Thermal Zones

Thermal management is necessary to ensure proper operation of the phyCORE-AM57x SOM, especially when integrated inside an enclosure. This guide will show you how to read the junction temperature of the processor on the phyCORE-AM57x SOM. The development kit is shipped with a heat sink installed to keep the processor below the set trip points and within specified operating temperature. To learn more information about the phyCORE-AM57x thermal management, please see section 30 in the Hardware Manual.

Reading the Temperature

  • The TI AM57x processor has 5 physical locations where the temperature can be monitored (thermal zones). Each zone can be accessed in the following sysfs directories.

    Thermal Zones

    Sysfs Paths

    /sys/class/thermal/thermal_zone0

    /sys/class/thermal/thermal_zone1

    /sys/class/thermal/thermal_zone2

    /sys/class/thermal/thermal_zone3

    /sys/class/thermal/thermal_zone4

  • The below command can be used to output the temperature of thermal zone 0. This same command can be used for zones 1 through 4.

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

  • This output translates to 65.4°C:

Example Output
65400

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.

Thermal Trip Points

Trip Point Type

Description

Passive

Passive cooling: Mitigate heat by scaling down performance without active cooling.

Active

Active cooling: Implement more aggressive cooling methods to prevent the system from reaching critical temperatures.

Hot

Reaching operating threshold: Signals a state where the system is getting warm but hasn’t reached critical levels yet.

Critical

Exceeding critical threshold: Protect the hardware from potential damage due to extreme temperatures by forcing shutdown.
Default Thermal Zone Trip Points

Thermal Zone

Trip Point Number

Temperature

Hysteresis

Type

thermal_zone0

trip_point_0

trip_point_1

90°C

105°C

2°C

2°C

Passive

Critical

thermal_zone1

trip_point_0

105°C

2°C

Critical

thermal_zone2

trip_point_0

105°C

2°C

Critical

thermal_zone3

trip_point_0

105°C

2°C

Critical

thermal_zone4

trip_point_0

105°C

2°C

Critical

Hysteresis refers to a temperature margin before taking corrective actions, such as adjusting cooling mechanisms. Instead of reacting immediately when a certain temperature threshold is crossed, a hysteresis value ensures that the system doesn’t oscillate rapidly between different states due to small temperature fluctuations.

  • To view the type of trip points and the trip point temperatures of thermal zone 0 trip point 1, run the following command:

Target (Linux)
cat /sys/class/thermal/thermal_zone0/trip_point_1*
Expected Output
2000
105000
critical

The critical trip point which will cause the system to shutdown will be reached when the temperature reaches 105C and alarm when the temperature reaches 103C.