Stop using 50ms mixer period when no module enabled

Also adds a 2ms mixer period if internal and external modules are stopped
but joystick mode is active

radio/src/mixer_scheduler.cpp

@@ -45,6 +45,11 @@ uint16_t getMixerSchedulerPeriod()
   if (mixerSchedules[EXTERNAL_MODULE].period) {
     return mixerSchedules[EXTERNAL_MODULE].period;
   }
+#endif
+#if defined(STM32) && !defined(SIMU)
+  if (getSelectedUsbMode() == USB_JOYSTICK_MODE) {
+    return MIXER_SCHEDULER_JOYSTICK_PERIOD_US;
+  }
 #endif
   return MIXER_SCHEDULER_DEFAULT_PERIOD_US;
 }

radio/src/mixer_scheduler.h

@@ -21,7 +21,8 @@
 #ifndef _MIXER_SCHEDULER_H_
 #define _MIXER_SCHEDULER_H_
 
-#define MIXER_SCHEDULER_DEFAULT_PERIOD_US 4000u // 4ms
+#define MIXER_SCHEDULER_DEFAULT_PERIOD_US  4000u // 4ms
+#define MIXER_SCHEDULER_JOYSTICK_PERIOD_US 2000u // 2ms
 
 #define MIN_REFRESH_RATE      1750 /* us */
 #define MAX_REFRESH_RATE     50000 /* us */

radio/src/pulses/pulses.cpp

@@ -327,8 +327,8 @@ void enablePulsesExternalModule(uint8_t protocol)
 #endif
 
     default:
-      // external module stopped, set period to 50ms (necessary for USB Joystick, for instance)
-      mixerSchedulerSetPeriod(EXTERNAL_MODULE, 50000/*us*/);
+      // external module stopped, use default mixer period
+      mixerSchedulerSetPeriod(EXTERNAL_MODULE, 0);
       break;
   }
 }
@@ -500,7 +500,7 @@ static void enablePulsesInternalModule(uint8_t protocol)
 #endif
 
     default:
-      // internal module stopped, set internal period to 0 and start the scheduler
+      // internal module stopped, use default mixer period
       mixerSchedulerSetPeriod(INTERNAL_MODULE, 0);
       break;
   }