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PIC Microcontoller Program Flow Methods

for string matching

Carlos Nieves shares this code:


Here are some routines to match strings received from serial communications or other routines.
Known strings are stored in program memory, thus saving RAM locations. These routines let you to check a string while you are receiving it, and return an identifier for the received string, if it's known.
The main limitation is that there should be enough time between receiving two characters, so the routine could finish. This shouldn't be a problem in micros with USART, but must be taken into account in micros without it.

This routines require some flags handling routines, which you could find here.

The code begin here:

;  Copyright (C) 2001  Carlos Nieves Onega 

;  This program is free software; you can redistribute it and/or modify
;  it under the terms of the GNU General Public License as published by
;  the Free Software Foundation; either version 2 of the License, or
;  (at your option) any later version.

;  This program is distributed in the hope that it will be useful,
;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;  GNU General Public License for more details.

;  You should have received a copy of the GNU General Public License
;  along with this program; if not, write to the Free Software
;  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

;**********************************************************************
;                                                                     
;    File:	    str.asm                                           
;    Version:       20011030
;                                                                     
;    Author:   Carlos Nieves Onega                                     
;    	                                                              
;                                                                      
;                                                                     
;**********************************************************************
;                                                                     
;	Required files:                                          
;		Flags handle routines (flags.asm, 20011026)
;                                                                     
;**********************************************************************
;                                                                     
;    Notes:   This file contains routines to handle strings.
;             Strings must be in a single block in program memory.
;                                                                     
;**********************************************************************
; Changes:
;	20011030 (cnieves): modified get_id_str_serie so it doesn't care about 
;			CR y LF characters.
;	20011029 (cnieves): began writing.
;			Functions tested:
;				getchar_strrom and get_id_str_serie.
;			Simulated. They work fine.
;**********************************************************************

;**********************************************************************
; Strings to be compared must be stored in a single block in memory.
; For each string, it must be stored, sorted as shown, the following:
;	* String length (1 byte): number 'n' of characters of the string.
;	* String Id. (1 byte): there mustn't be two strings with the same id.
;		Id must be greater than 0. The ids. begin with number 1 and 
;		must be correlative.
;	* Characters of the string: ( 'n' bytes).
;**********************************************************************
CADS_ADDR
		TABLE_JUMP
ID_CAD	set 	1
				;   Length     Identifier     String
CAD1	equ	ID_CAD
				DT	d'4',	ID_CAD, 	"CAD1"
ID_CAD	set	ID_CAD + 1
CAD2	equ	ID_CAD
				DT	d'12',	ID_CAD,		"This is cad2"
; The last string mustn't increase ID_CAD

; Define CADS_NUM, which will be necessary to reserve space for flags.
#define		CADS_NUM	ID_CAD


;**********************************************************************
;	Function getchar_strrom
;	Description: given the id. of the string, returns the character 
;		at the position given in WREG (begun with 0).
;	Parameters:
;		WREG: position of the character within the string (the first one is 0).
;		ID_CAD_GC: string id.. Always must be greater than 0.
;	Returns:
;		WREG: character at the given position. If the id. was not found
;		or if the length is less than the given position, returns 0xFF
;		Z = 1	: operation not valid (string or position invalid).
;		Z = 0	: operation completed succesfully.
;	Use:
;		var. temp. num_cad, id_cad, pos_char.
;		regs. W, INDF, FSR
;**********************************************************************
	cblock
CAD_NUM_GC:	1
ID_CAD_GC:	1
POS_CHAR_GC:	1
TABLE_POS_GC:	1
	endc

getchar_strrom
		movwf	POS_CHAR_GC
		clrf	TABLE_POS_GC
		movlw	CADS_NUM
		addlw	1		; Adds 1 because of the loop particularities
		movwf	CAD_NUM_GC	; num_cad = number of strings stored
BUC_GC		
		decfsz	CAD_NUM_GC,F
		goto	LABEL1_GC
		goto	NO_ENC_GC	; If all strings were looked, it was not found.
LABEL1_GC		
		movlw	d'1'
		addwf	TABLE_POS_GC,W	; W points to the string id.
		call	CADS_ADDR	
					; W = string id.
		xorwf	ID_CAD_GC,W	; compare the string id. with the parameter
		bz	ENC_GC		; If it's 0, the string was found
		
		movf	TABLE_POS_GC,W	; W = pointer to the length
		call	CADS_ADDR
					; W = length of the string
		addwf	TABLE_POS_GC,F	; TABLE_POS_GC += string length
		movlw	d'2'
		addwf	TABLE_POS_GC,F	; TABLE_POS_GC += 3 (length, identifier)
					; with this, TABLE_POS_GC points to the "struct" of the next string
		goto	BUC_GC
		

