Interrupt driven Buffered Serial Input

[johnmiller]

Well my program needs to read the data from a serial connection and than it should save that data into a string. The only problem that I have is that if the date comes too quickly the PIC just discards that data. Any ideea why is that?

[Darrel Taylor]

Possibly because you are sending anything received back out at the same speed within the interrupt handler.

You should get in and out of the handler as quick as possible.
Then let the mainloop empty the buffer when it has time.
Preferably at a higher speed.

Also, T0CON is different than T1CON.
TMR0ON is bit 7, and bit 0 is part of the prescaler setting.
<br>

[johnmiller]

I tried this code:

ReadSerial:
   DataRec var byte[5] : DataRec = 0
   KP var byte : KP = 0
   
   While CounterA <= 70
      IF index_in > (buffer_size-1) Then index_in = 0	'Reset pointer if outside of buffer
	  HSerin [buffer[index_in]]		   ' Read USART and store character to next empty location

	  if buffer(index_in) = $20 then 
         index_in = 0
         for CounterB=0 to buffer_size
             buffer(CounterB) = 0
             next CounterB
         KP = 1
      ENDIF

      if ((KP = 1) AND (index_in=4)) THEN
         SerData(CounterA)=buffer(4)
         CounterA = CounterA + 1
         KP = 1
      ENDIF
      index_in = index_in + 1
   WEND

and it still doesn't work any ideea why.

PS: Is it better than the old one?

[skimask]

@ DEVICE PIC16F628A , HS_OSC , WDT_OFF , PWRT_ON , MCLR_ON , BOD_ON , LVP_OFF , PROTECT_OFF
'HS 20mhz external, watchdog off, powerup timer on, mclr external, brown out detect on, low volt program off , code protect off

resetplaceholder: 'wordpad, arial black, size 8, reg, 1600x1200 screen, 16f628A code
DEFINE	OSC	20	'20mhz

serdata var byte : serialbuffer var byte[255] : bufferpointer var byte
bufferdata var byte : temp var byte

startupholder:	goto skipsubs	'skip over all the commonly used subroutines

ON INTERRUPT GOTO INTHANDLER
DISABLE INTERRUPT
INTHANDLER:	if pir1.5 = 1 then	'if serial data rx'd
			serdata = rcreg		'save serial port data right away
			pir1.5 = 0		'reset the RX flag
			if ( rcsta.1 = 1 ) or ( rcsta.2 = 1 ) then	'check for err, if frame/overrun error,
				rcsta.4 = 0 : rcsta.4 = 1 : serdata = rcreg : serdata = 0
			else
				if bufferpointer = 255 then goto intfinish	'buffer is full
				serialbuffer[bufferpointer] = serdata
 : bufferpointer = bufferpointer + 1	'save data in buffer, bump pointer
				goto INTHANDLER	're-check serial port just in case another character came in while saving data
                                                        '...not likely
			endif
		endif

intfinish:	RESUME
ENABLE INTERRUPT

getcharacterfrombuffer:
		if bufferpointer = 0 then return	'no data in buffer in the first place!
		buffereddata = serialbuffer[0]	'get oldest data from buffer
		for temp = 0 to 254 : serialbuffer[temp] = serialbuffer[temp+1] : next temp	'shift data down one byte
		serialbuffer[255]=0	'set last byte in buffer to zero since it's meaningless
		bufferpointer = bufferpointer - 1	'one less byte in buffer
		return

skipsubs:	option_reg=8 : pie1=32 : trisa=0 : porta=0 : trisb=$ef : portb=16 : t1con=0 : t2con=0
		cmcon=7 : ccp1con=0 : vrcon=0 : txsta=0 : rcsta=$90 : pir1.5=0 : spbrg=33 : intcon=$e0	'9600 baud
		for temp = 0 to 255 : serialbuffer[temp] = 0 : next temp

mainloop:	goto mainloop	'do it all over again

END

I modified one of my old programs. This works for me, always has.
I've left the character handling and the modifications of the program to you to make work for your PIC.

[johnmiller]

I tried your code, and now I tried the one above and still does not work

ReadSerial:
   DataRec var byte[5] : DataRec = 0
   
   While CounterA <= 55
        HSERIN [serdata2]        'save serial port data right away
        if serdata2 = $13 THEN
           i = 0
           KP = 1
        ENDIF
        if KP = 1 then
           IF i=5 THEN
              SerData(CounterA) = serdata2
              CounterA = CounterA + 1
              KP = 0
           endif
           i = i + 1
        endif
   wend

   FOR COUNTERB=42 to COUNTERA
        SEROUT2 SerWRT,16416,[hex2 SerDATA(COUNTERB), 10, 13]
        NEXT COUNTERB
   Goto ReadReadyLoop

I tried this one as well and it doesn't work either:

    SERIN2 [WAIT($20), SKIP 4, serdata2]

PS: it doesn't work it's like the pic is not reading the data fast enough. It is supposed to read the data from a keyboard that than sends data over a serial link at 19200 (not inverted).

All the above codes work if I press a key once per second or so, but they don't work any faster. Anybody can tell me why

[skimask]

I think I can reasonably assume that what you posted isn't all of your code that you are trying to make work.
And if it is...well, where's the beef?
Post the whole thing if you want any useful help...

[johnmiller]

Well this is the only part where I have problems and I don't think pasting 80 pages will do any good
I really don't understand what's wrong with my code