DS1620 -BS2e-code - How to turn on a light using a thermometer ?

guy20sanjose

Hello
I'm using a bs2e on a board of education and a DS1620 thermometer. I'd like to know how to write some code to the program below to turn a light on and of with setting temp points. Any help is appreciated.

' {$STAMP BS2e}
' {$PBASIC 2.5}
'

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[ Program Description ]

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'
' This program measures temperature using the Dallas Semiconductor DS1620
' temperature sensor. Resolution is 0.5 degrees Celsius.
'

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[ I/O Definitions ]

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Page 162 • StampWorks
DQ CON 0 ' DS1620.1 (data I/O)
Clock CON 1 ' DS1620.2
Reset CON 2 ' DS1620.3
'

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[ Constants ]

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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
RdCntr CON $A0 ' read counter
RdSlope CON $A9 ' read slope
StartC CON $EE ' start conversion
StopC CON $22 ' stop conversion
WrCfg CON $0C ' write config register
RdCfg CON $AC ' read config register
DegSym CON 186 ' degrees symbol
'

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[ Variables ]

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tempIn VAR Word ' raw temperature
sign VAR tempIn.BIT8 ' 1 = negative temperature
tC VAR Word ' Celsius
tF VAR Word ' Fahrenheit
tHi VAR Word
tLo VAR Word
'

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[ Initialization ]

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Setup:
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
DEBUG CLS,
"DS1620 ", CR,
"

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"

'

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[ Program Code ]

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Main:
DO
GOSUB Read_DS1620 ' get the temperature
Display_C:
DEBUG CRSRXY, 0, 2,
(tC.BIT15 * 13 + " "),
DEC (ABS tC / 10), ".", DEC1 (ABS tC),
DegSym, " C", CLREOL
Display_F:
DEBUG CRSRXY, 0, 3,
(tF.BIT15 * 13 + " "),
DEC (ABS tF / 10), ".", DEC1 (ABS tF),
DegSym, " F", CLREOL
PAUSE 1000 ' delay between readings
LOOP
'

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[ Subroutines ]

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Read_DS1620:
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
tempIn.BYTE1 = -sign ' extend sign bit
tC = tempIn * 5 ' convert to tenths
IF (tC.BIT15 = 0) THEN ' temp C is positive
tF = tC */ $01CC + 320 ' convert to F
ELSE ' temp C is negative
tF = 320 - ((ABS tC) */ $01CC) ' convert to F
ENDIF

ENDIF
RETURN

How to turn a light on when tF > 88 F, turn off when tF < 88 F ? What code and where do I need to add?
Thank again.

Tracy Allen

There is a little tutorial at, http://www.emesystems.com/OL2d1620.htm#thermostat

guy20sanjose

Thanks Tracy
I don't understand this code:

SHIFTOUT 15,14,LSBFIRST,[1,15\9] ' upper threshold=15/2=7.5 deg C

How do I make change to it to make it upper threshold = 28 deg C ?
Please help

Tracy Allen

Take your desired temperature, 28 deg C, and multiply it times two. That's 56. Plug that into the SHIFTOUT command (adjusted for whatever pins you are using):

SHIFTOUT 15,14,LSBFIRST,[1,56\9] ' upper threshold=56/2=28 deg C

The \9 after the 56 simply tells the Stamp to shift out 9 bits. That is what is required by the DS1620, so that it can do temperatures both above and below freezing.