Digital thermomether report

Course Number

ELN - 232

Course Title

Introduction to Microprocessors

REPORT TITLE Digital Thermometer

Section

5

NUMBER Final Project

Semester Spring Year 2014 Date Performed

May 1

Instructor

Dennis Leak

Student Name

Ramon Martinez

Grade________

Date Submitted

May 7

Lab Instructor Dennis Leak

English and Spelling:____/25

Format:____/25

Content:____/50

Number of Misspelled words________

May7, 2014 ELN232-05 Ramon Martinez Lab Report Final Digital Thermometer

1.- Purpose To design and build a digital thermometer that would measure temperature and display results in fahrenheit and celsius degrees, with adjustable threshold temperature.

2.- Parts List: Parts

Designator

Quantity

Value

Microcontroller

U1

1

PIC16F87A

Voltage Regulator

U2

1

LM7805Z - 5V

LED Display

U3

1

4 digit 7 segment

Temperature Sensor

U4

1

LM335Z

Voltage Reference

U5

1

LM4040AIZ

Resistor

R1

1

330Ω

Resistor

R2,R6,R7,R8,R9,R11

6

2.2kΩ

Resistor

R3

1

4.7kΩ

Resistor

R4

1

3.9kΩ

Resistor

R5

1

2x8 DIP 330Ω

Resistor

R10

1

910Ω

Resistor

R12,R13

2

1kΩ

Transistor

Q1,Q2,Q3,Q4

4

2N3906

Capacitor

C1

1

0.1µF

Capacitor

C2

1

Tantalum 4.7µF

Capacitor

C3,C5

2

0.01µF

Capacitor

C4

1

33pF

Capacitor

C6

1

4.7µF

Capacitor

C7

1

47µF

Push Button

PB1

1

Tact Switch

Slide Switch

S1

1

SPDT

DC Plug

J1

1

Jack, DC Power

LED

LED1

1

Green LED

Table 1: Parts List

3.- Equipment List Equipment

Manufacturer

Model

Description

Hp 34401A Multimeter

Hewlett Packard

34401A

Digital Multimeter (DMM)

Breadboard

Jameco

WBU-208-R

7.3 x 7.5 3220 PNTS Breadboard

Programmer

Microchip

PickIt2

Programmer and Debugger

Oscilloscope

Sun Equipment Corp.

OS-221005

100 Mhz Oscilloscope

Table 2: Equipment List

4.- The Project A digital thermometer is a good project for this introductory course because it provides an opportunity to learn using sensors to measure analogic signals and how to make them interact to the microcontroller so it can produce an output understandable by humans.

The project is based on a PIC16F876A microcontroller, a LM335Z temperature sensor and a LM4040AIZ voltage reference. The LM335Z is an analog sensor that converts the detected temperature to a proportional analog voltage, it produces an electrical output proportional to the temperature in Celsius. The output from the sensor is connected to one of the ADC channel inputs of the PIC16F876A microcontroller to obtain the equivalent temperature value in digital format, and then show it on the 4 digit 7 segment LED display.

Since the experiment required the results to be in the Fahrenhet scale also, an artihmetic calculation has to be performed by means of addition and substraction to obtain such results.

The switching function between Celsius values and Fahrenheit values is provided by a slide switch.

A look-up table which reads the adc results and returns a set of display values used in this experiment.

The down side of this approach is that it takes a lot of room.

Flow Chart

START

THERMOMETER

RETURN

FLOWCHART

SET ALL PORTS SET ADCON

DELAY

INITIALIZE

ADCON0

CONVERT TO PD

MAIN

ANALOG CONVERSION

ADC RESULTS

INCREMENT OR DECREMENT

CALCULATION RESULTS

CONVERT ADC

CELSIUS OR FAHRENHEIT CALCULATION

INITIAL VARIABLE

CELSIUS OR FAHRENHEIT THRESHOLD

THRESHOLD RESULTS

ADC CONVERSION

RETURN

SAVE RESULTS

DELAY

RETURN

SAVE RESULTS

RETURN

Block Diagram

THERMOMETER BLOCK DIAGRAM

THE DIAGRAM SHOWS THE MAJOR COMPONENTS OF A THERMOMETER CONTROLLED BY A PIC16F876A MICROPROCESSOR.

PIC 16F876A MICROCONTROLLLER

LED TO SHOW WHEN THRESHOLD HAS BEEN REACHED

TWO POSITION SWITCH TO CHANGE FROM FAHRENHEIT TO CELSIUS

7 SEGMENT 4 DIGIT DISPLAY TO SHOW TEMPERATURE READINGS

IT INCLUDES THE +5V VOLTAGE SOURCE, PUSH BUTTONS FOR THRESHOLD ADJUSTMENT, RC OSCILLATOR NETWORK, TEMPERATURE SENSOR, VOLTAGE REFERENCE, SWITCH TO GO FROM FAHRENHEIT TO CELSIUS DEGREES, SEVEN SEGMENT 4 DIGITS DISPLAY (ONLY THREE ARE USED) TO DISPLAY RESULTS AND AN LED TO SHOW WHEN THRESHOLD TEMPERATURE HAS BEEN REACHED.

