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; - thermistor with capacitor connected to RB2:
;
;           o +5V
;           |
;           |
;          === 470n      100R
;           |
;           |----------/\/\/\/----- RB2
;           |
;           /
;           ;           /
;           ;           |
;           |
;          GND
;
; - push button switching RB3 between +5V and GND
;
; - LCD 1x24 HD44780 connected via 4-bit interface
;          
;     D7=RB7
;     D6=RB6
;     D5=RB5
;     D4=RB4
;     D3...D0 - NC
;     R/W=RA1
;     E=RA3
;     RS=RA2

;
; - LED connected to RA0 (can be replaced with 2nd thermistor)
;
; - 4MHz crystal oscillator
;
; The 470n capacitor is charged for 500ms and then discharged
; through the thermistor.  The discharging time is measured
; by the MPU and translated to a corresponding temperature.
; The thermistor is an NTC with a resistance of 6k @ 20 C.
; The translation table is located at 0x300.  A diagram of
; temperatures in the past 16 hours is drawn in a graphical
; way using the features of definable CGRAM in the LCD
;

; This program is meant for PIC16F84, although it should work
; on a 16F83

  ERRORLEVEL      -302
  Processor       16F84
  Radix           HEX
  EXPAND

  include "p16f84.inc"

__CONFIG _CP_OFF & _XT_OSC & _PWRTE_ON  & _WDT_OFF

_ResetVector    set     0x00
_IntVector      set     0x04

LINE1                   EQU             0x080   ; Set display to line 1 (10000000)
LINE2                   EQU             0x0C0   ; Set display to line 2 (11000000)
FUNCTION_SET            EQU             0x020   ; 4 bits, 1 line, 5x7 Font
DISP_ON                 EQU             0x00C   ; Display on
DISP_ON_C               EQU             0x00E   ; Display on, Cursor on
DISP_ON_B               EQU             0x00F   ; Display on, Cursor on, Blink cursor
DISP_OFF                EQU             0x008   ; Display off
DISP_RET                EQU             0x002   ; Return to start
CLR_DISP                EQU             0x001   ; Clear the Display
ENTRY_INC               EQU             0x006   ; Increment cursor 

ENTRY_INC_S             EQU             0x007   ; Increment cursor, automatic shift
ENTRY_DEC               EQU             0x004   ; Decrement cursor
ENTRY_DEC_S             EQU             0x005   ; Decrement cursor, automatic shift
DD_RAM_ADDR             EQU             0x080   ; Least Significant 7-bit are for address
DD_RAM_UL               EQU             0x080   ; Upper Left coner of the Display
SHIFTL   EQU  0x018 ; shift left
SHIFTR   EQU  0x01C ; shift right
CGRAM_DEF  EQU  0x040 ; define CGRAM

; LCD Display Commands and Control Signal names.

E         EQU      3       ; LCD Enable control line
R_W       EQU      1       ; LCD Read/Write control line
RS        EQU      2       ; LCD Register Select control line
LED   EQU  0 ; LED
TERM   EQU  4 ; thermistor
BUTTON   EQU  3 ; push-button
;--------------------------------------------------------------------------------------------
cblock  0x00c
  Hour,Min,Char,Kind,Temp,Trans,Licznik,Value,Odjem,r1, r2, r3, r4
endc
;--------------------------------------------------------------------------------------------
org     _ResetVector        ; RESET vector location
RESET:
goto    Start
;--------------------------------------------------------------------------------------------
org     _IntVector       ; Interrupt vector location
ERROR1:
bcf     STATUS, RP0      ; Bank 0
goto    ERROR1

;--------------------------------------------------------------------------------------------
Start:
movlw d'60'   ; the diagram is updated every hour
movwf Hour
movlw d'60'
movwf Min
clrf    STATUS           ; Do initialization (Bank 0)
clrf    INTCON
bsf     STATUS, RP0      ; Bank 1
clrf    TRISA            ; RA5 -  0 outputs
movlw   0xF0           
movwf   TRISB            ; RB7 - 4 inputs, RB3 - 0 outputs
bsf     OPTION_REG, NOT_RBPU   ; Disable PORTB pull-ups
bcf     STATUS, RP0      ; Bank 0
clrf    PORTA            ; ALL PORT output should output Low.
clrf    PORTB
call    LCD_Init         ; Set up the LCD Module

