Fan Interface

The Radxa Cubie A7S features an onboard fan interface. You can connect a fan using the 3-Pin fan interface to provide cooling for the motherboard.

Interface Location

For the specific location of the fan interface, please refer to the interface description section in the Hardware Interface tutorial!

Interface Specifications

Item	Specification
Interface Type	3-Pin Female Header
Pin Spacing	0.8mm
Arrangement	Single-row 3-pin
Installation Method	SMD, bottom-mount
Operating Voltage	5V (VCC5V0_SYS)
Speed Control	PWM (no tachometer feedback)

Pin Definition

Pin	Signal	Description
1	GND	Ground
2	PJ27_PWM1-9	PWM speed control signal
3	VCC5V0_SYS	5V power input

tip

Pay attention to the polarity when connecting the fan. The triangle silkscreen marking points to pin 1. Do not reverse the connection.

Usage Guide

Checking Fan Devices

1. Use the ls command to view the registered fan devices in the system.

radxa@device$

ls /sys/devices/platform/ | grep fan

Terminal will display output similar to:

radxa@device$

pwm-fan

• pwm-fan: Control device for the motherboard's built-in fan

2. Locate the PWM Control File

The fan's PWM control file is typically located in the /sys/class/hwmon/ directory. You need to find the hwmon directory corresponding to pwm-fan.

Use the ls command to view the PWM control files for the pwm-fan device.

radxa@device$

ls /sys/class/hwmon/

Terminal will display output similar to:

radxa@device$

hwmon0

3. Identify the Fan Control Node

Use the ls command to view the PWM control files for the pwm-fan device in the hwmon directory.

radxa@device$

ls -l /sys/class/hwmon/hwmon*/device

Terminal will display output similar to:

/sys/class/hwmon/hwmon0/device -> ../../../pwm-fan

Based on the terminal output, we can control pwm-fan through hwmon0.

Controlling Fan Speed

Use the echo command to set the fan speed. The PWM control range is typically 0~255 (0=stop, 255=full speed).

• Full Speed

radxa@device$

echo 255 | sudo tee /sys/class/hwmon/hwmon0/pwm1

• Half Speed

radxa@device$

echo 128 | sudo tee /sys/class/hwmon/hwmon0/pwm1

• Turn Off Fan

radxa@device$

echo 0 | sudo tee /sys/class/hwmon/hwmon0/pwm1

Interface Specifications

Technical Reference

For complete technical specifications and pin definitions, please refer to the Hardware Design: Schematic document in the download section.