+5V VOLTAGE FROM ICSP TO DRIVE THE MICROCONTROLLER PUSH BUTTONS TO ADJUST TEMPERATURE THRESHOLD

RC OSCILLATOR

LM335Z TEMPERATURE SENSOR

LM4040AIZ VOLTAGE REFERENCE IC

Parts List

Thermometer parts list with cost Quantity

Description

Provider

Cost per unit

Total

1

Microchip PIC16F876A

Jameco Electronics

$4.49

$4.49

1

DIL 330 x 8 Resistor Array

ABRA Electronics Canada

$1.80

$1.80

1

4DIGIT 7Segment Green CA 12-Pin PDIP

Jameco Electronics

$1.75

$1.75

4

2N3906 BJT Transistor

Jameco Electronics

$0.06

$0.24

6

Resistor Carbon Film 2.2k Ohm 1/4 Watt 5%

Jameco Electronics

$0.09

$0.54

1

Resistor Carbon Film 330 Ohm 1/4 Watt 5%

Jameco Electronics

$0.09

$0.09

1

Resistor Carbon Film 4.7k Ohm 1/4 Watt 5%

Jameco Electronics

$0.09

$0.09

1

Resistor Carbon Film 3.9k Ohm 1/4 Watt 5%

Jameco Electronics

$0.09

$0.09

2

Resistor Carbon Film 1k Ohm 1/4 Watt 5%

Jameco Electronics

$0.09

$0.18

1

Resistor Carbon Film 910 Ohm 1/4 Watt 5%

Jameco Electronics

$0.09

$0.09

1

Switch Slide Min Single Pole Double Throw On-On PCB Mount Jameco Electronics

$0.39

$0.39

2

.01 uF 50 Volt Ceramic Disc Capacitor

Jameco Electronics

$0.09

$0.18

1

0.1 uF 50 Volt Ceramic Disc Capacitor

Jameco Electronics

$0.09

$0.09

1

33 pF 50 Volt Ceramic Disc Capacitor

Jameco Electronics

$0.09

$0.09

1

4.7uF 35 VOLT TANTALUM CAPACITOR

Jameco Electronics

$0.49

$0.49

1

47 uF 50 Volt Radial Capacitor

Jameco Electronics

$0.09

$0.09

1

4.7 uF 50 Volt Radial Capacitor

Jameco Electronics

$0.10

$0.10

1

IM206 6x6x6mm Tact Switch

Microtivity

$0.50

$0.50

1

LM35Z Temperature Sensor Analog Serial3 Pin TO-92 Box

Jameco Electronics

$0.49

$0.49

1

LM4040 Voltage Reference Precision 5 Volt 15 mA 3-Pin TO-92 Jameco Electronics

$1.35

$1.35

1

LED Uni-Color Green 565nm 2-Pin

Jameco Electronics

$0.15

$0.15

1

LM7805CT Standard Regulator 5 Volt 1 Amp 3 Pin

Jameco Electronics

$0.45

$0.45

1

JACK,DC POWER,MALE

Jameco Electronics

$0.45

$0.45

Total

$14.18

1

PICkit 2 Starter Kit Microcontroller Programmer and Debugger

Jameco Electronics

$79.95

$79.95

1

3220-Point Solderless Breadboard 7.3"Lx7.5"W

Jameco Electronics

$36.95

$36.95

Total Including opional items

Jameco Electronics 1355 Shoreway Road Belmont, CA 94002 Phone: 1-800-831-4242 Fax: 1-800-237-6948 Email: Sales@Jameco.com

!!

ABRA Electronics Canada 1-800-361-5237 www.abra-electronics.com

!!

Amazon.com 1200 12th Ave. S., Suite 1200 Seattle, WA 98144

$131.08

5.- Conclusion The Digital thermometer was built using a 3220 Points solderless breadboard. After placing the PIC16F876A on it, it was connected to a push button through a 2,2k resistor on pin 1 and through a 0.1µF capacitor to ground, to set the Rest circuit.

After this was done, the LM335Z temperature sensor which was connected to AN0 (pin2) trhough a 1kΩ resistor. To this same terminal, the +5V signal was connected through a 2.2kΩ resistor, finallly the third terminal was grounded.

