;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; ; ; Program: DS18B20 Digital Celsius & Fahrenheit Thermometer ; ; Author: Jake Sutherland ; ; Start Date: Friday 1st July 2011 ; ; Finish Date: ; ; Comments: ; ; ; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; LIST P=PIC16F628A INCLUDE P16F628A.INC __config _CP_OFF & DATA_CP_OFF & _LVP_OFF & _BODEN_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT errorlevel -302 ;Eliminate bank warning ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; ; ; PIC16F628A Microcontroller ; ; ____ ____ ; ; LED 7 Segment 10's CC VREF/AN2/RA2 -| 1 - 18 |- RA1/AN1 LED 7 Segment 1's CC ; ; LED 7 Segment 100's CC CPM1/AN3/RA3 -| 2 17 |- RA0/AN0 LED 7 Segment .1's CC ; ; DS18B20 I/O CMP2/T0CKI/RA4 -| 3 16 |- RA7/OSC1/CLKIN ; ; Fahrenheit/Celsius Select VPP/MCLR/RA5 -| 4 15 |- RA6/OSC2/CLKOUT Temp Format (C/F) Select ; ; VSS -| 5 14 |- VDD ; ; Segment DP INT/RB0 -| 6 13 |- RB7/T1OSC1/ICSPDAT Segment B ; ; Segment C DT/RX/RB1 -| 7 12 |- RB6/T1OSCO/T1CLKI/ICSPCLK Segment A ; ; Segment D CK/TX/RB2 -| 8 11 |- RB5 Segment F ; ; Segment E CCP1/RB3 -|_9____10_|- RB4/PGM Segment G ; ; ; ; ; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; CBLOCK H'20' HUNS ; Jump pointer for Hundreds digit TENS ; Jump pointer for Tens digit ONES ; Jump pointer for Ones digit DECI ; Jump pointer for Decimal digit THOU_COL ; 7 Segment Display Thousands Column, used within ISR HUNS_COL ; 7 Segment Display Hundreds Column, used within ISR TENS_COL ; 7 Segment Display Tens Column, used within ISR ONES_COL ; 7 Segment Display Ones Column, used within ISR COLSEL ; Stores COLUMN SELECT information DIGIT ; Used for Indirect Addressing in Interrupt Service Routine TEMPLO_C ; BS18B20 Celsius Temperature Result Low Byte TEMPHI_C ; BS18B20 Celsius Temperature Result High Byte TEMPLO_F ; Fahrenheit temperature lower byte TEMPHI_F ; Fahrenheit temperature upper byte COUNT ; For counting execution times in various routines SHIFT ; For storing data to shift into and out of the DS18B20 DELAYGPR1 ; Used in delay subroutines FLAGS ; -------0 Temperature Format Select (0 = Celsius 1 = Fahrenheit) ; ------0- Celsius/Fahrenheit Temperature Negative Flag (0 = False 1 = True) ; -----X-- Unused ; ----0--- Positive/Negative Flag after 'Add 4' routine ; ---X---- Unused ; --X----- Unused ; -X------ Unused ; X------- Unused ENDC W_ISR EQU H'70' ; For context saving. Ensures GPR is accessible from any Bank. See Memory Map of 628A S_ISR EQU H'71' ; For context saving. Ensures GPR is accessible from any Bank. See Memory Map of 628A P_ISR EQU H'72' ; For context saving. Ensures GPR is accessible from any Bank. See Memory Map of 628A F_ISR EQU H'73' ; For context saving. Ensures GPR is accessible from any Bank. See Memory Map of 628A ORG H'000' ; Processor reset vector location. On power up, the program jumps here GOTO SETUP ; ORG H'004' ; Interrupt vector location. When an