Hserin with Instant Interrupts.

[MichelJasmin]

This is what I do with DT_Interrupts on a serial stream of 115kBps on a PIC18F25k22 @44.2368MHz.

"Buffer" is a circular buffer of 256 bytes. When BufferReady = 1, I use another pointer (ParsePtr) to parse the data.

'----[interrupts Handlers]-------------------------------------------------------
RX_IntHandler:
    IF (RCSTA1.2 = 1) THEN
        ' A framing error occurred.
        ' Read RCREG to clear the error but don't use the data.
        CharBuff = RCREG1

    ELSE
       ' No framing error occurred. Get caracter.
       CharBuff = RCREG1

        If CharBuff <= 10 Then
            Buffer(BuffPtr) = 0
            BuffPtr = BuffPtr + 1
            BufferReady = 1

        Else
            If CharBuff >= 32 Then
                Buffer(BuffPtr) = CharBuff
                BuffPtr = BuffPtr + 1
            ENDIF
        ENDIF
    ENDIF

    @ INT_RETURN

[HenrikOlsson]

Hi Andy,

Looking at the original code I think at least one problem is the presense of the PAUSE in main routine.

When using ON INTERRUPT the interrupt flag is checked in between each PBP statement. If characters start to come in while the PIC is exectuing a PAUSE 150 satements you're going to flood the USART buffer since the interrupt isn't serviced untill after the PAUSE 150 finishes.

Same thing with the LCDOUT and PAUSE statements and in the master. They takes some time to execute and the interrupt flag is checked ONLY in between each statement so if the slave starts responding while the master is in the middle of printing to the LCD or executing a PAUSE the slave is going to flood the buffer of the master.

That's the downside of ON INTERRUPT.

/Henrik.