Yes sure, the button are fully customizable...
Go into the TimeCore web interface, and in the "show control" tab.
Click on the "buttons" action list. Then in the "actions" column select "reset" and click "edit".
In the "task" list select the line "timecode/playstate/restart".
Now, in the "function" list, select "stop" instead of "restart".
That's it, you can close this window and the web interface, now the button will stop the timecode.
If you want you can put any action on this button, you can also change when the task is activates, for now it's when the button is pressed but it can also be when the button is released.
You can also change it to short press and then add an action that will be triggered when you do a long press.
Enjoy
