Some people say that it first shows a burst of 85 degrees Celsius, then it returns to normal; some people say that occasional 85 degrees Celsius problem; some people say that always 85 degrees Celsius. The reasons for the analysis are as follows:

1. Hardware connection problems: pull-up resistance problem, welding problem, pin short circuit, GX18B20 breakdown, power supply problem

2. The value of temperature register after power-on reset is + 85 C.

3. External interference is too great

4. Software problems: incorrect timing, no ROM matching skipped, insufficient power-on delay

Note: GX18B20 has negative voltage characteristics. When the power supply is reversed, the chip will not burn out due to fever, but can not work properly.

Summary: When the program is out of order, we need to check the delay program carefully to see if the delay is accurate; then check the reset and read-write program, whether it conforms to the sequence of components, and check whether the reset is successful; when reading the temperature, pay attention to the temperature conversion time after the temperature conversion, and provide a certain and sufficient delay, not to read immediately.