Fan

The phyCORE-AM64x development kit provides fan connectivity via a 4-pin Hirose connector at X12 (VCC_5V0_SW rail). The fan is intended to be mounted directly to the processor heat sink for thermal management. The regulated 5V output is enabled by driving GPIO0_28 low (0), turning the fan on. When GPIO0_28 is pulled high (1), the 5V supplied to the fan connector will be turned off. This guide will demonstrate how to test your connections to the header x12. To learn more information about the phyCORE-AM64x thermal management and fan utilization, please see section 4.9 in the Hardware Manual.

phyCORE-AM64x Fan Location

Requirements

The phyCORE-AM64x development kit does not include a heat sink and fan. The below is the fan tested on the PHYTEC hardware:

Item

Description

Link

Heat Sink

(29mmx29mmx9.5mm)

Digikey link (heat sink)

Fan

DC axial fan, 30mm square x 10mm

Digikey link (fan)

Female Connector

4 pin keyed header

Digikey link (female connector)

Crimping Terminals

4x crimping jackets

Mouser link
phyCORE-AM64x (1566.1) Fan Schematic

Connecting Your Fan

  • Connect fan to the 4-pin Hirose connector located at X12.

    phyCORE-AM64x Fan Pin 1 Location

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.

    Target (U-boot)
    setenv overlays k3-am64-phyboard-electra-gpio-fan.dtbo
boot

Note

For more information about overlays see chapter Configuring the Bootloader.

  • Verify that the “gpio-fan” was exported properly to gpio-453.

    Target (Linux)
    cat /sys/kernel/debug/gpio
    Expected Output
     root@phyboard-electra-am64xx-2:~# cat /sys/kernel/debug/gpio
 gpiochip1: GPIOs 337-424, parent: platform/601000.gpio, 601000.gpio:
 gpio-355 (                    |PHY reset           ) out lo ACTIVE LOW
 gpio-356 (                    |PHY reset           ) out lo ACTIVE LOW
 gpio-379 (                    |wp                  ) out lo
 gpio-380 (                    |spi1 CS1            ) out lo ACTIVE LOW

 gpiochip0: GPIOs 425-511, parent: platform/600000.gpio, 600000.gpio:
 gpio-437 (                    |green:heartbeat     ) out lo
 gpio-440 (                    |red:disk            ) out lo
 gpio-441 (                    |green:disk          ) out lo
 gpio-442 (                    |home                ) in  lo
 gpio-446 (                    |menu                ) in  lo
 gpio-453 (                    |gpio-fan            ) out lo ACTIVE LOW
 gpio-457 (                    |standby             ) out lo
 gpio-460 (                    |standby             ) out lo
 gpio-488 (                    |PHY reset           ) out lo ACTIVE LOW

Toggling the Fan

  • Turn the fan ON.

    Target (Linux)
    echo 1 > /sys/class/thermal/cooling_device0/cur_state

Note

Run the command above 3-4 times to have the fan stay ON consistently.

  • Turn the fan OFF.

    Target (Linux)
    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:

Target (Linux)
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.