PIC16F627/8（或PIC类）与DS18B20通信的程序

; Program 1820.asm
;
; Performs temperature measurment. No addressing.
;
; Note that in this routine, the results of the measurement are written
; to a data buffer beginning at data location 18H for later display or
; other processing.
;
; 12C509 DS1820
; GPIO.0 (term 7) ------------------------------ DQ (term 2)
;


LIST p=12C509A
#include
__CONFIG _CP_OFF & _WDT_OFF & _MCLRE_OFF & _IntRC_OSC


CONSTANT DATA_PIN=0

CONSTANT BASE_VAR=07H

CONSTANT DATA_BUFF=18H
CONSTANT BUFF_SIZE=7


PIN_DIRS EQU BASE_VAR+0
N EQU BASE_VAR+1

_N EQU BASE_VAR+2 ; these vars used by the
O_BYTE EQU BASE_VAR+3 ; common 1-wire routines
I_BYTE EQU BASE_VAR+4
LOOP3 EQU BASE_VAR+4
LOOP2 EQU BASE_VAR+5
LOOP1 EQU BASE_VAR+6
TEMP EQU BASE_VAR+7


TEMP_MSB EQU DATA_BUFF+0 ; first location in DATA_BUFF
TEMP_LSB EQU DATA_BUFF+1
TH_UB1 EQU DATA_BUFF+2
TL_UB2 EQU DATA_BUFF+3
COUNT_REM EQU DATA_BUFF+4
COUNT_D_C EQU DATA_BUFF+5
CRC EQU DATA_BUFF+6

ORG 000H

MAIN:
MOVLW 0C0H ; GPWU dis, GPPU dis, other bits are not used
OPTION

MOVLW 1FH
MOVWF PIN_DIRS ; make all I/Os inputs
TRIS GPIO

CALL INIT ; intitialize DS1820

MOVLW 0CCH ; skip ROM
MOVWF O_BYTE
CALL OUT_BYTE

MOVLW 44H ; perform temperature conversion
MOVWF O_BYTE
CALL OUT_BYTE

CALL STRONG_PULL_UP ; provide strong pull up during conversion

WAIT:
CALL IN_BYTE
MOVLW 0FFH
SUBWF I_BYTE, W
BTFSS STATUS, Z
GOTO WAIT

CALL INIT

MOVLW 0CCH ; skip ROM
MOVWF O_BYTE
CALL OUT_BYTE

MOVLW 0BEH ; read scratchpad
MOVWF O_BYTE
CALL OUT_BYTE

CALL IN_BYTE ; fetch each byte and save
MOVF I_BYTE, W
MOVWF TEMP_LSB

CALL IN_BYTE
MOVF I_BYTE, W
MOVWF TEMP_MSB

CALL IN_BYTE
MOVF I_BYTE, W
MOVWF TH_UB1

CALL IN_BYTE
MOVF I_BYTE, W
MOVWF TL_UB2

CALL IN_BYTE ; throw these two away
CALL IN_BYTE

CALL IN_BYTE
MOVF I_BYTE, W
MOVWF COUNT_REM

CALL IN_BYTE
MOVF I_BYTE, W
MOVWF COUNT_D_C

CALL IN_BYTE
MOVF I_BYTE, W
MOVWF CRC

DISPLAY:
; not implemented. At this point data is located in seven
; bytes beginning at 18H.

DELAY_30_SEC:

MOVLW .120 ; 30 second delay (120 * 250 msecs)
MOVWF LOOP3
DELAY_30_1
CALL DELAY_LONG
DECFSZ LOOP3, F
GOTO DELAY_30_1

GOTO MAIN ; do it again


; The following are standard 1-Wire routines.

INIT:
CALL PIN_HI
CALL PIN_LO

MOVLW .50 ; 500 us delay
CALL DELAY_10USEC

CALL PIN_HI
MOVLW .50 ; 500 usec delay
CALL DELAY_10USEC

RETURN


IN_BYTE: ; returns byte in W
MOVLW .8
MOVWF _N
CLRF I_BYTE

IN_BYTE_1:
CALL PIN_LO ; momentary low on DATA_PIN
NOP
CALL PIN_HI
NOP
NOP
NOP
NOP
NOP
NOP
MOVF GPIO, W ; 7 usecs later, fetch from DATA_PIN
MOVWF TEMP
BTFSS TEMP, DATA_PIN
BCF STATUS, C ; its a zero
BTFSC TEMP, DATA_PIN
BSF STATUS, C ; its a one

RRF I_BYTE, F
MOVLW .6 ; now delay 60 usecs
CALL DELAY_10USEC
DECFSZ _N, F
GOTO IN_BYTE_1

MOVF I_BYTE, W ; return the result in W
RETURN

OUT_BYTE:
MOVLW .8
MOVWF _N
OUT_BYTE_1:
RRF O_BYTE, F
BTFSS STATUS, C
GOTO OUT_0
GOTO OUT_1
OUT_BYTE_2:
DECFSZ _N, F
GOTO OUT_BYTE_1
RETURN

OUT_0:
CALL PIN_LO ; bring DATA_PIN low
MOVLW .6 ; for 60 usecs
CALL DELAY_10USEC
CALL PIN_HI
GOTO OUT_BYTE_2

OUT_1:
CALL PIN_LO ; momentary low
CALL PIN_HI
MOVLW .6
CALL DELAY_10USEC
GOTO OUT_BYTE_2

;;;;;;

PIN_HI:
BSF PIN_DIRS, DATA_PIN
MOVF PIN_DIRS, W
TRIS GPIO

RETURN

PIN_LO:
BCF GPIO, DATA_PIN
BCF PIN_DIRS, DATA_PIN
MOVF PIN_DIRS, W
TRIS GPIO

RETURN

STRONG_PULL_UP:
BSF GPIO, DATA_PIN
BCF PIN_DIRS, DATA_PIN
MOVF PIN_DIRS, W
TRIS GPIO
CALL DELAY_LONG
BSF PIN_DIRS, DATA_PIN
MOVF DATA_PIN, W
TRIS GPIO
RETURN


DELAY_LONG
MOVLW .250 ; 250 msec delay
MOVWF LOOP1
DELAY_N_MS:
OUTTER
MOVLW .110 ; close to 1.0 msec delay when set to .110
MOVWF LOOP2
INNER
CLRWDT
NOP
NOP
NOP
NOP
NOP
DECFSZ LOOP2, F ; decrement and leave result in LOOP2
; skip next statement if zero
GOTO INNER
DECFSZ LOOP1, F
GOTO OUTTER
RETURN

DELAY_10USEC: ; provides a delay equal to W * 10 usecs
MOVWF LOOP1
DELAY_10USEC_1:
CLRWDT
NOP
NOP
NOP
NOP
NOP
NOP
DECFSZ LOOP1, F
GOTO DELAY_10USEC_1
RETURN

END

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