Third step required connecting the voltage reference LM4040AIZ to the pic using AN3 (pin5), through a 910Ω and a 1kΩ in parallel wich in turn connected to Vdd (pin20) and pin #2 of the ICSP.

The 6 pins of the programmer were connected as follows: Pin1 to MCLR of the Pic (pin1).

Pin2 to a green LED through a 330Ω resistor; throuygh a 4.7kΩ resistor to the reset circuit 9pin1 on the Pic); finally to Vss2 (pin20 on the pic) through a 0.1µF ceramic capacitor.

Pin3 was grounded.

Pin4 to RB7 (pin 28 on the Pic) Pin5 to RB5 9pin27 on the Pic) Pin6 was not connected.

Since he ADC circuit reading can be affected due to the fact that all the system is pulling off the same +5V source, capacitors are placed by each analog input to smooth out dips and surges in the current caused by the other components.

The PIC 16F876A Microcontroller offers 10 Bit Analog to Digital Conversion. When it measures an incoming voltage, it compares that voltage to a reference voltage, and produces the comparison as a 10-bit number. This result is then translated into a Celsius degree value to be displayed on the LED display.

A slide switch was installed to RB5 (pin26) to provide the function of switching from Fahrenheit to Celsius degrees and viceversa.

A 4.7µF Tantallum capacitor was connected through AN3 (pin5) and ground.

The RC network, which provides the clock for the Microcontroller was composed of a 3.9kΩ resistor in series with a 33pF capacitor connected to CLK1 (pin9).

To provide stable external power to the circuit after it is unplugged from the programmer, a LM7805 voltage regulator was connected to Vdd using two capacitors, a 47µF to line voltage and a 4.7µF to the terminal that connects to the circuit, a Jack DC plug was used to drive the power from the external source, a 12VDC transformer.

Finally a 4 digit 7 segment LED display was placed in the circuit through a 330Ω resistor array, and 4 2N3906 transistors were used to light up the LEDS. This transistors were connected to the PIC through 4 2.2kΩ resistors and all the emitter legs to a 0.01µF capacitor.

All the circuit is shown as it was built on the schematics included in this report.

Main Code

;*********************************************************************** ; File Name: Main.asm ; Description: A Main program that calls other device drivers. ; ; ; Written by: RAMON MARTINEZ ; Build with: MPASM ; Processor: PIC16F876A ; Change history: ; 0.1 2011/10/02 DDL Initial version ; ;*********************************************************************** ; Pins Used: ; Oscillator is R-C network = 3.9k and 33pf => ~ 4MHz ; Port A: Being Used. ; Port B: Select bits 0-3 for the 4 digits, 0 being the right most digit ; Port C: 7-0 set as output ; Port D: Not defined for this PIC ; Port E: Not defined for this PIC ; ; *************************************************************************** #include <p16F876a.inc> #include <PIC16Macros.asm>

__CONFIG _LVP_OFF & _CPD_OFF & _CP_OFF & _PWRTE_ON & _WDT_OFF & _WRT_OFF & _RC_OSC ; Declarations:

cblock 0x20

W_temp

STATUS_temp

Digit:4

DelayCnt

DelayMs

KeyHold

ScanCount Flags: endc

local Temperature

;============= ; Program Start:

org 0

goto Start

org 4

goto ISR

; Place for W reg in the Interrupt Service Rout. (ISR) ; Place to hold the Status in the ISR ; define a variable to hold the 0-4 char of LED display ; define a variable to hold DelayCnt ; define a variable to hold DelayMs ; Temporary holding place for a key ; Place for counting the scans

; Declare that temperature is in AnalogDriver.asm

; Declare to the Assembler that this code starts at 0 ; Jump to the Start routine ; Declare to the Assembler that this code starts at 4 ; Jump to the ISR code

Start:

Main: Loop:

call

Initialize

decf ScanCount,F btfss STATUS,Z goto NoADC movlw .100 movwf ScanCount movlw 0 call Temperature1 call Thermo

NoADC:

call LED_Scan

movlw .4 call Delay

goto Loop nop nop

goto $+0

; See if we have exhaused the scan count ; Jump over the A/D conversion ; Set back up the scan count ; Only do ADC every .5 second (scan is 5ms) ; Set w to 0 for channel 0

; Scan the LED display ; Delay to allow LED Display Scan to be viewed

; Loop here forever

;SegmentLookUp uses a table lookup approach. Call this routine with ; binary data in the W reg where it will be translated to the scan code. This routine must be in the first ;100 bytes of the first program page. Input: W reg contains Digit 0-15, to be translated. ; Output: Translated data in W reg SegmentLookUp: clrf PCLATH

addwf PCL,F

retlw 0x3f

retlw 0x06

retlw 0x5B

retlw 0x4F

retlw 0x66

retlw 0x6D

retlw 0x7D

retlw 0x07

retlw 0x7F

retlw 0x6F

retlw 0x77

retlw 0x7C

retlw 0xB9

retlw 0x5E

retlw 0x79

retlw 0xF1

;decode 0 ;decode 1 ;decode 2 ;decode 3 ;decode 4 ;decode 5 ;decode 6 ;decode 7 ;decode 8 ;decode 9 ;decode A ;decode B ;decode C ;decode D ;decode E ;decode F

