Initial version of new code for layer switch is added.

common/timer.c

@@ -22,6 +22,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
 // counter resolution 1ms
+// NOTE: union { uint32_t timer32; struct { uint16_t dummy; uint16_t timer16; }}
 volatile uint32_t timer_count = 0;
 
 void timer_init(void)