Temperature Conversion

[iian_stew]

Hello everyone,

I am having a little problem with the DS18B20. I have been using the readtemp command so far and the temperature return has been working fine.

I now want to start using the readtemp12 command for increased resoution.

I would like to know how the conversion works. I would like to be able to do the folowing. I am putting together a school experiment and want to do the following.

I want the students to tabulate the values of temperature in degrees and also to tabulate the 12bit value. So I think I will need to use the readtemp and the readtemp12 value.

I hope this makes sense!

Also, does anyone know what the conversion is?


Thanks so much

 

[MORA99]

There is alot of threads on the same subject, try search for DS18B20.

The value from readtemp12 is temperature*16, the first 3 bits are signbits that shows if the temperature is below 0.
The readout is not twos complement, but just regular binary, and if a signbit is set, its below 0.

But theres a lot of code on the forum already, so you dont have to write it yourself.

 

[BrendanP]

Have a look on phandersons web site, he has code examples ready to go.

 

[kevrus]

check out this thread that I started as I struggled with the negative temp conversion...the posts explains things quite clearly...good luck

http://www.picaxeforum.co.uk/showthread.php?t=8329