System Temperature Acquisition

1.1 Brief Explanation of Concepts

Explanation of the differences among three temperature concepts.

Item/Name	Range	Description
Ambient Temperature	Commercial: -20℃ ~ +80℃ Industrial: -40℃ ~ +85℃	Commonly known as room temperature
Chip Package Temperature	Slightly lower than junction temperature	Temperature of the chip package and heat dissipation components
System Temperature	+115℃を超えないこと	Temperature of semiconductor devices inside the chip, commonly called Junction Temperature

本文では、主にジャンクション温度についてDescriptionします。

1.2 Operation Method

1.2.1 Queryable Module

Using the find command, you can see that the chip only supports reading the junction temperature of a single area (chip center).

find /sys -name temp

1.2.2 Query Operation

Use the cat command to check the junction temperature at the chip center as follows.

cat /sys/devices/virtual/thermal/thermal_zone0/temp

If the read value is ‘40810’, it indicates that the current junction temperature at the chip center is 40.810°C.

1.3 Additional Information

Users can enter the directory of a specific junction temperature zone to view detailed information. For example, for the chip-center junction temperature zone:

cd /sys/devices/virtual/thermal/thermal_zone0/

ls

A group of trip_point entries is displayed here. These trip_point parameters can be configured in the device tree.

When the junction temperature of the corresponding zone reaches or exceeds the trip_point_0_temp setting (default +115°C) and remains in that state for the duration specified by trip_point_0_hyst, the entire chip will automatically reboot.