Interrupt occurs, the program jumps here ; (Thanks Mike, K8LH for help with this ISR routine. Contact via Electro-Tech-Online.com) ; Save MOVWF W_ISR ; Save W to W_ISR SWAPF STATUS, W ; Use SWAPF instruction so status bits don't change MOVWF S_ISR ; Save Status to S_ISR CLRF STATUS ; Switch to Bank 0 MOVF PCLATH, W ; Move PCLATH to W register MOVWF P_ISR ; Save PCLATH to P_ISR CLRF PCLATH ; Force page 0 MOVF FSR, W ; Move FSR to W register MOVWF F_ISR ; Save FSR to F_ISR ; Refresh display CLRF PORTB ; Blank the display MOVF PORTA, W ; Move PORTA's current state to W ANDLW B'11100000' ; Clear ONLY Column Select Bits & leave upper nibble unchanged IORWF COLSEL, W ; Inclusive OR above with COLSEL register MOVWF PORTA ; Leave upper nibble of PORTA unchanged & select new column MOVF DIGIT, W ; Column number (DIGIT is initialised to 0. Used for Indirect Addressing) ADDLW THOU_COL ; Add 'DIGIT' to 'THOU_COL' GPR address MOVWF FSR ; FSR = THOU_COL + (0forTHOUS, 1forHUNS, 2forTENS & 3forONES) as they are in sequential order in RAM MOVF INDF, W ; W register now holds the jump pointer for the corresponding digit to be displayed CALL SEGMENT_TABLE ; Get 7 segment arrangement from SEGMENT_TABLE for corresponding digit BTFSC COLSEL, 1 ; Is TENS Column active IORLW B'00000001' ; Yes, so activate TEN's column decimal point MOVWF PORTB ; NO, hide decimal point and display new column ; Prepare for next column interrupt INCF DIGIT, F ; Increment DIGIT jump pointer (used when indirect addressing above) BCF STATUS, C ; Clear C bit of STATUS register RRF COLSEL, F ; Advance column select bit BTFSS STATUS,C ; Was that the last column? (or, Is Carry Flag Set?) GOTO $+D'3' ; NO, do not reset DIGIT and COLumnSELect CLRF DIGIT ; Reset DIGIT jump pointer BSF COLSEL, 3 ; Reset column select to THOU_COL (1XXX) (00001000) ; RESTORE BCF PIR1, TMR2IF ; Clear TMR2 interrupt flag while still in Bank 0 MOVF F_ISR, W ; MOVE F_ISR to W MOVWF FSR ; Restore FSR MOVF P_ISR, W ; MOVE P_ISR to W MOVWF PCLATH ; Restore PCLATH SWAPF S_ISR, W ; Undo previous SWAPF, place result in W MOVWF STATUS ; Restore STATUS SWAPF W_ISR, F ; Use SWAPF instruction so status bits don't change SWAPF W_ISR, W ; Undo previous SWAPF and restore W register RETFIE ; Return From Interrupt ; 7 Segment Display Arrangement Lookup SEGMENT_TABLE ; This routine assigns on/off arrangement to the 7 Segment Display ADDWF PCL, F ; BAFGEDCp JUMP B|A|F|G|E|D|C|p DISPLAY RETLW B'11101110' ; 0 B|A|F|-|E|D|C|- 0 RETLW B'10000010' ; 1 B|-|-|-|-|-|C|- 1 RETLW B'11011100' ; 2 B|A|-|G|E|D|-|- 2 RETLW B'11010110' ; 3 B|A|-|G|-|D|C|- 3 RETLW B'10110010' ; 4 B|-|F|G|-|-|C|- 4 RETLW B'01110110' ; 5 -|A|F|G|-|D|C|- 5 RETLW B'01111110' ; 6 -|A|F|G|E|D|C|- 6 RETLW B'11000010' ; 7 B|A|-|-|-|-|C|- 7 RETLW B'11111110' ; 8 B|A|F|G|E|D|C|- 8 RETLW B'11110110' ; 9 B|A|F|G|-|D|C|- 9 RETLW B'00000000' ; 10 -|-|-|-|-|-|-|- BLANK RETLW B'00010000' ; 11 -|-|-|G|-|-|-|- - RETURN ; Program Originates Here SETUP ; This routine sets up the Microcontroller's Inputs and Outputs MOVLW H'07' ; Turn Comparators off and enable pins for I/O functions MOVWF CMCON ; BSF STATUS, RP0 ; Bank 1 MOVLW B'01110000' ; RA<7><3:0> Output, RA<5:4> Input MOVWF TRISA ; CLRF TRISB ; RB<7:0> Outputs BCF STATUS, RP0 ; Bank 0 CLRF PORTA CLRF PORTB ONE_OFF_INITIALISE ; Clear ALL Bank 0 RAM from 0X20 - 0X7F (96 bytes) BCF STATUS, IRP ; Indirect addressing Bank 0/1 MOVLW H'20' ; Initialise pointer to RAM MOVWF FSR ; (File Select Register) CLRF INDF ; Clear Register indirectly INCF FSR, F ; Increment pointer BTFSS FSR, 7 ; All done? GOTO $-D'3' ; No, Clear next byte ; Initialise Column Select BSF COLSEL, 3 ; Set column select to THOU_COL (1XXX) (00001000) ; Setup TMR2 for 0.0005s or 500uS Interrupts CLRF TMR2 ; Clear TMR2 register BSF STATUS, RP0 ; Bank 1 MOVLW B'00000010' ; 00000010 MOVWF PIE1 ; -------0 Disable TMR1IE - TMR1 Overflow Interrupt Enable bit ; ------1- Enable TMR2IE - TMR2 to PR2 Match Interrupt Enable bit ; -----0-- Disable CCP1IE - CCP1 Interrupt Enable bit ; ----X--- Unused ; ---0---- Disable TXIE - USART Transmit Interrupt Enable bit ; --0----- Disable RCIE - USART Receive Interrupt Enable bit ; -0------ Disable CMIE - Comparator Interrupt Enable bit ; 0------- Disable EEIE - EE Write Complete Interrupt Enable bit BCF STATUS, RP0 ; Bank 0 CLRF PIR1 ; Clear Peripheral Interrupt Flags MOVLW B'00000001' ; 00000001 MOVWF T2CON ; ------01 Pre-scale 1:4 ; -----0-- TMR2 OFF ; -0000--- Post-scale 1:1 ; 0------- Unused BSF STATUS, RP0 ; Bank 1 MOVLW D'250' ; MOVWF PR2 ; Interrupt every 0.001s or 1mS BCF STATUS, RP0 ; Bank 0 BSF INTCON, GIE ; Enable Global Interrupts BSF INTCON, PEIE ; Enable Peripheral Interrupts BSF T2CON, TMR2ON ; Start TMR2 GOTO GET_TEMP ; Dallas DS18B20 Temperature Sensor 'One Wire' Communication Routines DS18B20_RESET ; This routine Resets the DS18B20 CALL DQ_LL ; Force the DQ Line to Logic Low MOVLW (D'480'-D'5')/D'5' ; Reset pulse must be held a minimum of 480uS. CALL DELAY ; For delays from 10uS to 1285uS. Example, MOVLW D'10' for 10uS, MOVLW D'500' for 500uS. (D'n'-D'5')/D'5'; n must be divisible by 5 CALL DQ_HIZ ; Release DQ Line MOVLW (D'60'-D'5')/D'5' ; Wait for recovery CALL DELAY ; BTFSC PORTA, 4 ; Test for 'Presence Pulse' GOTO DS18B20_RESET ; If not present, Reset MOVLW (D'420'-D'5')/D'5' ; Must wait a minimum of 480uS from when DQ line is released before moving on CALL DELAY ; RETURN ; DS18B20_READ_BYTE ; This routine reads a byte of data from the DS18B20 MOVLW H'08' ; Amount of bits to shift out MOVWF COUNT ; Store in COUNT GPR CALL DS18B20_READ_BIT ; Read bit RRF SHIFT, F ; Rotate bit out of carry into SHIFT GPR DECFSZ COUNT, F ; Decrement COUNT GOTO $-D'3' ; If not zero, read next bit MOVF SHIFT, W ; If zero, move SHIFT GPR to W RETURN ; DS18B20_READ_BIT ; This routine reads one bit of data from the DS18B20 BCF