Updated the Odroid U3 to the latest version of odroid-3.19.y (# git clone -b odroid-3.19.y –single-branch https://github.com/tobiasjakobi/linux-odroid ).

After checking that all the pwm-fan and temperature options were selected in the kernel config, I set ‘Default Thermal governor‘ to ‘step-wise‘.

After compiling/installing, I tried some more tests:

Using ‘stress’ to raise the temperature:

# stress --cpu 4 --timeout 60
stress: info: [2842] dispatching hogs: 4 cpu, 0 io, 0 vm, 0 hdd

– after around 30 seconds, the temperature is above the 70 degree mark, and the fan starts..

When stress finishes, temperature drops to around 65, and the fan stops..

[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
69000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
70000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
71000
<<< fan starts >>>
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
71000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
71000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
71000
.....................
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
70000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
70000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
70000
<< stress stops >>>
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
71000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
70000
....................
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
65000
<< fan stops >>
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
63000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
60000
[root@rgodroid rgadsdon]# cat /sys/devices/virtual/thermal/thermal_zone0/temp
60000

So now the fan is ‘automatic’, without the need for any external programs..

Thanks to tobiasjakobi for his help with this, and porting the latest (v6) patches to odroid-3.19.y.

Robert Gadsdon.   February 15, 2015.