#include <PicLEDDsplyDriver.asm> #include <AnalogDriver.asm> ;#include <PicToneDriver.asm> ;============= ; Subroutines: ; Initialize Function. This initialize routine will set up all the ports, ; timer, analog and comparator functions. ; Inputs: none ; Outputs: none Initialize:

; Initialize port data registers

; Binary used to see individual pin level

bcf STATUS,RP1 ; set to RAM page 0

bcf STATUS,RP0 ; set to RAM page 0

movlw b’00000000’ ; all port pins = low

movwf PORTA

movlw b’11111111’ ; Set to select digit0 (active = 0)

movwf PORTB

movlw b’11111111’ ; Set all segments to high (off )

movwf PORTC

movlw b’11111111’ ; Fosc/8; channel 0; ADC on movwf ADCON0 ;

bsf STATUS,RP0 ; set RAM Page 1 for TRIS registers

movlw b’10000101’ ; RA5,4,2=digital; AN3=+Vref; AN1,AN0=analog

movwf ADCON1 ; Set bit 7=Right Justify A/D out.

movlw b’11011111’ ; RA5=output;RA4,2=inputs

movwf TRISA

movlw b’11110000’

movwf TRISB

movlw b’00000000’ ; except port C we want as all outputs

movwf TRISC

bcf STATUS,RP0 ; back to RAM page 0 clrf Digit clrf Digit+1 clrf Digit+2 clrf Digit+3 clrf CelsiusPD clrf CelsiusPD+1 return

; ISR Function. This Interrupt Service Routine (ISR) will do all the things ; necessary to service the interrupt. ; INPUTS: none ; OUTPUTS: none

ISR:

movwf

movf

movwf

movf

movwf

swapf

swapf retfie

W_temp STATUS,w STATUS_temp STATUS_temp,w STATUS W_temp,f W_temp,w

; Stores W reg in temp register ; Stores STATUS in temp ; register ; Restore STATUS register to the ; original value ; Restores W reg to original value, ; does not affect the STATUS!

; Delay Function. Enter with number of 1mSec delays in Wreg ; INPUTS: Wreg contains number of 1 millisecond delays ; OUTPUTS: none Delay:

movwf DelayMs ; this timing relies on the speed of the processor

movlw .71 ; delay ~1000uS

movwf DelayCnt

decfsz DelayCnt,f ; this loop does 215 cycles

goto $-1

decfsz DelayCnt,f ; This loop does 786 cycles

goto $-1

decfsz DelayMs,f ; Delay the outerloop the number of milliseconds

goto $-7 return

; This is the end of all the program code end

Analog Driver Code

;**************************************************************************** ; File Name: AnalogDriver.asm ; Title: “Digitize the Analog” ; ; Function: This assembly code will provide the Analog code ; to convert the analog voltage, appearing on the ; analog pins, to a digital value. ; ; Developed using MPLAB version 8.60. ; Targeted device: PIC16F876A ; ; ***************************************************************************

; Declare the data areas used. cblock ADCResult:2 CelsiusPD:2 CelBin:2 Far:2 FarPD:2 WregTest ThreshPD:2 endc

Temperature1:

movlw 0

call AnalogConv ; Convert the A/D

call TestADCResult ; Put the A/D output to the LED display.

call FindCelsius ; Convert Value to celsius

btfsc PORTA,2 ; Is S1 closed? Skip next instruction goto DisplayCelsius ; call Celtofar

call UnpackFar ; Put value to LED buffer

goto Tempfinal DisplayCelsius:

call UnpackCel

; Put value to LED buffer

; ADC_Delay_us macro definition ; Input: w reg contains the # of microseconds to delay ADC_Delay_us macro

addlw 0xFF

btfss STATUS,Z

goto $-2 endm

; Start decrementing W reg ; See if W has been decremented to zero, skip if it is ; Jump back until it is zero

