Circuit reliability issues

[Archangel]

Hi hkpatrice,
have you tried installing a capacitor on your MCLR pin to ground to hold the PIC in a reset condition until the chip settles down internaly?
I see no TRISE statement in code . . . Probably need this so chip knows input or outputs.

[hkpatrice]

Joe s. said:

"Hi hkpatrice,
have you tried installing a capacitor on your MCLR pin to ground to hold the PIC in a reset condition until the chip settles down internaly? I see (at least I think I see) you are feeding the mclr pin through a resistor from the 24 volt line and limiting the voltage with a zener, I am wondering if that zener is introducing noise from it's constant switching, cycling the voltage up/down. . . How does it work on a 5v regulated supply?"

Hello Joe and thanks for the quick answer.

-I haven't tried putting a cap on the MCLR line, however, I have the power-up timer enabled, doesn't that play a similar role?

-The MCLR pin is fed through a resistor from the 5V rail, not the 24V one... And no zener there... Sorry for the quality of the BMP, it's the best I could do while staying under the 200Kb limit.

-You are right about the missing TRISE statement! How could I miss that? Could that be the cause of the problems I've been experiencing?

Thanks for the input!

[mister_e]

can you try to use PrimoPDF to post your Schematic?
http://www.primopdf.com/

PrimoPDF is free and really nice, not sure 'bout the final PDF size so far

It also seems to have something to do with the ISR, about DISABLE/ENABLE/RESUME 'round your ISR

[hkpatrice]

mister_e,

Thanks for the suggestion, I tried convertingthe file to PDF but it still comes in at 370Kb...
Still too much to post on here.

Please tell me more about this interrupt handling issue, you seem to have spotted something that eludes me. Of course, If the problem was with the ISR, then it would cause the erratic behavior I've been experiencing...

Thanks for the help!

[mister_e]

Try to ZIP your PDF, or send it to my e-mail.

The most notable place to use DISABLE is right before the actual interrupt handler. Or the interrupt handler may be placed before the ON INTERRUPT statement as the interrupt flag is not checked before the first ON INTERRUPT in a program.

ON INTERRUPT GOTO serialin		' Declare interrupt handler routine
        '
        '
        '
        '
' 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
	ADDRESS = addressbuffer[index_out]			' Read buffer location
	COMMAND = commandbuffer[index_out]
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 main		' Carry on
	
	
' Interrupt handler
        '        Where's the Disable???
serialin:				' Buffer the character received
IF PIR1.5=1 THEN                        'IF THIS IS A USART INTERRUPT....   
	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 badparity,10,badparity,[addressbuffer[index_in],commandbuffer[index_in]]          		' Read USART and store character to next empty location
	IF RCIF THEN serialin				' Check for another character while we're here
ENDIF
	
RESUME					' Return to program

badparity:
IF index_in=0 THEN
index_in= (buffer_size-1)
ELSE
	index_in = (index_in - 1) 	 ' Move pointer back to avoid corrupting the buffer.
ENDIF
GOTO main

        '        You don't even need it as you used HSER_CLROERR define.
        '        Let's say CLROERR don't work, YOU DON'T WANT TO use a GOTO inside the ISR 
        '        or you'll experiment a stack overflow/underflow one day or another.  Same rule apply in badparity sub.. which is also called somewhere in the main loop
usart_error:
  errflag=1
  GOTO main


buffer_error:
	errflag.1 = 1		' Set the error flag for software
IF index_in=0 THEN
index_in= (buffer_size-1)
ELSE
	index_in = (index_in - 1) 	 ' Move pointer back to avoid corrupting the buffer.
ENDIF	
	
RESUME					' Return to program

MAYBE it's safe to place Disable BEFORE the ISR as long as there's another ENABLE somewhere after, but i don't see any

Maybe there's something else, those are the first who jump in my face.

HTH