[ion] Add Ion::usleep

Change-Id: Ife70133410e55c3f0af9a838543042a3da618119

ion/include/ion.h

@@ -20,6 +20,7 @@ void ion_app();
 namespace Ion {
 
 void msleep(long ms);
+void usleep(long us);
 
 /* CAUTION: This is a complete reset! */
 void reset();

ion/src/device/device.cpp

@@ -19,6 +19,11 @@ void Ion::msleep(long ms) {
       __asm volatile("nop");
   }
 }
+void Ion::usleep(long us) {
+  for (volatile long i=0; i<us; i++) {
+    __asm volatile("nop");
+  }
+}
 
 void Ion::reset() {
   CM4.AIRCR()->requestReset();

ion/src/simulator/init.cpp

@@ -63,7 +63,7 @@ bool Ion::Keyboard::keyDown(Ion::Keyboard::Key key) {
 }
 
 void Ion::msleep(long ms) {
-  usleep(1000*ms);
+  ::usleep(1000*ms);
   sDisplay->redraw();
   Fl::wait();
 }