INTCON, GIE ; Disable Global Interrupts CALL DQ_LL ; Force the DQ Line to Logic Low CALL DQ_HIZ ; Release DQ Line BSF STATUS, C ; Pre-set Carry Flag BTFSS PORTA, 4 ; Test DQ Line BCF STATUS, C ; If zero, Clear Carry Flag BSF INTCON, GIE ; Enable Global Interrupts MOVLW (D'60'-D'5')/D'5' ; Wait for Time Slot to end CALL DELAY ; RETURN ; DS18B20_WRITE_BYTE ; This routine writes a byte of data to the DS18B20 MOVWF SHIFT ; Move data to shift into DS18B20 to SHIFT GPR MOVLW D'08' ; Amount of bits to shift in MOVWF COUNT ; Store in COUNT GPR RRF SHIFT, F ; Rotate valid data into Carry Flag CALL DS18B20_WRITE_BIT ; Write bit DECFSZ COUNT, F ; Decrement COUNT GOTO $-D'3' ; If not zero, read next bit RETURN ; If zero, RETURN DS18B20_WRITE_BIT ; This routine writes one bit of data to the DS18B20 BCF INTCON, GIE ; Disable Global Interrupts CALL DQ_LL ; Force the DQ Line to Logic Low BTFSS STATUS, C ; Test Carry Flag GOTO $+D'2' ; If zero, leave DQ Line Logic Low CALL DQ_HIZ ; If not zero, release DQ Line to Logic High MOVLW (D'60'-D'5')/D'5' ; Hold Logic Low, write 0 CALL DELAY ; CALL DQ_HIZ ; If not zero, release DQ Line to Logic High, write 1 BSF INTCON, GIE ; Enable Global Interrupts RETURN ; DQ_HIZ ; This routine forces the DQ Line to an Input / High Impedance state BSF STATUS, RP0 ; Bank 1 BSF TRISA, 4 ; Make Pin 3 an input, Pull-up resistor forces line to logic 1, unless DS18B20 pulls it low BCF STATUS, RP0 ; Bank 0 RETURN DQ_LL ; This routine forces the DQ Line to Logic Low BCF PORTA, 4 ; Clear output latch BSF STATUS, RP0 ; Bank 1 BCF TRISA, 4 ; Make Pin 3 an output BCF STATUS, RP0 ; Bank 0 RETURN DELAY ; This routine can provide delays from 10uS to 1285uS depending on the number moved to the Working register prior to calling the delay MOVWF DELAYGPR1 ; Move integer to GPR NOP ; No Operation NOP ; No Operation DECFSZ DELAYGPR1, F ; Decrement GPR and place back in itself GOTO $-D'3' ; Not finished, GOTO here - 3 instructions RETURN ; Finished, Return GET_TEMP CALL DS18B20_RESET ; Reset MOVLW H'CC' ; Skiprom CALL DS18B20_WRITE_BYTE ; Skiprom MOVLW H'44' ; Convert T CALL DS18B20_WRITE_BYTE ; Convert T CALL DS18B20_READ_BIT ; Initiate Read Time Slots BTFSS STATUS, C ; DS18B20 transmits a 0 while the temperature conversion is in progress and a 1 when the conversion is done GOTO $-D'2' ; Transmitting 0 therefore NOT done CALL DS18B20_RESET ; Reset MOVLW H'CC' ; Skiprom CALL DS18B20_WRITE_BYTE ; Skiprom MOVLW H'BE' ; Read Scratchpad CALL DS18B20_WRITE_BYTE ; Read Scratchpad CALL DS18B20_READ_BYTE ; Move Scrachpad Byte 0 to W MOVWF TEMPLO_C ; Store in Celsius TEMPLO GPR CALL DS18B20_READ_BYTE ; Move Scrachpad Byte 1 to W MOVWF TEMPHI_C ; Store in Celsius TEMPHI GPR ; Test Temperature Format Select pin and display corresponding temperature type (C or F) BTFSS PORTA, 5 ; Test Select pin for high or low GOTO DISPLAY_CELSIUS ; Clear, display Celsius ; Set, display Fahrenheit ; Begin converting 16 bit Celsius data into Fahrenheit DISPLAY_FAHRENHEIT ; This routine Clear all Flags and copies Celsius data into Fahrenheit GPRs for conversion CLRF FLAGS ; Clear Flags GPR MOVF TEMPLO_C, W ; Copy Celsius Temperature Data lower byte MOVWF TEMPLO_F ; Move to Fahrenheit GPR lower byte MOVF TEMPHI_C, W ; Copy Celsius Temperature Data upper byte MOVWF TEMPHI_F ; Move to Fahrenheit GPR upper byte ; The following group of routines convert the Celsius Temperature Data into Fahrenheit x 10. ; This is acheived by dividing by 8 and adding the original number, which gives 18 times the value. ; If you now add 320 you will have the temperature in Fahrenheit x 10. ; After the conversion it is simply a matter of displaying the data with the decimal shifted one place to the right. ; Example ; 25 Degrees C = B'00000001 10010000' = D'400' ; 400 / 8 = 50 ; 50 + 400 = 450 ; 450 + 320 = 770 ; 770 / 10 = 77 Degrees Fahrenheit ; Add 4, this ensures number is correctly rounded when using the shift method below to divide MOVLW B'00000100' ; Move D'4' to W ADDWF TEMPLO_F, F ; Add W to TEMPLO_F and place result back in File Register TEMPLO_F BTFSC STATUS, C ; Check if TEMPLO_F overflowed INCF TEMPHI_F, F ; Overflow occurred, increment upper register ; Flag if result positive or negative after add 4 (needed for mask routine) BTFSC TEMPHI_F, 7 ; Test bit 7 of TEMPHI_F BSF FLAGS, 3 ; Set flag if negative, skip if clear ; Divide by 8 using shift method RRF TEMPHI_F, F ; Rotate Right File Register 'F' (TEMPHI_F) into carry RRF TEMPLO_F, F ; Rotate Right File Register 'F' (TEMPLO_F) out of carry; / 2 RRF TEMPHI_F, F ; Repeat... RRF TEMPLO_F, F ; / 4 RRF TEMPHI_F, F ; RRF TEMPLO_F, F ; / 8 ; Mask routine. Adjust upper 3 bits of TEMPHI_F due to shift. Set if negative, clear if positive BTFSS FLAGS, 3 ; Test if result after 'Add 4' is positive or negative GOTO $+D'4' ; Positive, GOTO here + D'4' MOVLW B'11100000' ; Negative, IORWF TEMPHI_F, F ; Set upper 3 bits GOTO $+D'3' ; Done, Skip MOVLW B'00011111' ; Positive, ANDWF TEMPHI_F, F ; Clear upper 3 bits ; Add original Celsius Temperature to obtain C x 18 MOVF TEMPLO_C, W ; Move TEMPLO_C to W ADDWF TEMPLO_F, F ; Add TEMPLO_C and TEMPLO_F and place result back in File Register TEMPLO_F MOVF TEMPHI_C, W ; Pre-load TEMPHI_C to W (doesn't effect carry) BTFSC STATUS, C ; Did Add cause overflow? INCF TEMPHI_C, W ; Yes, increment TEMPHI_C store in W ADDWF TEMPHI_F, F ; Add TEMPHI_C and TEMPHI_F. Result in now C x 18 ; Add 320 to obtain F x 10 MOVLW B'01000000' ; 320 lower byte ADDWF TEMPLO_F, F ; Add 320 lower byte and TEMPLO_F and place result back in File Register TEMPLO_F BTFSC STATUS, C ; Did Add cause overflow? INCF TEMPHI_F, F ; Yes, increment TEMPHI_F MOVLW B'00000001' ; 320 upper byte ADDWF TEMPHI_F, F ; Add 320 upper byte and TEMPHI_F. Result is now C x 18 + 320 (= F x 10) BTFSS TEMPHI_F, 7 ; Test Sign Bits for Fahrenheit Temperature