fix esp32 build with examples

Author: hathach

examples/DualRole/HID/hid_mouse_tremor_filter/hid_mouse_tremor_filter.ino

@@ -168,7 +168,6 @@ butterworth_coeffs_t butterworth_lowpass(float cutoff_frequency, float sampling_
   butterworth_coeffs_t coe;
 
   float omega = 2.0 * PI * cutoff_frequency / sampling_frequency;
-  float c = cos(omega);
   float s = sin(omega);
   float t = tan(omega / 2.0);
   float alpha = s / (2.0 * t);

examples/DualRole/MassStorage/msc_data_logger/msc_data_logger.ino

@@ -93,17 +93,20 @@ void data_log(void) {
 }
 
 #ifdef USE_FREERTOS
+
+#ifdef ARDUINO_ARCH_ESP32
+  #define USBH_STACK_SZ 2048
+#else
+  #define USBH_STACK_SZ 200
+#endif
+
 void usbhost_rtos_task(void *param) {
   (void) param;
   while (1) {
     USBHost.task();
   }
 }
 
-void create_usbhost_rtos_task(void) {
-  const uint32_t usbh_stack_size = 400;
-  xTaskCreate(usbhost_rtos_task, "usbh", usbh_stack_size, NULL, TASK_PRIO_HIGH, NULL);
-}
 #endif
 
 void setup() {
@@ -118,7 +121,8 @@ void setup() {
 #endif
 
 #ifdef USE_FREERTOS
-  create_usbhost_rtos_task();
+  // Create a task to run USBHost.task() in background
+  xTaskCreate(usbhost_rtos_task, "usbh", USBH_STACK_SZ, NULL, 3, NULL);
 #endif
 
 //  while ( !Serial ) delay(10);   // wait for native usb