DS18s20 - negative teperature
WHAT IS WRONG HERE ?!
i heave 2 sensors DS18S20 in one wire network , 4,7 k resitor pullup,
3 wires / Vcc = 5V , GND, data
1.with positive temerature works OK.
2.with negative teperature around 0°c is jumping from -655.11 to +88.xx , then i heave right data ,after some time is jumping again and again .....or is jumping from -655.11 to right data and back.
PIC16F877 AT 4 MHZ
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count_remain_0 Var Byte ' sensor 0
count_per_c_0 Var Byte ' sensor 0
count_remain_1 Var Byte ' sensor 1
count_per_c_1 Var Byte ' sensor 1
TempC0 VAR WORD ' RAW Temperature readings sensor 0
R_Temp0 VAR WORD ' RAW Temperature readings sensor 0
TempC1 VAR WORD ' RAW Temperature readings sensor 1
R_Temp1 VAR WORD ' RAW Temperature readings sensor 1
Deg CON 223 ' Data to display Deg ° symbol
Sign0 VAR BYTE ' +/- sign for temp display sensor 0
Sign1
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'sensor 0
OWOUT PortB.0, 1, [$55,$10,$BB,$40,$2C,$00,$08,$00,$F9, $44] ' match ROM & do temp conversion
pause 50
OWOUT PortB.0, 1, [$55,$10,$BB,$40,$2C,$00,$08,$00,$F9, $BE] ' match ROM & read scratchpad memory
OWIN PortB.0, 2, [R_Temp0.Lowbyte, R_Temp0.Highbyte,skip 4,count_remain_0,count_per_c_0] '
if R_Temp0.bit9 = 0 then 'temp pozitive
sign0="+"
TempC0 = (((R_Temp0>> 1) * 100) - 25) + (((count_per_c_0 - count_remain_0) * 100) / count_per_c_0)
else
sign0="-" 'temp negative
R_Temp0 = R_Temp0.lowbyte ^%11111111
R_Temp0 = R_Temp0.lowbyte + 1
R_Temp0 = R_Temp0.lowbyte>> 1
TempC0 = (((R_Temp0>> 1) * 100) - 25) + (((count_per_c_0 - count_remain_0) * 100) / count_per_c_0)
endif
lcdout $FE , 1 ,sign0,DEC TEMPC0 DIG 3,DEC TEMPC0 DIG 2 ,".",DEC TEMPC0 DIG 1,DEC TEMPC0 DIG 0 ,Deg,"C","
....