negative (2's complemented) GOTO BIN_TO_DEC_F ; No, skip undo 2's complement COMF TEMPLO_F, F ; Invert TEMPLO COMF TEMPHI_F, F ; Invert TEMPHI INCFSZ TEMPLO_F, F ; Increment TEMPLO once; After inverting the data, add one to achieve equivalent positive number (see 2's complement) GOTO $+D'2' ; No overflow skip next instruction INCF TEMPHI_F, F ; Overflow occurred, increment upper byte BSF FLAGS, 1 ; Set Negative Flag for Fahrenheit Temperature BIN_TO_DEC_F ; This routine converts a 16-bit number held in TEMPHI_F:TEMPLO_F to Decimal and stores it in 4 GPR's; HUNS, TENS, ONES & DECI ; !!!!! Tweaked for this program due to Fahrenheit x 10. GPR Labels adjusted for this program and would normally be THOUS, HUNS, TENS & ONES instead of HUNS, TENS, ONES & DECI !!!!! ; Example 1225; ; THOUS holds amount of thousands (i.e. 0000 0001 = 1x1000) ; HUNS holds amount of hundreds (i.e. 0000 0010 = 2x100) ; TENS holds amount of tens (i.e. 0000 0010 = 2x10) ; ONES holds amount of ones (i.e. 0000 0101 = 5x1) ; These registers are then used as jump pointers when calling digits to display INCF TEMPLO_F ; Pre-load TEMPHI + 1 INCF TEMPHI_F ; Pre-load TEMPHI + 1 CLRF HUNS ; THOUS = 0000 0000 GPR changed from THOUS for this program MOVLW D'246' ; Move decimal '246' to W MOVWF TENS ; HUNS GPR = 1111 0101 GPR changed from HUNS for this program MOVWF ONES ; TENS GPR = 1111 0101 GPR changed from TENS for this program MOVWF DECI ; ONES GPR = 1111 0101 GPR changed from ONES for this program DECFSZ TEMPLO_F, F ; Decrement TEMPLO_F register GOTO $+D'4' ; Not 0, GOTO here + 4 instructions DECFSZ TEMPHI_F, F ; Decrement TEMPHI_F register GOTO $+D'2' ; Not 0, skip next instruction GOTO $+D'9' ; Is 0, done, GOTO here + 9 instructions INCFSZ DECI, F ; Increment ONES register, skip if 0 GPR changed from ONES for this program GOTO $-D'6' ; Not 0, GOTO here - 6 instructions INCFSZ ONES, F ; Is 0, Increment TENS register skip if 0 GPR changed from TENS for this program GOTO $-D'9' ; Not 0, GOTO here - 9 instructions & reset the ONES register to D'246' INCFSZ TENS, F ; TENS overflowed, Increment HUNS skip if 0 GPR changed from HUNS for this program GOTO $-D'12' ; Not 0, GOTO here - 12 instructions & reset the ONES and TENS registers to D'246' INCF HUNS, F ; HUNS overflowed, Increment THOUS GPR changed from THOUS for this program GOTO $-D'15' ; GOTO here - 15 instructions & reset the ONES, TENS & HUNS registers to D'246' SUBWF TENS, F ; W still holds D'246 so subtract it from HUNS register to determine how many 'HUNS' (0-9) GPR changed from HUNS for this program SUBWF ONES, F ; W still holds D'246 so subtract it from TENS register to determine how many 'TENS' (0-9) GPR changed from TENS for this program SUBWF DECI, F ; W still holds D'246 so subtract it from ONES register to determine how many 'ONES' (0-9) GPR changed from ONES for this program GOTO ZERO_SUPPRESS_AND_NEG_SIGN DISPLAY_CELSIUS BCF FLAGS, 