Post by thread:[PIC]: Character compare and XOR'ing

Heyas, Still working on a serial interfaced traffic light. Using a recurring XOR to test the chars I saw in an earlier post. The problem is that it will only turn on the Red LED (PortB.0), regardless of the input character. I am sending the w register through the serial port as a test to see what characters are coming back, and I get the same set for any order of inputs. R- G8 Y& So it is doing something to the bits in w, and it does the same thing independent of order. Not sure what the - means if not null since hyphen in ascii is not 0000000? Worked through the binary math and I'm pretty sure that the way I have it set up it should hit on the correct characters, but it seems like all characters are being interpreted as "R", or something else is busted. Thanks! //===== Code Below ===== LIST P=16F876, R=DEC INCLUDE "p16F876.inc" __CONFIG _CP_OFF & _HS_OSC & _PWRTE_ON & _WDT_OFF & _BODEN_ON ; Mainline org 0 bsf STATUS, RP0 ; Enable the Serial Port, bank 1 movlw (1 << TXEN) ; Enable Serial Transmission movwf TXSTA ^ 0x080 movlw 51 ; Serial Port running at 1200baud movwf SPBRG ^ 0x080 bcf TRISB ^ 0x080, 0 ; Set PortB 0.1.2 to output bcf TRISB ^ 0x080, 1 bcf TRISB ^ 0x080, 2 bcf STATUS, RP0 ; Return to bank 0 movlw (1 << SPEN) | (1 << CREN) movwf RCSTA ; Enable Serial I/O Loop btfss PIR1, RCIF ; Wait for rx character set goto Loop ; Nothing there movf RCREG, 0 ; Get rx character bcf PIR1, RCIF ; Clear the Character Present Flag XORWF 'R', w ; Is the character R? BTFSS STATUS, Z call GORED XORWF ('Y'^'R'), w ; No? Is the character Y? BTFSS STATUS, Z call GOYEL XORWF ('G'^'Y'), w ; No? Is the character G? BTFSS STATUS, Z call GOGRN ; Else it is not R, Y, or G bsf PORTB, 0 ; Invalid Character, light all LEDs bsf PORTB, 1 bsf PORTB, 2 goto Loop ; Subroutines GORED: ; Turn on Red LED bsf PORTB, 0 bcf PORTB, 1 bcf PORTB, 2 movwf TXREG goto Loop ;return GOYEL: ; Turn on Yellow LED bcf PORTB, 0 bsf PORTB, 1 bcf PORTB, 2 movwf TXREG goto Loop ;return GOGRN: ; Turn on Green LED bcf PORTB, 0 bcf PORTB, 1 bsf PORTB, 2 movwf TXREG goto Loop ;return end -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> XORWF 'R', w ; Is the character R? > BTFSS STATUS, Z > call GORED > XORWF ('Y'^'R'), w ; No? Is the character Y? > BTFSS STATUS, Z > call GOYEL > XORWF ('G'^'Y'), w ; No? Is the character G? > BTFSS STATUS, Z > call GOGRN Unless you really really need the speed from a small number of choices, use a table. That will be much easier to maintain. Note that you have each command character code in two places with your method. See my HOS_CMD.ASPIC module in my HOS project at http://www.embedinc.com/pic/hos.htm for an example of a table driven command dispatch routine. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

----- Original Message ----- From: "Olin Lathrop" <olin_piclistKILLspamEMBEDINC.COM> To: <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Sent: Saturday, April 05, 2003 12:02 PM Subject: Re: [PIC]: Character compare and XOR'ing {Quote hidden}> > XORWF 'R', w ; Is the character R? > > BTFSS STATUS, Z > > call GORED > > XORWF ('Y'^'R'), w ; No? Is the character Y? > > BTFSS STATUS, Z > > call GOYEL > > XORWF ('G'^'Y'), w ; No? Is the character G? > > BTFSS STATUS, Z > > call GOGRN Your BTFSS STATUS,Z instructions should be BTFSC STATUS,Z Bob Ammerman RAm Systems -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> For the XORWF, shouldn't you be using XORLW since you are XORing literals > with W rather than registers? That's for sure. Use XORLW instead of XORWF Use BTFSC instead of BTFSS and you should be good to go. But be sure you understand why this as how it should be, or the time we've taken to help you out is mostly wasted. Bob Ammerman RAm Systems -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

Thanks, I think I understand now. SC skips if not equal and before I was xoring with null memory or something which is why I was getting bad results. Works like a charm. Incidentally, anyone know a good way to attach LEDs inside a case? I've been using twisted pair crimps cut in half. Couldn't locate double crimps that were small enough and reasonably priced. A friend uses wrapping wire and bonds it with glue but I'd rather use the tubes than get glue all over the place. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Sat, 5 Apr 2003 19:49:13 -0500, Chuck Rice wrote: >Thanks, I think I understand now. SC skips if not equal and before I was >xoring with null memory or something which is why I was getting bad >results. Works like a charm. > Mistakenly using SC vs SS (or vice versa) on the Z bit is something that I used to do all too frequently. Once I switched over to using the 'skpz' and 'skpnz' pseudo-ops, the problem was solved. I'd highly recommend using them. They save me from tearing out what little hair I have left. :=) Regards, Bob -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu>

Bob Ammerman <RemoveMEPICLISTTakeThisOuTmitvma.mit.edu> wrote: > Use XORLW instead of XORWF > > Use BTFSC instead of BTFSS > > and you should be good to go. Except that you'll also want to change your CALLs to GOTOs. -Andy P.S. And to avoid possible read-modify-write problems, you MIGHT want to put small delays between the BCF/BSF operations on port B in GORED, GOYEL, and GOGRN... Or delete them and just do a MOVLW xx/MOVWF PORTB after the MOVWF TXREG in each of those sections. === Andrew Warren -- spamBeGoneaiwspamBeGonecypress.com === Principal Design Engineer === Cypress Semiconductor Corporation === === Opinions expressed above do not === necessarily represent those of === Cypress Semiconductor Corporation -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu>