Hey,

Thanks a lot for your while(RCIF) tip. I'm already busy starting up my
vmware session to make the change and test it. Exactly the type of
things I was hoping for.

Re. your FIFO tip? How do you implement this fifo?

Quintin Beukes



On Fri, Oct 9, 2009 at 5:17 PM, Harold Hallikainen
<harold@hallikainen.org> wrote:
> You don't specify which PIC you're using, but the UARTs tend to be
> similar. From http://ww1.microchip.com/downloads/en/DeviceDoc/41350C.pdf,
> we find:
>
> 16.1.2.4 Receive Interrupts
> The RCIF interrupt flag bit of the PIR1 register is set
> whenever the EUSART receiver is enabled and there is
> an unread character in the receive FIFO. The RCIF
> interrupt flag bit is read-only, it cannot be set or cleared
> by software.
>
> So, the RCIF=3D0 does nothing since the bit is read only. As others have
> pointed out, there is a small FIFO in the UART. Because of this, I'd
> change the if(RCIF) to while(RCIF). This will loop the routine that pulls
> data from the UART until it is empty.
>
> Finally, I like putting stuff from the UART ISR into a FIFO instead of a
> linear buffer. In your non-interrupt code, you can pull data from the FIFO
> and put it in the linear buffer for command interpretation at your
> leisure. Putting data into the command interpreter buffer in the interrupt
> requires the mainline code to act quickly on finding the end of command
> before new data comes in and overwrites the command. Or, the command
> interpreter could be in the ISR, but I like to keep them small and fast.
> Of course, if the other end does not send a new command before getting a
> response from this end, dropping directly into the linear buffer would
> work fine.
>
> In a recent project (movie theater closed captioning receiver), I have
> packets of data coming in at 10kbps. It takes a variable amount of time to
> deal with the data (most of the time just sticking it in a linear array,
> but at the end of a packet doing a CRC check and then acting on it if
> good), so the amount of data in the FIFO between the ISR and the mainline
> code grows and shrinks as required so nothing gets lost.
>
> Good luck!
>
> Harold
>
>
>
>
>>
>> =A0 =A0 if (RCIF)
>>
>> =A0 =A0 {
>>
>> =A0 =A0 =A0 =A0 char c =3D RCREG;
>>
>>
>>
>> =A0 =A0 =A0 =A0 SerialRecordCharacter(c);
>>
>>
>>
>> =A0 =A0 =A0 =A0 RCIF =3D 0;
>>
>> =A0 =A0 }
>>
>
>
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