Page 137 - Making PIC Microcontroller Instruments and Controllers

SOCKETS IAND UAI i27
U7

lilt9.idf]lti9il Using the DS1820 (Program to read lemperalure bv
Labs) (Cont ued)
micrcEngineering
ADCON1 =%OOOOO111 ; set PORTA and PORTE to digitaf
LOW PORTE.2 ; lcd x/w line 1ow (v)
PAUSE 100 ; wait for 1c.l to start
LCDOUT $FE, 1, \[EMP IN DEGREES C" ; display siern-on nessalre

; nainloop to read the tenperaiure and dispLav on tcd
UAINLOOP:
GOSUB INIT182O ; init the Ds 180 2
COIAIAnD = %11001100 ; issue skip ron conaand
GOSUs WRrTE1820
CO!{DiAND = %01000100 ; start lemperature
GOSIIB !rRrTE1820
PAUSE 2000 ; wait 2 seconds for converslon to

GOSUB INIT182O ; do another lnit
-
COMMAIiID %L1OO11OO ; issue skip ron comand
GOST'B I'IRITE182O
COMMAND = %10111110 ; read lhe tempetalure
GOSUB WRTEE182O
GOSUB RE]AD182O
; display the decinal temperatu.e
LCDOUT $FE, 1, DEC (TE!'P >> 1), \.4/ DEC (IEMP.o * 5),
\ DEGREES CZ
GOTO MAINIOOP
inirialize Ds1802 and check for

ITiIITIS2O:
LOW DQ Set lhe data pin 1ow ho init
PAUSEUS 5OO
release data pin {set to input
for hish)
PAUSEUS 100
I F D Q = l T E E A !
I,CDOUE SFE, 1, 'DS182O NOT PRESE!fT" ;
PAUSE 500
GOTO MAINI.OOP
ENDIF
PAUSEnS 400 ldait for end of presence pulse
RETURN
vrile "comand" byte ho the ds1820
WRITE1820 !
F O R I = 1 T O 8 I bits Lo a byte
I F C O U M A N D - o = 0 t l t E N
GOSUB VTRITEO
EI"SE
GOST'B IIRITEI