Thermal Zone

Thermal management is necessary to ensure proper operation of the phyCORE-AM64x SOM, especially when integrated inside an enclosure. The AM64x processor generates considerable heat, so it is important to manage the system’s temperature. The phyCORE-AM64x has a temperature rating of -40°C to 85°C. This guide will show you how to read the junction temperature of the processor on the phyCORE-AM64x SOM. To learn more information about the phyCORE-AM64x thermal management, please see section 4.10 in the Hardware Manual.

Reading the Temperature

The phyCORE-AM64x processor has 2 physical location (thermal zone) where the temperature can be monitored. The available zones can be accessed in the Linux directory /sys/class/thermal/thermal_zone0 or /sys/class/thermal/thermal_zone1.

To output the temperature of thermal zone 0 run the following command:

Target (Linux)

cat /sys/class/thermal/thermal_zone0/temp

Expected Output

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.

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.

For more details on thermal zone terminology, please refer to the kernel documentation: thermal zones.

To view the type of trip points and the trip point temperatures of thermal zone 0 use the following command:
Target (Linux)
```
cat /sys/class/thermal/thermal_zone0/trip_point*
```
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 will turn off when the temperature reaches 103C.

Note

Learn more about the thermal management driver from Texas Instruments Kernel Driver Guides.