AsciiRead (FB)

FUNCTION_BLOCK AsciiRead EXTENDS AC500_StateMachine.AbbLConC3

Function block to read incoming serial messages as ASCII code and validate them according to defined telegram ending parameter.

Once the corresponding message is received, the Ready output is set to TRUE for one cycle. The output Message will display the actual message without the ending and the output Length will give corresponding length without the ending. Per default the maximum size of Message is set to 255 characters. To read messages beyond 255 characters, the library parameter CharLength must be increased.

Hint

The max size of Message is 255 by default and can be increased with the CharLength parameter.

An internal buffer is used to store the read data. The buffer is set to 5000 caracters by default and can be modified according to the needs by changing the library parameter InternalBufferSize. If the buffer exceeds, because the ending telegram is never reached, the function block will return an error ERR_BUFFER_OVERFLOW.

Warning

The internal buffer of the function block is cleaned once Enable is set to FALSE.

Resetting the function block by setting Enable from TRUE -> FALSE will close the COM port if AsciiWrite is not in use. Elswise, if AsciiWrite is used in parallel, the COM port remains open to fulfill the write job and is then automatically closed by the AsciiWrite.

Closing the COM port and therefore resetting the AsciiRead requires more cycles to be performed reliable. Therefore, the outputs Busy and Error must be monitored to check whether resetting has been finished or not.

Hint

When the COM port is closed, the Linux buffer is cleaned up and already received information are lost.

Telegram ending

Telegram ending selection	Telegram ending size	Telegram ending value	Description
None			No telegram ending identifier selected. The character received since last call are provided. The maximum number of characters is limited to the parameter setting of the Ascii library and can be modified by changing the size for CharLength.
Character	Number of ending characters 1 or 2	Character values, e.g. 16#0D0A <CR><LF>	According to the set value, it is checked for 1 or 2 ending characters. The ending character(s) is (are) not passed, i.e. they are not contained in the `Message`output
Telegram length		Number of characters > 0 and <= CharLength (Param List)	Telegram received is reported once the number of characters defined in “Value” is received.
Duration		Time in [ms]	Telegram received is reported once the time set for “Value” is elapsed. The time starts with the first FALSE -> TRUE at input Enable and will reset after successfull receive of the data.
Telegram timeout		Time in [ms]	Telegram received is reported once the pause between two telegrams is greater than the time set in “Value”. The time starts with the first received bytes and will restart every time new bytes are received. If the time exceeds, the message is returned.

InOut:

Scope	Name	Type	Initial	Comment	Inherited from
Input	Enable	BOOL	FALSE	A rising edge (Enable = TRUE) starts the operation, the output Busy goes to TRUE. All other inputs are read and considered continuously. Execution will continue forever until a falling edge (Enable = FALSE) aborts the operation. During Aborting the Busy is still TRUE. Afterward all outputs are reset.	AbbLConC3
Output	Busy	BOOL	FALSE	Operation is running (while output Error is FALSE)	AbbLConC3
	Error	BOOL	FALSE	Operation is stopped with error (while output Busy is FALSE). This output is TRUE for at least one cycle or until Enable is set to FALSE. The output ErrorID gives more details about the error.	AbbLConC3
Input	Com	STRING	‘COM_1’	Node name of the serial interface
	TelegramEnding	TELEGRAM_ENDING		Telegram ending parameter
Output	ErrorId	ERROR_ID	ERROR_ID.NO_ERROR	ErrorId <> NO_ERROR if output Error = TRUE
	AddErrNo	DWORD		Additional error number to indicates errors coming from underlying libraries. Please check AC500_Com.COM.ERROR enumeration for references
	Ready	BOOL		Rising flag that indicates a new message is present at Message output. Ready will be TRUE for only one cycle
	Message	STRING(Param.CharLength)		Received message according to definition of telegram ending
	Length	UDINT		Length of the actual message