Fan working strategy

AIBOX-1684X fans work in 5 levels:

Main control current temperature	Fan working level
≥ 33℃	1
≥ 55℃	2
≥ 60℃	3
≥ 65℃	4
≥ 70℃	5

The higher the working level of the fan, the faster the speed. If the current temperature of the main controller is lower than 33°C, the fan is turned off by default.

Users can view the current working temperature of the main controller by executing the following command:

cat /sys/class/thermal/thermal_zone1/temp

For example the following is 45.5°C:

linaro@bm1684:~$ cat /sys/class/thermal/thermal_zone1/temp
45500

In addition, the user can also manually turn on the fan by himself (write 0-5, 0 is off, 5 is the maximum level):

sudo -i
echo 4 > /sys/class/thermal/cooling_device0/cur_state