Example Baseboard Fan Control¶

Objective¶

The goal of this wiki page is to provide information on how to control the fan on the development kit, J7 on Baseboard and SoM Pin E3-4.

Information¶

The files that normally control the fan are located in /sys/class/hwmon/hwmon0. Information about this driver is available here.

On the development kit, the fan is either on (at 13000 rpm) or off.

The pre-built image for the development kit has the fan connected to the kernel's cpu cooling maps. (see Example_SOM_Temperature_Monitors for more information) In this mode, manual control of the fan is not really possible. You might try to turn it off but the kernel might just turn it right back on. If you want manual control, you will need to unhook the fan from the kernel's cpu cooling maps.

Electrical Info¶

• The AUXFAN_EN signal from the SoM Pin E3-4, connected to J7 on the development kit baseboard, is controlled by the PMIC O9039A385IZWSRQ1 (Ball A12 - GPIO_2) on the MitySOM-AM57x.
• The MitySoM AUXFAN_EN signal has a 10k pull-down resistor on the SoM.
• The AUXFAN_EN GPIO from the PMIC is referenced to the PMIC VCC1 input, which is SoM main input voltage, 5V.

For custom baseboard applications the AUXFAN_EN signal CANNOT be used to directly drive/power a Fan! It should only be used to control an external circuit that powers your fan, please see the reference circuit used on our development, snippet below: