Thermal Zone

This guide will show you how to read the junction temperature of the processor on the phyCORE-AM65x SOM. Your SOM should come with a heat sink and fan installed to keep the processor below the set trip points and within specified operating temperature. 

Step-by-step guide

Reading the Temperature

The TI AM65x processor has three physical locations where the temperature can be monitored (thermal zones). Each zone can be accessed in the following Linux directories. 

Thermal Zone
/sys/class/thermal/thermal_zone0
/sys/class/thermal/thermal_zone1
/sys/class/thermal/thermal_zone2

The below command can be used to output the temperature of thermal zone 0. This same command can be used for zones 1 and 2. 

Target (Linux)
cat /sys/class/thermal/thermal_zone0/temp

This output translates to 41.4C:

Expected Output
root@am65xx-phycore-kit:~# cat /sys/class/thermal/thermal_zone0/temp
41400

Temperature Trip Points

Each thermal zone includes trip points. You can set the trip points to a temperature that will trigger an event, such as turning on a fan for active cooling. You can also build in a critical trip point; if this temperature is reached, Linux will automatically shutdown the system for protection of the processor. 

An example below shows how to view the trip point of thermal zone 0. In this example there is a critical trip point when the temperature reaches 125C. 

Example Usage
root@am65xx-phycore-rdk:~# cat /sys/class/thermal/thermal_zone0/trip_point_0_type
critical
root@am65xx-phycore-rdk:~# cat /sys/class/thermal/thermal_zone0/trip_point_0_temp
125000