A simple thermometer circuit display used to display the value of the temperature sensing for 10 k ntc also relay output the relay can be backed by sustained with the transistor has very little material can be accomplished with
Thermometer Circuit Schematic
Thermometer Circuit Assembly code
list p=pic16c74
__config h'3ffa' ;HS crystal, 20Mhz
include
;
temp equ 0x20
target equ 0x21 ;target temp value to trigger relay
targdly equ 0x22 ;used to pause display when setting target
flag equ 0x23
cntr equ 0x24
;
org 0 ;reset vector
goto start ;go to beginning of program on reset
;
org 4
btfsc PIR1,TMR1IF ;timer 1 overflowed?
goto timer1
retfie
;
start movlw 0xbf ;'-' segment value
movwf PORTB ;set output
movwf PORTD ;latches to initial value
clrf PORTA ;clear port a latches
bsf STATUS,RP0 ;select register bank 1
clrf PIE1 ;disable all peripheral interrupts
bsf TRISC,0 ;RC0 needs to be input for osc to function
bsf PIE1,TMR1IE ;enable TMR1 int
movlw b'00000011' ;RA0=A/D input, RA1=A/D input, RA2=Relay output
movwf TRISA ;porta all input/analog
clrf TRISB ;PORTB/PORTD output to 7-segment LEDs
clrf TRISD
movlw 0x04 ;RA0 and RA1 Analog, RA2 Digital, Vref=Vdd
movwf ADCON1 ;set
bcf STATUS,RP0 ;select register bank 0
bcf T1CON,TMR1ON ;timer 1 not on
movlw 0x80 ;TIM1H:TIM1L = 0x8000 = 1sec
movwf TMR1H
clrf TMR1L
clrf INTCON ;disable all interrupts
clrf PIR1 ;clear all falgs
movlw 0x0e ;T1CKPS1 (Prescale) = 1, T1OSCEN (osc shutoff) = enabled
movwf T1CON ;T1SYNC (ext clk input) = no sync, TMR1CS = external
bsf INTCON,PEIE ;enable peripheral interrupts
bsf INTCON,GIE ;enable global ints
call getAD1 ;get target temp value
movwf target ;save for compare
clrf targdly ;clear target display counter
clrf flag ;to tell which a/d to perform, RA0 or RA1
bsf T1CON,TMR1ON ;turn timer on
sleep
goto $-1
;
timer1 bcf PIR1,TMR1IF ;clear flag
bcf INTCON,GIE ;disable all ints
movlw 0x01 ;halfadd value
xorwf flag,1 ;compute operation to perform
movf flag,0
addwf PCL,1 ;go to proper routine
goto trgsamp
goto temsamp
trgsamp call getAD1 ;get target value
movwf temp
subwf target,0 ;check it
btfsc STATUS,Z ;zero set if equal, same target
goto timerx
movf temp,0 ;get new target value
movwf target
movlw 0x01
movwf flag ;do trigger sample next go around also
goto dispit
temsamp call getAD0 ;get RA0 thermister value
movwf temp
subwf target,0
btfss STATUS,C
bsf PORTA,2 ;trigger relay, temp has reached goal
dispit movlw .186
subwf temp,0 ;end of table values
btfsc STATUS,C
goto valerr ;error, value out of range
movlw .98 ;base of table values
subwf temp,0
btfss STATUS,C ;if carry clear then
goto valerr ;error, value out of range
call temptab ;convert to temp
setleds movwf temp
andlw 0x0f
call ledtab
movwf PORTB
swapf temp,0
andlw 0x0f
call ledtab
movwf PORTD
timerx bcf PIR1,TMR1IF ;clear flag
movlw 0x80
movwf TMR1H
clrf TMR1L
retfie ;enable ints and return to sleep
valerr movlw 0xaa ;0x0a is disp in ledtab to special out of range value
goto setleds
getAD0 movlw b'10000001' ;fosc/32, chan0 (RA0), ADON
adconv movwf ADCON0
clrf cntr
decfsz cntr,1
goto $-1
clrf cntr
decfsz cntr,1
goto $-1
bsf ADCON0,GO
btfsc ADCON0,NOT_DONE ;check if A/D complete
goto $-1
movf ADRES,0
clrf ADCON0 ;clear reg and shutdown AD logic
return
getAD1 movlw b'10001101' ;fosc/32, chan1 (RA1), GO, ADON
goto adconv
;
; 7-segment conversion
;
ledtab addwf PCL,1
retlw 0xc0 ;0
retlw 0xfc ;1
retlw 0x92 ;2
retlw 0x98 ;3
retlw 0xac ;4
retlw 0x89 ;5
retlw 0x81 ;6
retlw 0xdc ;7
retlw 0x80 ;8
retlw 0x8c ;9
retlw 0xbf ;-
;
;tempature table
;
temptab addwf PCL,1
retlw 0x99 ;98
retlw 0x98 ;99
retlw 0x98 ;100
retlw 0x97 ;101
retlw 0x96 ;102
retlw 0x95 ;103
retlw 0x94 ;104
retlw 0x93 ;105
retlw 0x93 ;106
retlw 0x92 ;107
retlw 0x91 ;108
retlw 0x90 ;109
retlw 0x89 ;110
retlw 0x89 ;111
retlw 0x88 ;112
retlw 0x87 ;113
retlw 0x86 ;114
retlw 0x86 ;115
retlw 0x85 ;116
retlw 0x85 ;117
retlw 0x84 ;118
retlw 0x83 ;119
retlw 0x82 ;120
retlw 0x81 ;121
retlw 0x80 ;122
retlw 0x80 ;123
retlw 0x79 ;124
retlw 0x78 ;125
retlw 0x78 ;126
retlw 0x77 ;127
retlw 0x76 ;128
retlw 0x76 ;129
retlw 0x75 ;130
retlw 0x74 ;131
retlw 0x73 ;132
retlw 0x72 ;133
retlw 0x71 ;134
retlw 0x70 ;135
retlw 0x70 ;136
retlw 0x69 ;137
retlw 0x69 ;138
retlw 0x68 ;139
retlw 0x67 ;140
retlw 0x67 ;141
retlw 0x66 ;142
retlw 0x65 ;143
retlw 0x64 ;144
retlw 0x63 ;145
retlw 0x62 ;146
retlw 0x62 ;147
retlw 0x61 ;148
retlw 0x60 ;149
retlw 0x59 ;150
retlw 0x59 ;151
retlw 0x58 ;152
retlw 0x58 ;153
retlw 0x57 ;154
retlw 0x56 ;155
retlw 0x55 ;156
retlw 0x54 ;157
retlw 0x53 ;158
retlw 0x53 ;159
retlw 0x52 ;160
retlw 0x51 ;161
retlw 0x51 ;162
retlw 0x50 ;163
retlw 0x49 ;164
retlw 0x49 ;165
retlw 0x48 ;166
retlw 0x47 ;167
retlw 0x46 ;168
retlw 0x45 ;169
retlw 0x44 ;170
retlw 0x44 ;171
retlw 0x43 ;172
retlw 0x42 ;173
retlw 0x41 ;174
retlw 0x40 ;175
retlw 0x39 ;176
retlw 0x39 ;177
retlw 0x38 ;178
retlw 0x37 ;179
retlw 0x37 ;180
retlw 0x36 ;181
retlw 0x35 ;182
retlw 0x34 ;183
retlw 0x33 ;184
retlw 0x32 ;185
retlw 0x32 ;186
end
Published: 2009/02/02 Tags: microchip projects, microcontroller projects, pic assembly example
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