1 ; Clear Negative Flag BTFSS TEMPHI_C, 7 ; Test if Temperature is negative (2's complement format) GOTO REARRANGE_DATA ; NOT Negative, skip 'Undo 2's Complement' BSF FLAGS, 1 ; Set Negative Flag; used later ; Undo 2's Complement. When the Temperature is Negative, the DS18B20 outputs the 2's Complement. This routine converts the negative data into its positive equivalent ; Example Negative Temperature TEMPHI = 1111 1110 TEMPLO = 0110 1110 = -25.1250 (see datasheet) COMF TEMPLO_C, F ; Invert TEMPLO COMF TEMPHI_C, F ; Invert TEMPHI INCFSZ TEMPLO_C, F ; Increment TEMPLO once; After inverting the data, add one to achieve equivalent positive number (see 2's complement) GOTO $+D'2' ; No overflow skip next instruction INCF TEMPHI_C, F ; Overflow occurred, increment upper byte ; Example Negative Temperature AFTER undo TEMPHI = 0000 0001 TEMPLO = 1001 0010 = +25.1250 REARRANGE_DATA ; This routine rearranges the 2 Temperature result bytes into usable data. ; EXPLANATION: ; * After the DS18B20 finishes a Temperature Conversion, the 12-bit result is stored in two 8-bit ; registers as a 16-bit sign-extended two?s complement number. ; * The 5 MSb's of the MSB (TEMPHI_C) indicate a negative or positive temperature. ; * The output data follows this format (12-bit resolution; 0.0625 degrees Celsius increments); ; ; SSSS SNNN : NNNN FFFF Where S = Sign (0 = Positive 1 = Negative) ; N = Number, & ; F = Fraction (16 X 0.0625 increments = 1) ; ; After communication with the DS18B20 the output data is held in two 8 bit registers called ; TEMPHI_C & TEMPLO_C in the following format TEMPHI_C = SSSS SNNN : TEMPLO_C = NNNN FFFF ; ; Example; 0000 0011 1001 0001 = (D'913' X 0.0625) = 57.0625 Degrees Celsius ; ; * This 6 instruction routine below rearranges the 4 nibbles of TEMPHI_C & TEMPLO_C so the data ; is easy to work with. ; * The MSB (TEMPHI_C) will be used for the 'whole' number i.e. 1's, 10's & 100's digits (57); ; and the LSB (TEMPLO_C) will be used for the decimal digit (.1's) with the upper nibble of the ; LSB masked. (These are in fact the sign bits, but we have already handled negative data and ; created a Flag (FLAGS, 1) for negative temperatures. ; ; Example above, after rearrangement 0011 1001 0000 0001 (see below) ; ; Example before; TEMPHI_C = 0000 0011 TEMPLO_C = 1001 0001 = 57.0625 Degrees Celsius MOVLW B'11110000' ; W = 1111 0000 ANDWF TEMPLO_C, W ; F = 1001 0001 W = 1001 0000 IORWF TEMPHI_C, F ; F = 0000 0011 F = 1001 0011 SWAPF TEMPHI_C, F ; F = 1001 0011 F = 0011 1001 (New TEMPHI_C) MOVLW B'00001111' ; W = 0000 1111 ANDWF TEMPLO_C, F ; F = 1001 0001 F = 0000 0001 (New TEMPLO_C) ; Example after; TEMPHI_C = 0011 1001 TEMPLO_C = 0000 0001 ; = D'57' (X 1.0) = 57 = D'1' (X 0.0625) = 0.0625 = 57.0625 Degrees Celsius BIN_TO_DEC_C ; This routine converts the 8-bit number held in TEMPHI_C to Decimal and stores it in 3 GPR's; HUNS, TENS & ONES ; Example 225; ; HUNS holds amount