Fan control balenaBlock

This block can be used to controls a cooling fan based on a system thermal zones (temperature measurement managed on Linux systems).

The block supports 2 types of fan control strategies:

• GPIO based ON/OFF control, with an hysteresis,
• PWM based control, with speed slopes.

NOTE: As linux kernel manages temperatures in Celsius, all temperatures in this block configuration are in Celsius (and integer value).

Compatibility

The primary role for this block is to allow for CPU fan control by user-space software, which is easier to re-configure on the fly than kernel based fan control, and thus more suitable for hacking projects.

As long as your senors appear in /sys/class/thermal/ as a thermalzone, and the GPIO/PWM you want to use is not in use by other configuration, this block should be compatible.

Configuration

The block is configured through environment variables passed to the service. Available variables are:

• For GPIO mode:

  • FAN_GPIO: The GPIO number your fan is connected to, see your specific board reference to get this number (default value 132),
  • THERMAL_HIGH: The "high" temperature, the fan will turn ON when temperature reaches this level (default value 60),
  • THERMAL_LOW: The "low" temperature, the fan will turn OFF when temperature reaches this level (default value 40).

• For PWM mode:

  • PWM: a comma-separated address of the PWMCHIP/PWM to use. e.g. 1,0 will use /sys/class/pwm/pwmchip1/pwm to control the PWM (no default value, setting this value disables GPIO mode and enables PWM mode),
  • PWM_PERIOD: period to configure your pwmX/period to, this will be the maximum value of your duty cycle. (default is 40000),
  • PWM_TEMPS: a comma-separated list of configuration temperature points.These points are used for linear interpolation for the PWM control curve (default 0,40,50,70).
  • PWM_DUTY: a comma-separated list of duty-cycles to apply for each of previously defined temperature points. This list should be the same length as PWM_TEMPS, with each value in the range 0-PWM_PERIOD. (default 0,200,10000,40000).

• For both modes:

  • REFRESH_DELAY: the period, in seconds, between two fan speed update (default value 60),
  • THERMAL_ZONE: the thermal zone device number on your system you want to use as a source for fan control (default value 0).

Additional configuration

You also will need to set your service as privileged and enable io.balena.features.sysfs=1 in your labels.

Example configuration in GPIO mode

services:
  fan-control:
      image: bh.cr/balena/fan_control_arm
      privileged: true
      restart: always
      labels:
         io.balena.features.sysfs: 1
      environment:
         - 'REFRESH_DELAY=30'
         - 'GPIO="14"'
         - 'THERMAL_ZONE=0'
         - 'THERMAL_LOW=45'
    		 - 'THERMAL_HIGH=65'

Example configuration in PWM mode

services:
  fan-control:
      image: bh.cr/balena/fan_control_arm
      privileged: true
      restart: always
      labels:
         io.balena.features.sysfs: 1
      environment:
         - 'THERMAL_ZONE=1'
         - 'REFRESH_DELAY=10'
         - 'PWM="1,0"'
         - 'PWM_TEMPS="0,40,50,70"'
         - 'PWM_DUTY="0,100,1000,40000"'