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.
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