of hundreds (i.e. 0000 0010 = 2x100) ; TENS holds amount of tens (i.e. 0000 0010 = 2x10) ; ONES holds amount of ones (i.e. 0000 0101 = 5x1) ; These registers are then used as jump pointers when calling digits to display INCF TEMPHI_C ; Pre-load TEMPHI + 1 CLRF HUNS ; HUNS = 0000 0000 MOVLW D'246' ; MOVE Decimal'246' to W MOVWF TENS ; TENS GPR = 1111 0101 MOVWF ONES ; ONES GPR = 1111 0101 DECFSZ TEMPHI_C, F ; Decrement TEMPHI register GOTO $+D'2' ; NOT 0, skip next instruction GOTO $+D'7' ; IS 0, TEMPHI = 0000 0000, skip next 6 instructions and calculate how many tens and hundreds INCFSZ ONES, F ; Increment ONES register, skip if 0 GOTO $-D'4' ; NOT 0, GOTO here - 4 instructions INCFSZ TENS, F ; IS 0, Increment TENS register skip if 0 GOTO $-D'7' ; GOTO here - 7 instructions & reset the ONES register to D'246' INCF HUNS, F ; TENS overflowed, Increment HUNS GOTO $-D'10' ; GOTO here - 10 instructions & reset the ONES and TENS registers to D'246' SUBWF TENS, F ; W still holds D'246 so subtract it from TENS register to determine how many 'TENS' SUBWF ONES, F ; W still holds D'246 so subtract it from ONES register to determine how many 'ONES' FRACTION_ROUND ; This routine rounds the fraction portion of the Temperature data to the nearest .1 ; Provided by & used with his permission from 'Pommy'. Contact via Electro-Tech-Online.com ; Examples ; TENTHS = Fraction * 10 / 16 ; TENTHS = 00000100 ( D'4' * 0.0625 = 0.2500 Degrees C) * 10 / 16 = 3 ; TENTHS = 00001001 ( D'9' * 0.0625 = 0.5625 Degrees C) * 10 / 16 = 6 ; TENTHS = 00001101 (D'13' * 0.0625 = 0.8125 Degrees C) * 10 / 16 = 8 MOVLW B'00001111' ; ANDWF TEMPLO_C, F ; MOVF TEMPLO_C, W ; ADDWF TEMPLO_C, F ; *2, C=0 RLF TEMPLO_C, F ; *4, C=0 ADDWF TEMPLO_C, F ; *5, C=0 RLF TEMPLO_C, F ; *10 MOVLW B'00001000' ; ADDWF TEMPLO_C, F ; Rounding SWAPF TEMPLO_C, W ; Pseudo divide by 16 ANDLW B'00001111' ; MOVWF DECI ; ZERO_SUPPRESS_AND_NEG_SIGN ; Leading zero suppression & minus (-) sign if Temperature Negative MOVF HUNS, W ; MOVF instruction affects Z bit of STATUS register BTFSC STATUS, Z ; Does HUNS = 0? MOVLW B'00001010' ; Yes, jump Pointer for blank arrangement BTFSC FLAGS, 1 ; Is Temperature Negative? MOVLW B'00001011' ; Yes, jump Pointer for '-' arrangement MOVWF HUNS ; BTFSS STATUS, Z ; Does HUNS = not 0? GOTO $+D'5' ; Yes, do not blank TENS MOVF TENS, W ; MOVF instruction affects Z bit of STATUS register BTFSC STATUS, Z ; Does TENS = 0? MOVLW B'00001010' ; Yes, jump Pointer for blank arrangement MOVWF TENS ; ; This routine would not be needed if interrupts were disabled for the whole BIN_TO_DEC routine. So this is added to minimise the amount of time interrupts are disabled to minimise flicker. BCF INTCON, GIE ; Disable Interrupts MOVF HUNS, W MOVWF THOU_COL MOVF TENS, W MOVWF HUNS_COL MOVF ONES, W MOVWF TENS_COL MOVF DECI, W MOVWF ONES_COL BSF INTCON, GIE ; Enable Interrupts GOTO GET_TEMP END ; Directive 'end of program'