;--------------------------------- MAIN LOOP ---------------------------------
loop:
call  Delay500ms  ; delay
call  Delay500ms

; ------ turn Led Off -------
bcf     STATUS, RP0      ; Select Register page 0
bcf  PORTA,LED

; ------ change RB (except RB3) to output -----------
bsf     STATUS, RP0      ; Bank 1
movlw 0x08
movwf TRISB
bcf     STATUS, RP0      ; Bank 0

bsf  PORTB,2   ; charge cap
call  Delay500ms  ; delay
call  Delay500ms

;-------- Turn Led on -----------
bsf  PORTA,LED

;-------- change RB2 to input ------------
bsf     STATUS, RP0      ; Bank 1
movlw 0x0C
movwf TRISB
bcf     STATUS, RP0      ; Bank 0
; ------- the measurement begins here ---------------------
call  DelayTInit  ; initial delay to compensate
movlw   0x1   ; resistance @ maximal temperature
movwf   Temp

;------------ measuring loop -------------------------------
clrf  Value
mierz:
bcf     STATUS, RP0     ; Bank 0

movf Temp,w   ; Temp -> W
movwf r1   ; W -> r1

btfss Value,0   ; increment Temp every fourth loop
goto contin   ; to compensate non-linearity of the thermistor
btfss Value,1
goto contin
incf Temp,1

contin:     ; keep counting until thermistor
call  DelayT   ; gets discharged
btfss PORTB,2
goto done
incfsz Value,f
goto mierz

done:
; buffer is from memory location 0x1F to 0x2F
; update the buffer with new value
; and shift buffer downwards

decfsz Min,f   ; decrease number of minutes
goto noupdate
movlw d'60'
movwf Min
decfsz Hour,f
goto  noupdate
movlw d'60'
movwf Hour

clrf Kind

; variable Kind:
; All values in buffer are negative: Kind=00000010
; All values in buffer are positive: Kind=00000001
; Both values are in buffer:         Kind=00000011

; ----------------- move new value to address 0x1E ---------------
movf Value,w
movwf 0x1E

; ---------------- shift buffer downwards ------------------
movlw 0x10
movwf  Licznik
cloop:
movf Licznik,w
addlw 0x1D
movwf FSR   ; FSR now contains address
movf INDF,w   ; get value @ FSR
incf FSR,f   ; FSR++
movwf INDF   ; save value to new FSR

movlw   HIGH GetTemp           ; PCLATH points to last page of memory
movwf   PCLATH   ; where the table sits
movf INDF, w               ;  Use the Value as an Offset
call CheckFF
call  GetTemp
movwf  Trans   ; Trans now contains real temp

movf Kind,w   ; update Kind
btfss Trans,7
iorlw 0x01
btfsc Trans,7
iorlw 0x02
movwf Kind

decfsz Licznik,f
goto cloop

; ---------------- define CGRAM of LCD depending --------------
; ---------------- on Kind (the range of values) --------------
call DefineChar

noupdate:
; return to first character in LCD
movlw  DISP_RET
call  Send_Cmd

;-------------- now display the value ----------------------

btfsc PORTB,BUTTON  ; raw calibration display of Value
goto normal
call DispBin   ; display Value in binary form
goto  loop

normal:     ; normal reading through table
movlw   HIGH GetTemp           ; PCLATH points to last page of memory
movwf   PCLATH   ; where the table sits
movf Value, w              ;  Use the Value as an Offset

;------------- get the real temperature from tale at 0x300 ------------

call CheckFF
call  GetTemp

retlw 0xe2 ;243 -22.550000 -22.5
retlw 0xe2 ;244 -22.650000 -22.5
retlw 0xe2 ;245 -22.750000 -22.5
retlw 0xa3 ;246 -22.850000 -23
retlw 0xa3 ;247 -22.950000 -23
retlw 0xa3 ;248 -23.050000 -23
retlw 0xa3 ;249 -23.150000 -23
retlw 0xa3 ;250 -23.250000 -23
retlw 0xe3 ;251 -23.325000 -23.5
retlw 0xe3 ;252 -23.400000 -23.5
retlw 0xe3 ;253 -23.475000 -23.5
retlw 0xe3 ;254 -23.550000 -23.5

end