Interrupt driven Buffered Serial Input

[johnmiller]

Hi, I'm going mad for the past few days here since my interrupts are not working. I am trying to make a interrupt driven buffered serial input but without success since my program doesn't do anything when it should deal with the interrupts (it just stays on that "While CounterA <= 70 : WEND" forever) (nothing is printed out when I send something to it's serial port). Here is my code (part of it at least that deals with the serial part)

    DEFINE OSC 20
    
    DEFINE HSER_TXSTA 24h
    DEFINE HSER_RCSTA 90h
    DEFINE HSER_BAUD 19200
    DEFINE HSER_SPBRG 64 ' 19200 Bauds
    DEFINE HSER_CLROERR 1

    RCIF	VAR	PIR1.5		' Alias RCIF (USART Receive Interrupt Flag)
    OERR	VAR	RCSTA.1		' Alias OERR (USART Overrun Error Flag)
    CREN	VAR	RCSTA.4		' Alias CREN (USART Continuous Receive Enable)
    LED     VAR	PORTD.0 	' Alias LED to PORTD.0

    buffer_size	CON	32		' Sets the size of the ring buffer
    buffer	VAR	BYTE[buffer_size]	' Array variable for holding received characters
    index_in	VAR	BYTE	' Pointer - next empty location in buffer
    index_out	VAR	BYTE	' Pointer - location of oldest character in buffer
    bufchar	VAR	BYTE		' Stores the character retrieved from the buffer
    i		VAR	BYTE		' loop counter 
    errflag	VAR	BYTE		' Holds error flags

    CMCON=%00000111		' Disable Comparators
    TRISA=%00000000		' PORTA all set to Output 
    TRISB=%11111111		' PORTB all set to Input
    T0CON=%00000111     ' OFF,16BIT,PRESCALE=256
    ADCON0 = 0
    CMCON=7
    INTCON.5=1          'T0IE : TMR0 Overflow Interrupt Enable bit

ON interrupt GOTO GestIntrerupts        ' Deal with interrupts

ReadSerial:
   DataRec var byte[5] : DataRec = 0
   PIE1.5 = 1   			' Enable interrupt on USART
   While CounterA <= 70 : WEND
   PIE1.5 = 0				' Disable interrupt on USART
        
   FOR COUNTERB=0 to COUNTERA
        SEROUT2 SerWRT,16416,[SerDATA(COUNTERB)]
        NEXT COUNTERB

   Goto ReadReadyLoop 


' Subroutines
Disable					' Don't check for interrupts in this section

getbuf:					' move the next character in buffer to bufchar
	index_out = (index_out + 1)			' Increment index_out pointer (0 to 63)
	IF index_out > (buffer_size-1) Then index_out = 0	' Reset pointer if outside of buffer
	bufchar = buffer[index_out]			' Read buffer location
Return

error:					' Display error message if buffer has overrun
	errflag = 0			' Reset the error flag
	CREN = 0			' Disable continuous receive to clear overrun flag
	CREN = 1			' Enable continuous receive
	GoTo display		' Carry on

buffer_error:
	errflag.1 = 1		' Set the error flag for software
' Move pointer back to avoid corrupting the buffer. MIN insures that it ends up within the buffer.	
	index_in = (index_in - 1) MIN (buffer_size - 1)	
	HSerin [buffer[index_in]]	' Overwrite the last character stored (resets the interrupt flag)

usart_error:
	errflag.0 = 1		' Set the error flag for hardware
Resume					' Return to program

GestIntrerupts:
    IF INTCON.2 = 1 then
        T0CON.0 = 0 ' Disable timer
        TMR0L = 0   ' Reset timer
        TMR0H = 0   ' Reset timer
        TimeCount = TimeCount + 1
        T0CON.0 = 1 ' Enabled timer
        INTCON.2 = 0
    ELSE : IF RCIF = 1 THEN
        IF OERR Then usart_error			' Check for USART errors
	    index_in = (index_in + 1)			' Increment index_in pointer (0 to 63)
	    IF index_in > (buffer_size-1) Then index_in = 0	'Reset pointer if outside of buffer
	    IF index_in = index_out Then buffer_error	' Check for buffer overrun
	    HSerin [buffer[index_in]]			' Read USART and store character to next empty location
        SEROUT2 SerWRT,16416,[buffer(index_in)]
        SerData(CounterA)=buffer(index_in)
        CounterA = CounterA + 1	    
	    IF RCIF Then GestIntrerupts   		' Check for another character while we're here 
    ENDIF : ENDIF
    resume
ENABLE

Any input is appreciated!

