FB_CSVMemBufferReader

This function block can be used to decompose/interpret data sets stored in an external buffer into individual data fields. The buffer data could first be read from a file with the aid of the function blocks for file access, for example. The function block reads the first or the next data field and returns its value either as a string at the getValue output or as an address/byte value at the pValue/cbValue output.

The data in the buffer must have a certain format to ensure that the function block can interpreted them correctly. CRLF (CR=Carriage Return, LF=Line Feed) must be used as a data set separator. The last data set must end with a CRLF. Individual data fields must be separated with the data field separator. The default data field separator is a semicolon. The separator can be configured from semicolon to comma via the global PLC variable DEFAULT_CSV_FIELD_SEP.

VAR_INPUT

VAR_INPUT
    eCmd     : E_EnumCmdType := eEnumCmd_First;
    pBuffer  : POINTER TO BYTE;
    cbBuffer : UDINT;
END_VAR

eCmd: Control parameter for the buffer component (type: E_EnumCmdType). eEnumCmd_First reads the first data field, eEnumCmd_Next reads the next data field. No other parameter values are used.

pBuffer: Address (pointer) for the source buffer variable. The address can be determined with the ADR operator. This buffer contains the data set/data field data to be read.

cbBuffer: The byte size of the data to be interpreted in the source buffer (data set/data field data). The buffer size may be much larger than the amount of data to be interpreted. Please enter the actual length of the data to be interpreted.

VAR_OUTPUT

VAR_OUTPUT
    bOk      : BOOL;
    getValue : T_MaxString := '';
    pValue   : POINTER TO BYTE := 0;
    cbValue  : UDINT := 0;
    bCRLF    : BOOL := FALSE;
    cbRead   : UDINT := 0;
END_VAR

bOk: TRUE = Success, FALSE = Faulty data/faulty input parameters, or the end of the data was reached and no further data field could be read.

getValue: The last read data field as string (type: T_MaxString). For data fields without control characters and binary data, this output returns the complete data field as a null-terminated string. However, data fields with control characters or binary data can return an incomplete string at this output. In this case the outputs pValue/cbValue are used to access the last read data field.

pValue: Address (pointer) to the first data byte in the data field. Please note that empty void data fields are not terminated with null (as is usual for a PLC string) and therefore have no data. In this case the address is null.

cbValue: Data field length in bytes. Please note that empty void data fields are not terminated with null (as is usual for a PLC string) and therefore have no data. The length is also null in this case. The maximum size can be specified with the global parameter cMaxCSVFieldValueSize.

bCRLF: This output is set if the end of the data set was reached during the last read command. The last read data field belongs to the previous data set. The next data field belongs to a new data set.

cbRead: Number of successfully read/interpreted data bytes. This number may be greater than the data field length at the cbValue output. The length at the cbRead output includes the interpreted data field/data set separators.

Example:

See: Example: Writing/reading of a CSV file.

Requirements

Development environment	Target platform	PLC libraries to be integrated (category group)
TwinCAT v3.1.0	PC or CX (x86, x64, ARM)	Tc2_Utilities (System)