; AnalogConv a subroutine that will convert the voltage on ; the analog input channel contained in W reg ; Input: w reg has analog channel to convert ; Output: ADRESH has 2 MSB and ADRESL has lower 8 bits of 10 bit AnalogConv:

movwf WregTest

btfsc WregTest,0 bsf ADCON0,3

btfsc WregTest,1 bsf ADCON0,4

btfsc WregTest,2 bsf ADCON0,5

movlw .20

ADC_Delay_us

bsf ADCON0,2

movlw .30

ADC_Delay_us bsf STATUS,RP0

movf ADRESL,w bcf STATUS,RP0

movwf ADCResult

movf ADRESH,w

movwf ADCResult+1

bcf ADCON0,3 bcf ADCON0,4 bcf ADCON0,5 return

; Move analog channel to W reg Test ; Check each bit and set accordingly ; Check each bit and set accordingly ; Check each bit and set accordingly ; Move into W reg 20 for delay ; Delay the Microseconds in W reg ; Start a conversion ; Set up the ADC time delay ( 12 Tad cycles) ; Delay the Microseconds in W reg ; Move low byte to W reg ; Now move it to the analog Low location ; Move Higher byte to W reg ; Now move it to the analog High location ; Reset to channel 0

; FindCelsius a subroutine that will convert the A/D result ; to Celsius decimal digits. Since the result is ; 1 degree Kelvin per 2.5 bits, it is very hard to ; divide by 2.5, so we will multiply the result by ; 2 and divide by 5. After we do this lets convert ; it to celsius before we divide, so we have to subract ; by 273*5 =0x555. Then divide by repeated subtraction. ; Input: ADCResult has value to convert to Celsius ; Output: Digit0-3 has decimal celsius value (0 is LSD) FindCelsius:

bcf STATUS,C

rlf ADCResult,F

rlf ADCResult+1,F

subl16 ADCResult, 0x555

load16 CelsiusPD,0x9999

; Clear the carry first ; Rotate does a multiply by 2. ; Now put the carry through to the higher byte ; Subtract 273*5 =0x555 ; Start with value -1 (when incremented =0)

load16 CelBin,-1

FindCelsius2:

subl16 ADCResult, 5

IncDec16 CelsiusPD

inc16 CelBin

btfss ADCResult+1,7

goto FindCelsius2

addl16 ADCResult,5 return Celtofar:

mov16 CelBin,Far bcf STATUS,C rlf Far,f rlf Far+1,f rlf Far,f rlf Far+1,f rlf Far,f rlf Far+1,f

add16 CelBin,Far

addl16 Far,0xA0

load16 FarPD,0x9999 Celsius2Farh2:

subl16 Far, 5

IncDec16 FarPD

btfss Far+1,7

goto Celsius2Farh2 return

; Divide by 5 doing repeated subtraction ; Increment the celsius result ; Check to see if we went negative ; Add back in so it has remainder

; Start with value -1 (when incremented =0)

; Divide by 5 doing repeated subtraction ; Increment the celsius result ; Check to see if we went negative

; Unpack subroutine that uses the packed decimal and puts it into individual decimal digits. ; Input: CelsiusPD packed decimal digits ; Output: Digit0-3 has decimal celsius value (0 is LSD) UnpackCel:

movf CelsiusPD,w

andlw 0x0F

movwf Digit+1

swapf CelsiusPD,w

andlw 0x0F

movwf Digit+2

movf CelsiusPD+1,w

andlw 0x0F

movwf Digit+3

swapf CelsiusPD+1,w

andlw 0x0F

movlw 0x0C

; Get the Low data ; Only look at low nibble ; Get high nibble ; Get rid of high nibble ; Get the Low data ; Only look at low nibble ; Get high nibble ; Get rid of high nibble

movwf Digit+0 return ; Unpack2LCD subroutine that uses the packed decimal and puts it into LCD Buffer. ; Input: CelsiusPD packed decimal digits ; Output: LCD Buffer with decimal celsius value (0 is LSD) UnpackFar:

movf FarPD,w

andlw 0x0F

movwf Digit+1

swapf FarPD,w

andlw 0x0F

movwf Digit+2

movf FarPD+1,w

andlw 0x0F

movwf Digit+3

swapf FarPD+1,w

andlw 0x0F

movlw 0x0F

movwf Digit+0 return

; Get the Low data ; Only look at low nibble ; Get high nibble ; Get rid of high nibble ; Get the Low data ; Only look at low nibble ; Get high nibble ; Get rid of high nibble

