[usb] Enable the USB core on calculator plugged.

Change-Id: I5b8ab068936524e775bb77a4569a2601e5a9844a

apps/usb_timer.cpp

@@ -12,6 +12,9 @@ USBTimer::USBTimer(AppsContainer * container) :
 bool USBTimer::fire() {
   bool needRedrawing = false;
   if (Ion::USB::isPlugged()) {
+    if (!m_previousPluggedState) {
+      Ion::USB::removeSoftDisconnect();
+    }
     if (!m_previousPluggedState && GlobalPreferences::sharedGlobalPreferences()->examMode() == GlobalPreferences::ExamMode::Activate) {
       m_container->displayExamModePopUp(false);
       needRedrawing = true;

ion/include/ion/usb.h

@@ -5,6 +5,7 @@ namespace Ion {
 namespace USB {
 
 bool isPlugged();
+void removeSoftDisconnect();
 void DFU();
 
 }

ion/src/device/usb.cpp

@@ -13,6 +13,10 @@ bool isPlugged() {
   return Device::VbusPin.group().IDR()->get(Device::VbusPin.pin());
 }
 
+void removeSoftDisconnect() {
+  OTG.DCTL()->setSDIS(false);
+}
+
 }
 }
 

ion/src/shared/dummy/usb.cpp

@@ -4,5 +4,8 @@ bool Ion::USB::isPlugged() {
   return false;
 }
 
+void Ion::USB::removeSoftDisconnect() {
+}
+
 void Ion::USB::DFU() {
 }