remove tinyusb task to __empty() so that freerots can overwrite yield()

Author: LynnL4

cores/arduino/hooks.c

@@ -16,6 +16,7 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
+#include <stdint.h>
 /**
  * Empty yield() hook.
  *
@@ -25,23 +26,30 @@
  * Its defined as a weak symbol and it can be redefined to implement a
  * real cooperative scheduler.
  */
-static void __empty() {
-	// Empty
+extern void tud_task(void);
+extern uint32_t tud_cdc_n_write_flush (uint8_t itf);
+static void __empty()
+{
+// Empty
+#if defined(USE_TINYUSB)
+  tud_task();
+  tud_cdc_n_write_flush(0);
+#endif
 }
-
-void yield(void) __attribute__ ((weak, alias("__empty")));
+void yield(void) __attribute__((weak, alias("__empty")));
 
 /**
  * SysTick hook
  *
  * This function is called from SysTick handler, before the default
  * handler provided by Arduino.
  */
-static int __false() {
-	// Return false
-	return 0;
+static int __false()
+{
+  // Return false
+  return 0;
 }
-int sysTickHook(void) __attribute__ ((weak, alias("__false")));
+int sysTickHook(void) __attribute__((weak, alias("__false")));
 
 /**
  * SVC hook
@@ -50,10 +58,11 @@ int sysTickHook(void) __attribute__ ((weak, alias("__false")));
  * These functions are called from SVC handler, and PensSV handler.
  * Default action is halting.
  */
-static void __halt() {
-	// Halts
-	while (1)
-		;
+static void __halt()
+{
+  // Halts
+  while (1)
+    ;
 }
-void svcHook(void)    __attribute__ ((weak, alias("__halt")));
-void pendSVHook(void) __attribute__ ((weak, alias("__halt")));
+void svcHook(void) __attribute__((weak, alias("__halt")));
+void pendSVHook(void) __attribute__((weak, alias("__halt")));