; Unpack2LCD subroutine that uses the packed decimal and puts it into LED Buffer. ; Input: CelsiusPD packed decimal digits ; Output: LCD Buffer with decimal celsius value (0 is LSD) UnpackThresh:

movf ThreshPD,w ; Get the Low data

andlw 0x0F ; Only look at low nibble

movwf Digit+1

swapf ThreshPD,w ; Get high nibble

andlw 0x0F ; Get rid of high nibble

movwf Digit+2

movf ThreshPD+1,w ; Get the Low data

andlw 0x0F ; Only look at low nibble

movwf Digit+3

swapf ThreshPD+1,w ; Get high nibble

andlw 0x0F ; Get rid of high nibble

movlw 0x0C

movwf Digit+0 return

; TestADCResult subroutine that uses the ADC Result and puts it on the LED display. ; Input: CelsiusPD packed decimal digits ; Output: Digit0-3 has decimal celsius value (0 is LSD) TestADCResult:

movf ADCResult,w

andlw 0x0F

movwf Digit+1

swapf ADCResult,w

andlw 0x0F

movwf Digit+2

movf ADCResult+1,w

andlw 0x0F

movwf Digit+3

swapf ADCResult+1,w

andlw 0x0F

movwf Digit+4

movlw 0x0C

movwf Digit+0 return CheckThresh:

btfsc return

PORTA,2

Thermo:

btfsc PORTB,5

goto Temp2

bsf PORTA,5

btfsc Flags,0

goto Temp4 bsf Flags,0

IncDec ThreshPD

goto Temp4 Temp2: bcf Flags,0

bcf PORTA,5

; Get the Low data ; Only look at low nibble ; Get high nibble ; Get rid of high nibble ; Get the Low data ; Only look at low nibble ; Get high nibble ; Get rid of high nibble

; Check the threshold by pressing on switch 3

; This is just to test the push button 4 (count up) port with LED

; This is just to test the push button 4 (count up) PORTB5 with LED

Temp4:

btfsc PORTB,4

goto Temp3

bsf PORTA,5

btfsc Flags,1

goto Tempfinal bsf Flags,1

; This is just to test push button 5 (count up) PORTB4 with LED

Temp3: bcf Flags,1

bcf PORTA,5

DecDec ThreshPD

goto Tempfinal

; This is just to test push button 5 (count up) PORTB4 with LED

Tempfinal: return

LED Display Driver Code

;**************************************************************************** ; File Name: PicLEDDsplyDriver.asm ; Title: “PIC LED display Driving” ; ; Function: This assembly code will display data on a four 7 segment LED display driven on Port C, with digit selects on Port B 0-3 bits. ; The data will be in the RAM area Digit0 to Digit3. It must ; be a value 0 to 9 to be displayed. ; ; Developed using MPLAB version 8.60. ; Targeted device: PIC16F876A ; ; Pins Used: ; Oscillator is R-C network = 3.9k and 33pf => ~ 4MHz ; Port A: Not Used. ; Port B: Select bits 0-3 for the 4 digits, 0 being the right most digit. ; Port C: 7-0 set as output, with 7 seg disp 6=g,5=f,4=e,3=d,2=c,1=b,0=a. ; Port D: Not defined for this PIC ; Port E: Not defined for this PIC ; ; *************************************************************************** ; LED_Scan Routine. Shows the digits held in Display0-3 ; INPUTS: Digit 0-3 filled with the information to display ; OUTPUTS: none LED_Scan:

btfss PORTB,0 ; Check to see if digit 0 is selected (bit =0)

goto Display0 ; Jump because digit 0 is selected

btfss PORTB,1 ; Check to see if digit 1 is selected (bit =0)

goto Display1 ; Jump because digit 1 is selected

btfss PORTB,2 ; Check to see if digit 2 is selected (bit =0)

goto Display2 ; Jump because digit 2 is selected

btfss PORTB,3 ; Check to see if digit 3 is selected (bit =0)

goto Display3 ; Jump because digit 3 is selected

movlw b’00001110’ ; Set to select digit0 (active=0)

movwf PORTB ; Put it out to the Digit select

goto DisplayEnd Display0:

bsf PORTB,0 ; Set to deselect digit0

bcf PORTB,1 ; Clear the bit to select digit1

movf Digit+1,0 ; Move in digit 1 to W, we just selected it

call DispSeg ; Go put out that segment value

goto DisplayEnd Display1:

bsf PORTB,1 ; Set to deselect digit1

bcf PORTB,2 ; Clear the bit to select digit2

movf Digit+2,0 ; Move in digit 2 to W, we just selected it

call DispSeg ; Go put out that segment value

goto DisplayEnd

Display2:

bsf PORTB,2

bcf PORTB,3

movf Digit+3,0

call DispSeg

goto DisplayEnd Display3:

bsf PORTB,3

bcf PORTB,0

movf Digit,0

call DispSeg

goto DisplayEnd DisplayEnd: return

; Set to deselect digit2 ; Clear the bit to select digit3 ; Move in digit 3 to W, we just selected it ; Go put out that segment value

; Set to deselect digit3 ; Clear the bit to select digit0 ; Move in digit 0 to W, we just selected it ; Go put out that segment value

; DispSeg Routine. Translates the digit to segments and puts it out. ; INPUTS: Digit to display in W reg. ; OUTPUTS: none DispSeg:

call SegmentLookUp ; Translate the digit to the segment value

xorlw 0xFF ; Invert the W reg, because the port is - active

movwf PORTC ; Set Segment data W into port C

;xorlw 0xFF ; This is to activate the PORT A if we need to light on the red light ;movwf PORTC return

; IncDigits Routine. Increments the Digits in decimal format, one per byte. ; INPUTS: Decimal digit in Digit 0-3. ; OUTPUTS: The decimal digits incremented by 1.

