This module provides interrupt driven RS232 buffering.

• Start
• Halt
• DataAvailable
• ReadByte
• ReadString
• Reset
• OnData
• OnOverrun
• Program Example

Start

Start buffering incoming data.

Halt

 Sub Halt()

Stop buffering incoming data.

DataAvailable

 Function DataAvailable() As Boolean

Checks to see if there is any data in the input buffer. Returns true if data present, false otherwise.

ReadByte

 Function ReadByte() As Byte

Read a single byte from the input buffer. A call to DataAvailable() should be made before making this call to ensure that data is present in the input buffer.

ReadString

 Function ReadString(ByRef text As String) As Byte

• text - String variable to receive the data.

Read a string from the buffer. The function returns the number of bytes read. The routine expects the string to have a null terminator.

Reset

 Sub Reset()

Reset the module. A call to Halt() should be made before making a call to this routine.

OnData

 Event OnData(ByRef data As Byte, ByRef accept As Boolean)

• data - Input byte that is about to be placed into the buffer.
• accept - This flag should be set to false to indicate that the data byte should not be added to the buffer. By default it is true.

An event which enables incoming data to be changed or to prevent incoming data from being added to the buffer. See the program at the bottom of the page for a working example. This event is fired from the main interrupt handling routine. It is advised that the handler returns as soon as possible and that no calls are made to any other function or subroutine when the handler is executing.

OnOverrun

 Event OnOverrun()

An event which is fired when the input buffer becomes full. This event is fired from the main interrupt handling routine. It is advised that the handler returns as soon as possible and that no calls are made to any other function or subroutine when the handler is executing.

Example

' imports...
imports UartBuffer
imports Uart

' this event handler is triggered when data is received - it gives
' the program the opportunity to accept or reject the incoming byte
' or modify the data in some way - this example changes all space
' characters to underscore...
Sub OnData(ByRef Data As Byte, ByRef Accept As Boolean) Handles RX.OnData
   Dim DataIn As Byte = Data
   If DataIn = CByte(" ") Then
      Data = "_"
   End If
End Sub

' this event is fired if the RX buffer overruns...
Sub OnOverrun () Handles RX.OnOverrun
   High(PORTB.15)
End Sub

' main program...
Sub Main()
   UART.SetBaudrate(UART.Baudrate.Is38400) ' set baudrate
   RX.Start()                              ' start buffering data

   ' loop forever to prevent program
   ' from terminating...
   While True
      If RX.DataAvailable() Then      ' if data is available
         Console.Write(RX.ReadByte()) ' then echo back
      End If
   End While
End Sub