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Serial.md

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Serial Communication Components

All serial components extend CyclicComponent and depend on an I_SerialLineControl instance that owns the hardware RX/TX buffers. Two line control implementations are provided: SerialLineControl_ADS (ADS-routed) and SerialLineControl_Terminal (direct hardware).

SerialByteConnection

Sends and receives single bytes over a serial line.

Extends: CyclicComponent
Implements: I_SerialByteConnection

Interface

Member Type Description
FB_Init(Name, SerialLineController) Constructor Binds to an I_SerialLineControl
ByteData BYTE (Get) Most recently received byte
ByteDataRecieved BOOL (Get) TRUE (once) when a new byte has arrived; auto-clears on read
SendAByte(DataToSend) Method Queues a byte for transmission
Reset() Method Clears RX buffer and resets counters
CyclicLogic() Method Must be called each scan

Example

VAR
    LineCtrl : SerialLineControl_ADS('COM1 ADS');
    Conn     : SerialByteConnection('ByteConn', LineCtrl);
    RxByte   : BYTE;
END_VAR

LineCtrl.CyclicLogic();
Conn.CyclicLogic();

IF Conn.ByteDataRecieved THEN
    RxByte := Conn.ByteData;
END_IF

Conn.SendAByte(16#06);  // Send ACK

SerialStringConnection

Sends and receives null-terminated strings over a serial line. Supports configurable prefix/suffix delimiters for framing.

Extends: CyclicComponent
Implements: I_SerialStringConnection

Interface

Member Type Description
FB_Init(Name, SerialLineController) Constructor Binds to an I_SerialLineControl
StringData T_MaxString (Get) Most recently received string
StringRecieved BOOL (Get) TRUE (once) when a complete string has arrived; auto-clears on read
SendAString(DataToSend) Method Queues a string for transmission
SetSerialConfiguration(Prefix, Suffix) Method Sets the start/end delimiters for string framing
Reset() Method Clears RX buffer and resets state
CyclicLogic() Method Must be called each scan

Example

VAR
    LineCtrl : SerialLineControl_ADS('COM2 ADS');
    Conn     : SerialStringConnection('StringConn', LineCtrl);
    Response : T_MaxString;
END_VAR

// Frame strings with STX/ETX
Conn.SetSerialConfiguration(Prefix := '$02', Suffix := '$03');

LineCtrl.CyclicLogic();
Conn.CyclicLogic();

IF Conn.StringRecieved THEN
    Response := Conn.StringData;
    // Process response...
END_IF

Conn.SendAString('READ?');

SerialLineControl_ADS

Routes serial communication through ADS to a TwinCAT serial port server. Use when the COM port is not on the local runtime.

Implements: I_SerialLineControl

Interface

Member Type Description
FB_Init(Name) Constructor Standard name
rxBuffer RX buffer reference Consumed by SerialByteConnection / SerialStringConnection
txBuffer TX buffer reference Written to by send methods
CyclicLogic() Method Must be called each scan

SerialLineControl_Terminal

Direct serial communication using Beckhoff serial terminal hardware (e.g., EL6001/EL6002). Use when the COM port is accessed via EtherCAT terminal I/O mapping.

Implements: I_SerialLineControl

Same interface as SerialLineControl_ADS.