IncDigits:

incf Digit,1 ; Increment the display count.

movfw Digit ; Get that digit to see if it exceeded 9

xorlw 0x0A ; see if the digit is a 0x0A which is above 9

btfss STATUS,Z ; If they were equal W would be 0, (Z=1), so skip next if Z=1

goto IncDigitEnd ; Jump because digit 0A was not found clrf Digit

incf Digit+1,1 ; Increment the display count.

movfw Digit+1 ; Get that digit to see if it exceeded 9

xorlw 0x0A ; see if the digit is a 0x0A which is above 9

btfss STATUS,Z ; If they were equal W would be 0, (Z=1), so skip next if Z=1

goto IncDigitEnd ; Jump because digit 0A was not found clrf Digit+1

incf Digit+2,1 ; Increment the display count.

movfw Digit+2 ; Get that digit to see if it exceeded 9

xorlw 0x0A ; see if the digit is a 0x0A which is above 9

btfss STATUS,Z ; If they were equal W would be 0, (Z=1), so skip next if Z=1

goto IncDigitEnd clrf Digit+2

incf Digit+3,1

movfw Digit+3

xorlw 0x0A

btfss STATUS,Z

goto IncDigitEnd clrf Digit clrf Digit+1 clrf Digit+2 clrf Digit+3 IncDigitEnd: return

; Jump because digit 0A was not found ; Increment the display count. ; Get that digit to see if it exceeded 9 ; see if the digit is a 0x0A which is above 9 ; If they were equal W would be 0, (Z=1), so skip next if Z=1 ; Jump because digit 0A was not found

Macros Code

;**************************************************************************** ; File Name: PIC16Macros.asm ; Title: “Supplies general purpose 16 bit macros” ; ; Function: This assembly code will provide 16 bit macros for general usage. ; ; Developed using MPLAB version 8.60. ; Targeted device: PIC16F876A but useful for all PICs ; ; *************************************************************************** ; All these macros use the “Little Endian” style of data storage organization. ; The Least Significant Byte is stored first ( like 0x20) and Most Significant ; byte is stored in the next higher address ( 0x21 ). ; add16 macro does a unsigned 16 bit addition with carry out. The Source is preserved; Destination is replaced, with Carry set appropriately. (assume high byte is +1 in the General Purpose data area) ; Input: Destination and Source ; Output: Destination add16 macro Destination,Source

movf Source,w

; Get low byte

addwf Destination,f ; Add to the Destination

movf Source+1,w ; Get high byte

btfsc STATUS,C

; See if carry

incf Source+1,w ; Add if carry

addwf Destination+1,f ; Add high byte into Destination endm

; load16 macro loads up a 16 bit value into a variable ; Input: Immediate literal value ; Output: Variable loaded with data load16 macro Variable, Literal

movlw low (Literal) ; Get the low byte of the immediate value (Literal)mod256.

movwf Variable ; Put it in the desired variable

movlw high (Literal) ; Now use the upper 8 bits (Literal)/256

movwf Variable+1 ; Move it into the upper 8 bits.

endm

; addl16 macro will add a 16 bit variable to a literal or immediate value ; Input: Literal or immediate value, and Destination ; Output: Result is in Destination, carry set appropriately addl16 macro Destination, Literal

movlw low(Literal) ; Get the low 8 bits of the Literal

addwf Destination,f ; Add it to the low of the Dest.

movlw high(Literal) ; Now get the upper 8 bits of the Lit.

btfsc STATUS,C ; Jump over the movlw if C=1

movlw (high(Literal))+1 ; If no carry, get the upper 8 plus 1

addwf (Destination)+1,f ; Finish off by adding it to the high 8 endm

; sub16 macro will accomplish a 16 bit unsigned subtraction with carry out. ; The Source is subtracted from the Destination and carry (-borrow) ; is set appropriately. ; Input: Source and Destination variables ; Output: Destination has the result and the carry (-borrow) is set appropriately sub16 macro Destination, Source

movf Source,w

; Get low byte of what is being subtracted

subwf Destination,f ; Subtract low byte of the Source from low byte Dest.

movf Source+1,w ; Now get high byte of subtrahend

btfss STATUS,C ; If there was a borrow, we inc ( if -B is inactive skip inc)

incf Source+1,w ; the Source high byte instead of decrementing the Dest.

