' {$STAMP BS2}
' ==============================================================================
'
' File...... Ex28 - DS1620.BS2
' Purpose... Temperature measurement
' Author.... Parallax
' E-mail.... stamptech@parallaxinc.com
' Started...
' Updated... 01 MAY 2002
'
'
' ==============================================================================
' ------------------------------------------------------------------------------
' Program Description
' ------------------------------------------------------------------------------
' This program measures temperature using the Dallas Semiconductor DS1620
' temperature sensor.
' ------------------------------------------------------------------------------
' I/O Definitions
' ------------------------------------------------------------------------------
DQ CON 0 ' DS1620.1 (data I/O)
Clock CON 1 ' DS1620.2
Reset CON 2 ' DS1620.3
' ------------------------------------------------------------------------------
' Constants
' ------------------------------------------------------------------------------
RdTmp CON $AA ' read temperature
WrHi CON $01 ' write TH (high temp)
WrLo CON $02 ' write TL (low temp)
RdHi CON $A1 ' read TH
RdLo CON $A2 ' read TL
StartC CON $EE ' start conversion
StopC CON $22 ' stop conversion
WrCfg CON $0C ' write config register
RdCfg CON $AC ' read config register
' ------------------------------------------------------------------------------
' Variables
' ------------------------------------------------------------------------------
tempIn VAR Word ' raw temperature
sign VAR tempIn.Bit8 ' 1 = negative temperature
tSign VAR Bit
tempC VAR Word ' Celsius
tempF VAR Word ' Fahrenheit
' ------------------------------------------------------------------------------
' Initialization
' ------------------------------------------------------------------------------
Initialize:
HIGH Reset ' alert the DS1620
SHIFTOUT DQ, Clock, LSBFirst, [WrCfg, %10] ' use with CPU; free-run
LOW Reset
PAUSE 10
HIGH Reset
SHIFTOUT DQ, Clock, LSBFirst, [StartC] ' start conversions
LOW Reset
' ------------------------------------------------------------------------------
' Program Code
' ------------------------------------------------------------------------------
Main:
GOSUB Get_Temperature ' read the DS1620
DEBUG Home
DEBUG "DS1620", CR
DEBUG "------", CR
DEBUG SDEC tempC, " C ", CR
DEBUG SDEC tempF, " F ", CR
PAUSE 1000 ' pause between readings
GOTO Main
' ------------------------------------------------------------------------------
' Subroutines
' ------------------------------------------------------------------------------
Get_Temperature:
HIGH Reset ' alert the DS1620
SHIFTOUT DQ, Clock, LSBFIRST, [RdTmp] ' give command to read temp
SHIFTIN DQ, Clock, LSBPRE, [tempIn\9] ' read it in
LOW Reset ' release the DS1620
tSign = sign ' save sign bit
tempIn = tempIn / 2 ' round to whole degrees
IF (tSign = 0) THEN No_Neg1
tempIn = tempIn | $FF00 ' extend sign bits for negative
No_Neg1:
tempC = tempIn ' save Celsius value
tempIn = tempIn */ $01CC ' multiply by 1.8
IF (tSign = 0) THEN No_Neg2 ' if negative, extend sign bits
tempIn = tempIn | $FF00
No_Neg2:
tempIn = tempIn + 32 ' finish C -> F conversion
tempF = tempIn ' save Fahrenheit value
RETURN