serial_rs232_buffer_ring

Serial/RS232 Buffer Ring

Explanation:

This program demonstrates how to create a serial input buffer ring.

The program receives a character into the buffer and sends back. Try sending large volumes of characters…​..

This program program uses an interrupt event to capture the incoming byte value and place in the buffer ring. When a byte is received the buffer ring is incremented to ensuer the next byte is handled correctly.

Testing bkbhit will set to True when a byte has been received. Reading the function bgetc will return the last byte received.

Demonstration program:

This demonstration program will support up to 256 bytes. For a larger buffer change the variables to words.

    #chip 16F1937


    ' Add PPS if appropiate for your chip
    ' [change to your config] This is the config for a serial terminal

    ' assumes USART1
    ' turn on the RS232 and terminal port.
    ' Define the USART settings
    #DEFINE USART_BAUD_RATE 9600

    'This assumes you are using an ANSI compatible terminal.  Use PUTTY.EXE it is very easy to use.

    '   Main program

    'Wait for terminal to settle
    wait 3 s

    'Create the supporting variables
    Dim next_in As Byte
    Dim next_out As Byte
    Dim syncbyte As Byte
    Dim temppnt As Byte

    ' Constants etc required for Buffer Ring
    #DEFINE BUFFER_SIZE 8
    #DEFINE bkbhit (next_in <> next_out)

    'Define the Buffer
    Dim buffer( BUFFER_SIZE - 1 ) 'we will use element 0 in the array as part of out buffer

    'Call init the buffer
    InitBufferRing

    HSerSend 10
    HSerSend 13
    HSerSend 10
    HSerSend 13
    HSerPrint "Started: Serial between two devices"
    HSerSend 10
    HSerSend 13


    'Get character(s) and send back
    Do

        ' Do we have data in the buffer?
        if bkbhit then

            'Send the next character in the buffer, exposed via the function `bgetc` back the terminal
            HSerSend bgetc

        end if

    Loop

    'Supporting subroutines

    Sub readUSART

        buffer(next_in) = HSerReceive
        temppnt = next_in
        next_in = ( next_in + 1 ) % BUFFER_SIZE
        If ( next_in = next_out ) Then  ' buffer is full!!
            next_in = temppnt
        End If

    End Sub

    Function bgetc
        Dim local_next_out as Byte    'maintain a local copy of the next_out variable to ensure it does not change when an Interrupt happens
        local_next_out = next_out
        bgetc = buffer(local_next_out)
        local_next_out=(local_next_out+1) % BUFFER_SIZE
        INTOFF
        next_out = local_next_out
        INTON
    End Function




    Sub InitBufferRing

        'Set the buffer to the first address
        next_in = 0
        next_out = 0
        'Interrupt Handler - some have RCIE and some have U1RXIE, so handle
        #IFDEF BIT( RCIE )
            On Interrupt UsartRX1Ready Call readUSART
        #ENDIF
        #IFDEF BIT( U1RXIE )
            On Interrupt UART1ReceiveInterrupt Call readUSART
        #ENDIF
        #IFDEF AVR
            On Interrupt UsartRX1Ready Call readUSART
        #ENDIF

    End Sub