[skimask]

DISABLE before here
ENABLE after your interrupt subroutine
Jump over your interrupt subroutine with a Goto Main or something
ON interrupt GOTO GestIntrerupts        ' Deal with interrupts
ReadSerial:
   DataRec var byte[5] : DataRec = 0 : PIE1.5 = 1
   While CounterA <= 70 : WEND
   PIE1.5 = 0				' Disable interrupt on USART
   FOR COUNTERB=0 to COUNTERA:SEROUT2 SerWRT,16416,[SerDATA(COUNTERB)]:NEXT COUNTERB
   Goto ReadReadyLoop 
Not really a good idea inside an interrupt subroutine
' Subroutines
Disable				' Don't check for interrupts in this section
getbuf:				' move the next character in buffer to bufchar
index_out = (index_out + 1):IF index_out > (buffer_size-1) Then index_out = 0
bufchar = buffer[index_out]:Return
error:     errflag = 0:CREN = 0:CREN = 1:GoTo display		' Carry on
buffer_error:
errflag.1 = 1:index_in = (index_in - 1) MIN (buffer_size - 1):HSerin [buffer[index_in]]
usart_error:     errflag.0 = 1		' Set the error flag for hardware
Resume					' Return to program
GestIntrerupts:
IF INTCON.2 = 1 then
T0CON.0 = 0:TMR0L = 0:TMR0H = 0:TimeCount = TimeCount + 1:T0CON.0 = 1:INTCON.2 = 0
ELSE COLON isn't needed but IF RCIF = 1 THEN moved to next line is needed : IF RCIF = 1 THEN
IF OERR Then usart_error			' Check for USART errors
index_in = (index_in + 1):IF index_in > (buffer_size-1) Then index_in = 0
IF index_in = index_out Then buffer_error	' Check for buffer overrun
HSerin [buffer[index_in]]:SEROUT2 SerWRT,16416,[buffer(index_in)]:SerData(CounterA)=buffer(index_in)
CounterA = CounterA + 1	    
IF RCIF Then GestIntrerupts   		' Check for another character while we're here 
ENDIF : ENDIF
resume
ENABLE

Where is your main loop?
You're using HSerIn with interrupts. HSerIn will wait for the NEXT character into the USART receive register after the interrupt trips.
Lots of little problems with this code...rework it a bit, straighten it out, actually READ thru it from top to bottom and see how it executes, repost, and we'll work it from there...

[johnmiller]

Well how would you suggest me to do it? Should I use serin2 instead of hserin?
I need it to be a interrupt driven buffer serial read since if I send the data too quickly it just discards some data. I tried to read the date with serin, serin2 and now hserin. My only problem now is

   PIE1.5 = 1          ' Enable interrupt on USART
   While CounterA <= 70 : WEND
   PIE1.5 = 0		   ' Disable interrupt on USART

[skimask]

Well how would you suggest me to do it? Should I use serin2 instead of hserin?

Any one of the SerIn functions can catch data very quickly, even at 19,200 and much higher. It mostly depends on how much time you actually need to process that data once received. Like I said, re-read thru your code, figure out what you really NEED vs. what you want to do. Write down a 'quick-n-dirty' flowchart of how you want/need things to work.
What are you buffering the serial port for?
Is this a FIFO or a LIFO type buffer (probably FIFO type)?
What is the main function of the program going to be? What is this program going to do for you?

[mister_e]

1. i don't see any PIC #
2. i don't see any config fuses.
3. I don't see any INTCON and other interrupt related registers

Fast reading of your code but it may work. now just comment out your whole ISR and toggle a led in and then clear RCIF falg by reading RCREG untill it's empty.

Is the thing work or not? If not, your baudrate, config fuses and or hardware is faulty.

Easier way, HSERIN/HSEROUT to echo your incomming data to you PC.

Is this working or not?

[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

[skimask]

I don't think pasting 80 pages will do any good
I really don't understand what's wrong with my code

And I guess neither will we...

[mister_e]

here's the plan... shrink the whole thing and test with a simple program... simple main loop (led blinking or else) + USART INT. Then post the whole new thing.

[johnmiller]

Ok. I managed to do my work with this (after a lot of struggle) but it works. Hope this code will help somebody in the future

PS: Thanks guys for the help

ReadSerial:
   DataRec var byte[6]
   for counterB=0 to 5
       DataRec(counterB)=0
       next counterB
   
   While CounterA <= 254
        HSERIN [serdata2]
        DataRec(0)=DataRec(1)
        DataRec(1)=DataRec(2)
        DataRec(2)=DataRec(3)
        DataRec(3)=DataRec(4)
        DataRec(4)=DataRec(5)
        DataRec(5)=serdata2
        
        IF DataRec(0)=$20 AND DataRec(2)="K" AND DataRec(3) = "E" AND DataRec(4) = "Y" THEN
           ' Parse serial data (command entered)
           SerData(CounterA) = serdata2
           CounterA = CounterA + 1
        endif
   wend

   FOR COUNTERB=0 to COUNTERA
        SEROUT2 SerWRT,16416,[SerDATA(COUNTERB), 10, 13]
        NEXT COUNTERB
   Goto MainLoop

[mister_e]

While / Wend was in the bug list right?

Seems good to me.