DS18S20 displays wrong temperatures

[Shozo Kanamori]

Hi Lotondo,

The article you introduced me seems to be very helpful. I have browsed a lot of webpages but never come across this article before. I will soon start my experiment using DS18B20.

Thank you.

Shozo Kanamori

[Lotondo]

Nice to read that my link maybe helpful.
By the way, I have trouble using ds18S20 with temperature below 0° celsius
if you see some code regarding how to use it, pls link it to me.
Thanks
Bye

[Bruce]

Darell Taylor has some very nice temp conversion routines here http://www.pbpgroup.com/ you might also find very useful.

[Darrel Taylor]

Thanks Bruce!

I was talking with someone else off forum that had problems using the conversion routines with a DS1820 and negative temperatures, so I came up with this.

Sign  VAR  BIT
TempC VAR  WORD

Sign = temperature.15
TempC = ABS(temperature)
TempC =(TempC>>1)*10 + (TempC.0 * 5)
IF Sign then TempC = 0 - TempC

He said it worked, but I haven't tried it myself.

HTH,
  Darrel