ENC_GC		
		movf	TABLE_POS_GC,W
		call	CADS_ADDR
					; W = length
		subwf	POS_CHAR_GC,W	; W = position (began with 0) - length (began with 1)
		bc	NO_ENC_GC

		movlw	d'2'	
		addwf	TABLE_POS_GC,F	; FSR points to the beginning of the string

		movf	POS_CHAR_GC,W
		addwf	TABLE_POS_GC,W	; FSR points to the wanted character
		call	CADS_ADDR	
					; W = character
		bcf	STATUS,Z
		return

NO_ENC_GC	
		movlw	0xff
		bsf	STATUS,Z
		return



;**********************************************************************
;	Function get_id_str_serie
;	Description: Returns in WREG the id. of the string received
;		from the serial port (or 0 if it doesn't match).
;	Parameters: none
;	Return:
;		WREG: identifier of the received string. (0 if it's none of the stored).
;	Use:
;		Flags handle routines: set_all_flags, count_flags, look_flag
;**********************************************************************
	cblock
NUM_CHAR_GISS:	1
NUM_CAD_GISS:	1
CHAR_SERIE:	1
TEMP_GISS:	1
	endc

REC_SALE_GISS	decfsz	TEMP_GISS,1
		goto	REC_BUC_GISS
		retlw 	0
get_id_str_serie
		call	set_all_flags	; By now, all strings are valid. FIXME: only set those related with strings
		clrf	NUM_CHAR_GISS	; Initialice the character to look to 0.
BUC_OTRO_CHAR_GISS
		movlw	0x80		;Times to wait for a serial character
		movwf	TEMP_GISS	
REC_BUC_GISS	
		call	RX_SERIE 	; getchar(serie) You should change this to your needs.
		iorlw	0               
		bz	REC_SALE_GISS
		movf	DATA_IN,w

		movwf	CHAR_SERIE
		movlw	CR
		xorwf	CHAR_SERIE,W
		bz	BUC_OTRO_CHAR_GISS	; If it's CR, ignore it
		movlw	LF
		xorwf	CHAR_SERIE,W
		bz	BUC_OTRO_CHAR_GISS	; If it's LF, ignore it

		movlw	d'1'
		movwf	NUM_CAD_GISS	; String Id. to analyze
BUC_CAD_GISS
		movlw	d'1'
		subwf	NUM_CAD_GISS,W
		call	look_flag
		bz	OTRA_CAD_GISS
		
		movf	NUM_CAD_GISS,W
		movwf	ID_CAD_GC	; ID_CAD_GC = Id. to look
		movf	NUM_CHAR_GISS,W	; W = number of character to test
		call	getchar_strrom
		addlw	d'0'
		bz	ENC_GISS	; If this character is 0 (string end), it was founded
		xorwf	CHAR_SERIE,W	; compare it with the received character.
		bnz	NO_CAD_GISS	; If they don't match, this string is not valid.

		movf	NUM_CAD_GISS,W
		movwf	ID_CAD_GC	; ID_CAD_GC = Id. to look
		movlw	d'1'
		addwf	NUM_CHAR_GISS,W	; W = number of the character to look + 1
		call	getchar_strrom	; Look the next character.
		xorlw	0xff
		bz	ENC_GISS	; If it's 0xff (string end), it was founded
		goto	OTRA_CAD_GISS

NO_CAD_GISS	movlw 	d'1'
		subwf	NUM_CAD_GISS,W
		call	clr_flag
		goto 	OTRA_CAD_GISS

OTRA_CAD_GISS
		call	count_flags	; Look how many strings were not compared yet.
		addlw	d'0'
		bz	NO_ENC_GISS	; If none, then it was not founded.

		movlw	d'1'
		addwf	NUM_CAD_GISS,F
		movlw	CADS_NUM
		subwf	NUM_CAD_GISS,W	; Compare the string id. de cadena to look with the number of strings
		bnc	BUC_CAD_GISS	; Si it's negative (C=0), continues testing the next string
		bz	BUC_CAD_GISS	; idem if it's zero

		movlw	d'1'
		addwf	NUM_CHAR_GISS,F	; NUM_CHAR_GISS++ (looks the next character)
		goto 	BUC_OTRO_CHAR_GISS

NO_ENC_GISS
		retlw	0
ENC_GISS
		movf	NUM_CAD_GISS,W
		return


  

See also:


file: /Techref/microchip/string_matching.htm, 9KB, , updated: 2003/1/26 13:51, local time: 2017/11/20 11:31,
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