Where is the reset switch on XStick ?

I loaded the Router Sensor firmware on a XStick. Now, I want to change the firmware on it. But, when I tried to do it, X-CTU asked me to “Press and release Reset switch”. But there is no Reset switch on a XStick. How can I change the firmware on the XStick without it ?

I answer my question : to reset a Xstick, you have to connect the pin 13 of the EM250 SoC to the ground when X-CTU asks to reset it.