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568

Chapter 16

16.4 Sample Programs

The following sections contain the sample programs discussed in this chapter.

16.4.1 ADF84 Program

;File name: ADCF84.asm

;Last Update: June 8, 2006

;Author: Julio Sanchez

;Processor: 16F84A

;Description:

;Program to demonstrate use of the ADC0831 Analog to

;Digital converter with the 16F84 PIC. Program reads the

;value of a potentionmeter connected to Port-A, line 0

;and displays resistance in the range 0 to 255 on the

;attached LCD.

;Circuit:

;

ADC0831

16F84

CIRCUIT

; PIN LINE

;6 DO ------------- RB0

;7 CLK ------------- RB1

;1 CS ------------- RB2

;2 Vin+ ------------------------------ POT2

;3 Vin- ------------------------------ GND

;5 Vref ------------------------------ +5v

;8 Vcc ------------------------------ +5v

;For LCD display parameters see the LCDTest2 program.

;WARNING:

;Code assumes 4Mhz clock. Delay routines must be

;edited for faster clock

;

;===========================

;switches ;===========================

;Switches used in __config directive:

;

_CP_ON

Code protection ON/OFF

; *

_CP_OFF

;

*

_PWRTE_ON

Power-up timer ON/OFF

;_PWRTE_OFF

;

_WDT_ON

Watchdog timer ON/OFF

; * _WDT_OFF

;

_LP_OSC

Low power crystal

oscillator

; * _XT_OSC

External parallel

resonator/crystal oscillator

;

_HS_OSC

High speed crystal resonator (8 to

10 MHz)

;

Resonator: Murate

Erie CSA8.00MG =

8 MHz

;

_RC_OSC

Resistor/capacitor oscillator

Analog to Digital and Realtime Clocks

569

; |

(simplest, 20% error)

;|

;|_____ * indicates setup values presently selected

;========================= ; setup and configuration ;=========================

processor

16f84A

include

<p16f84A.inc>

__config

_XT_OSC & _WDT_OFF & _PWRTE_ON & _CP_OFF

errorlevel -302

; Suppress bank-related warning

;============================================================

; M A C R O S

;============================================================ ; Macros to select the register banks in 16F84

Bank0

MACRO

; Select RAM bank 0

bcf

STATUS,RP0

ENDM

Bank1

MACRO

; Select RAM bank 1

bsf

STATUS,RP0

ENDM

;=====================================================

;

constant definitions

; for PIC-to-LCD pin wiring and LCD line addresses

;=====================================================

#define E_line 1

;|

#define RS_line 2

;| — from circuit wiring diagram

#define RW_line 3

;|

; LCD line addresses (from LCD data sheet)

#define LCD_1 0x80

; First LCD line constant

#define LCD_2 0xc0

; Second LCD line constant

;Note: The constants that define the LCD display line

;addresses have the high-order bit set in

;order to facilitate the controller command

;Defines from ADC0831 wiring diagram

;all lines in Port-A

#define

DO

0

;|

#define

CLK

1

;| — from circuit wiring diagram

#define

CS

2

;|

;

;=====================================================

;

variables in PIC RAM

;=====================================================

; Reserve 16 bytes for string buffer

; Start of block ; Counter # 1
; Counter # 2
; Counter # 3
; Storage for start of text area ; counter J
; counter K
; Index into text table (also used ; for auxiliary storage)
; Local temporary storage ; Storage # 2
; Received data

570

Chapter 16

cblock 0x0c strData

endc

;Reserve three bytes for ASCII digits cblock 0x1d

asc100

asc10

asc1 endc

;Continue with local variables

cblock 0x20 count1 count2 count3 pic_ad

J

K index

store1

store2 rcvdata bitCount

; Storage for ASCII decimal conversion and digits

inNum

;

Source operand

thisDig

;

Digit counter

endc

;=========================================================

; program

;=========================================================

org

0

; start at address

goto

main

; Space for interrupt handlers

org

0x08

main:

Bank1

movlw

b’00000000’

movwf

TRISA

movlw

b’00000001’

movwf

TRISB

Bank0

movlw

b’00000000’

movwf

PORTA

movwf

PORTB

; Wait and initialize HD44780 call delay_5

;All lines to output

;in Port-A

;B line 0 to input

;All outputs ports low

;Allow LCD time to initialize

;itself

Analog to Digital and Realtime Clocks

571

call

delay_5

call

initLCD

; Then do forced

initialization

call

delay_5

; Wait again

; Store base address of text buffer in PIC RAM

movlw

0x0c

; Start address for buffer

movwf

pic_ad

; to local variable

;======================

;first LCD line ;======================

;Store 16 blanks in PIC RAM, starting at address stored

;in variable pic_ad

call blank16

;Call procedure to store ASCII characters for message

;in text buffer

movlw

d’0’

; Offset into buffer

call

storeMS1 ; Store message text in buffer

; Initialize ADC0831

nextAna:

call

ana2dig

; Read analog line

call

delay_125

; Display result

movf

rcvdata,w

call

bin2asc

; Conversion routine

;At this point three ASCII digits are stored in local

;variables. Move digits to display area

movf

asc1,w

; Unit digit

movwf

.26

; Store in buffer

movf

asc10,w

; same with other digits

movwf

.25

movf

asc100,w

movwf

.24

;Display line

;Set DDRAM address to start of first line

call line1

; Call procedure to display 16 characters in LCD call display16

call long_delay goto nextAna

;============================================================ ; initialize LCD for 4-bit mode ;============================================================ initLCD:

;Initialization for Densitron LCD module as follows:

;4-bit interface

;2 display lines of 16 characters each

;cursor on

572

Chapter 16

;left-to-right increment

;cursor shift right

;no display shift ;=======================|

;

set command mode

|

;=======================|

bcf

PORTA,E_line

; E line low

bcf

PORTA,RS_line

; RS line low

bcf

PORTA,RW_line

; Write mode

call

delay_125

; delay 125 microseconds

;***********************|

;

FUNCTION SET

|

;***********************|

movlw

0x28

; 0 0 1 0 1 0 0 0 (FUNCTION SET)

call

send8

; 4-bit send routine

; Set 4-bit mode command must be repeated

movlw

0x28

call

send8

;***********************|

; DISPLAY AND CURSOR ON |

;***********************|

movlw

0x0e

; 0 0 0 0 1 1 1 0 (DISPLAY ON/OFF)

call

send8

;***********************|

;

set entry mode

|

;***********************|

movlw

0x06

; 0 0 0 0 0 1 1 0 (ENTRY MODE SET)

call

send8

;***********************|

; cursor/display shift

|

;***********************|

movlw

0x14

; 0 0 0 1 0 1 0 0 (CURSOR/DISPLAY

SHIFT)

call

send8

;***********************|

;

clear display

|

;***********************|

movlw

0x01

; 0 0 0 0 0 0 0 1 (CLEAR DISPLAY)

call

send8

; Per documentation

call

delay_5

; Test for busy

return

;=======================

;

Procedure to delay

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