation of a symbol.
GetJsonStringFromSymbolProperties	Creates a corresponding JSON representation of PLC attributes on a symbol.
GetSizeJsonStringFromSymbol	Reads the size of the JSON representation of a symbol.
GetSizeJsonStringFromSymbolProperties	Reads the size of the JSON representation of PLC attributes on a symbol.
GetSymbolNameByAddress	Returns the complete (ADS) symbol name of a transferred symbol.
SetSymbolFromJson	Extracts a string containing a valid JSON message.

Requirements

TwinCAT version	Hardware	Libraries to be integrated
TwinCAT 3.1, Build 4022	x86, x64, ARM	Tc3_JsonXml

Further Information