Fan
The phyBOARD-Electra AM64x includes a 4-pin Hirose connector at X12 for fan connectivity, designed for mounting the fan directly onto the processor heat sink for thermal management. The fan’s 5V power output can be controlled through a general-purpose control signal. When the control signal is set to a low state (0), the fan is powered on. Conversely, setting the control signal to a high state (1) turns off the 5V supply to the fan connector. This guide will demonstrate how to test your connections to the 4-pin Hirose connector at X12. For additional information on phyCORE-AM64x thermal management and fan operation, please refer to the Fan section in the Hardware Manual.
Requirements
The phyBOARD-Electra AM64x does not include a heat sink and fan. The below are the two fans that were tested on the PHYTEC hardware:
Item |
Description |
Link |
|---|---|---|
Heat Sink |
(29mmx29mmx9.5mm) |
|
Fan |
DC axial fan, 30mm square x 10mm |
|
Female Connector |
4 pin keyed header |
|
Crimping Terminals |
4x crimping jackets |
Recommended Header Configuration
Pin |
Signal |
Wire Color |
|---|---|---|
1 |
VCC_5V0_SW |
Red |
2 |
GND |
Black |
3 |
FAN_FG |
Yellow |
4 |
PWM |
Blue |
Hardware Setup
Connect fan to the 4-pin Hirose connector at X12.
Enabling the Overlay
Power on the development kit and stop in U-boot.
Load the device tree overlay required for exporting the GPIO signal that controls the fan and then boot the board.
sh-uboot:~# setenv overlays k3-am642-phyboard-electra-gpio-fan.dtbo sh-uboot:~# boot
Note
For more information about overlays see chapter Configuring the Bootloader.
Verify that the “gpio-fan” was exported properly.
sh-phyboard-electra-am64xx-2:~# gpioinfo | grep gpio-fan line 40: unnamed output active-low consumer=gpio-fan
Toggling the Fan
Turn the fan ON.
sh-phyboard-electra-am64xx-2:~# echo 1 > /sys/class/thermal/cooling_device0/cur_state
Turn the fan OFF.
sh-phyboard-electra-am64xx-2:~# echo 0 > /sys/class/thermal/cooling_device0/cur_state
Enabling a proper Thermal Governor
If your application includes a GPIO-based fan, PHYTEC recommends enabling the bang-bang thermal governor as the default setting. This governor uses hysteresis to manage fan state transitions, preventing abrupt on/off cycling and enabling smoother control for fans that only support binary on/off operation, rather than variable speed throttling.
Update the current thermal governor strategy to bang-bang using the command below:
sh-phyboard-electra-am64xx-2:~# echo bang_bang > /sys/class/thermal/thermal_zone0/policy
Note
To enable the bang-bang thermal governor by default, recompile the kernel with CONFIG_THERMAL_DEFAULT_GOV_BANG_BANG=y in the menuconfig configuration. For further details, please refer to the guide: Modify The BSP.