david95:
Ok, I connected wrong the GND, so it wasn't working, but now I connected it well and it says Temperature: 85 CMaybe it's broken ?
Probably not, they can take a lot of abuse, you will be glad to hear. And I'm glad to hear I'm not the only person to wire one the wrong way round.
The 85 c is the power-on reset value.
The DS18B20 may not be receiving the command to perform a temperature conversion. This could be a software screwup. You may be asking for a readout before you execute the get command, or are simply not giving it enough time to do the job. Indeed, looking at the code, a one second delay in your loop could work wonders here.
The problem may also be caused by inadequate power here. If you are using USB power, a wall wart could be a good investment right now.