subwf Destination+1,f ; Subtract the high byte of Destination - Source endm ; subl16 macro will accomplish a 16 bit unsigned subtraction with Literal value, with carry out. The Literal is subtracted from the Destination and carry (-borrow) is set appropriately. ; Input: Source and Destination variables ; Output: Destination has the result and the carry (-borrow) is set appropriately subl16 macro Destination, Literal

movlw low (Literal) ; Get low byte of what is being subtracted

subwf Destination, f ; Subtract the low Literal from low byte Destination

movlw high (Literal) ; Get the high byte of Literal

btfss STATUS,C ; If -Borrow is active low, s

movlw (high (Literal))+1 ; Replace it, if borrow active, with an incremented Literal subwf Destination+1,f ; Now subtract endm

; mov16 macro moves 16 bits of information from the Source to the Destination ; Input: Source with 16 bits of information ; Output: Destination with the SourceĂ­s information mov16 macro Source, Destination

movf Source,w ; Get the source low

movwf Destination ; Put it into the destination low

movf Source+1,w ; Do the same for the source high

movwf Destination+1 ; And destination high endm ; inc16 macro will increment a 16 bit value, and sets Z appropriately. ; Input: Destination which will have 1 added to it. ; Output: Destination inc16 macro Destination

incfsz Destination,w ; Increment the low byte

decf Destination+1,f ; No carry (negates next step)

incf Destination+1,f ; Add one to high byte

movwf Destination ; Store updated low byte back.

iorwf Destination+1,w ; Set the z flag appropriately endm

; twoscom16 macro will do a 2Ă­s compliment of a 16 bit value ; Input: Destination value to find the 2Ă­s compliment of ; Output: Destination twoscom16 macro Destination

comf Destination ; First compliment the 16 bit value comf Destination+1

inc16 Destination ; Then add 1 using the increment 16 bit macro. endm

; There must be a 16 bit register defined that is used by the 16 BIT operations

cblock 0x7e _Xreg endc ; cmp16 macro compares two 16 bit unsigned values A and B, returns Z and C set appropriately ; Input: A and B values ; Output: Flags set where if Z=1 then A & B are equal, if C=1 then A>B, and if C=0 then A<B. cmp16 macro A, B

mov16 A, _Xreg ; Use the 16 bit move macro

sub16 _Xreg,B ; Now subtract using the 16 bit macro

movf _Xreg,w ; Set the Z flag bit

iorwf _Xreg+1,w ; The OR only changes the Z flag bit. endm

; IncDec macro to increment a variable in packed decimal ; Input: Packed Decimal number address. ; Output: Packed Decimal number incremented, C set if overflow IncDec macro PD

incf PD,f ; Increment the packed decimal normal

movf PD,w ; Move byte into W

andlw 0x0F ; Only look at lower 4 bits.

sublw 0x0A ; Sub w from literal: 0A - W

bcf STATUS,C ; Clear the Carry Flag

btfss STATUS,Z ; if equal skip next opcode

goto $+.10 ; Low decimal digit OK, so jump.

movlw 0x06 ; Set up W to add 06 to PackDec

addwf PD,f ; Add the 06 to correct

movf PD,w ; Get the PackDec again

sublw 0xA0 ; See if upper digit has overflowed.

bcf STATUS,C ; Clear the Carry

btfss STATUS,Z ; if equal skip next opcode

goto $+3 ; Jump if not exceeded digit.

movlw 0x60 ; Correct upper digit

addwf PD,f ; Add it in to PackDec endm

DecDec macro PD

decf PD,f

movf PD,w

andlw 0x0F

sublw 0x0F

bcf STATUS,C

btfss STATUS,Z

goto $+.10

movlw 0x0F

subwf PD,f

movf PD,w

sublw 0x06

bcf STATUS,C

btfss STATUS,Z

goto $+3

movlw 0x0F

subwf PD,f endm

; Decrement the packed decimal normal ; Move byte into W ; Only look at lower 4 bits. ; Sub w from literal: 0A - W ; Clear the Carry Flag ; if equal skip next opcode ; Low decimal digit OK, so jump. ; Set up W to subtract 0F to PackDec ; Subtract the 06 to correct ; Get the PackDec again ; See if upper digit has overflowed ; Clear the Carry ; if equal skip next opcode ; Jump if not exceeded digit. ; Correct upper digit ; Subtract it in to PackDec

; IncDec16 macro to increment a 16bit variable in packed decimal ; Input: Packed Decimal number address. ; Output: Packed Decimal number incremented, C set if overflow IncDec16 macro PD

IncDec PD ; Call the macro

btfss STATUS,C ; Skip if carry, jump if not

goto $+2

IncDec PD+1 ; Call the macro endm

Digital Thermometer Schematics