Fix mixer scheduler 33Hz only issue

introduced by opentx/opentx#8474

radio/src/mixer_scheduler.cpp

@@ -68,9 +68,13 @@ void mixerSchedulerSetPeriod(uint8_t moduleIdx, uint16_t periodUs)
   mixerSchedules[moduleIdx].period = periodUs;
 }
 
-bool mixerSchedulerWaitForTrigger(uint8_t timeoutMs)
+void mixerSchedulerClearTrigger()
 {
   RTOS_CLEAR_FLAG(mixerFlag);
+}
+
+bool mixerSchedulerWaitForTrigger(uint8_t timeoutMs)
+{
   return RTOS_WAIT_FLAG(mixerFlag, timeoutMs);
 }
 

radio/src/mixer_scheduler.h

@@ -43,6 +43,9 @@ void mixerSchedulerResetTimer();
 // Set the scheduling period for a given module
 void mixerSchedulerSetPeriod(uint8_t moduleIdx, uint16_t periodUs);
 
+// Clear the flag before waiting
+void mixerSchedulerClearTrigger();
+
 // Wait for the scheduler timer to trigger
 // returns true if timeout, false otherwise
 bool mixerSchedulerWaitForTrigger(uint8_t timeoutMs);
@@ -66,6 +69,7 @@ void mixerSchedulerISRTrigger();
 #define mixerSchedulerStop()
 #define mixerSchedulerResetTimer()
 #define mixerSchedulerSetPeriod(m,p)
+#define mixerSchedulerClearTrigger()
 
 static inline bool mixerSchedulerWaitForTrigger(uint8_t timeout)
 {

radio/src/tasks.cpp

@@ -140,11 +140,19 @@ TASK_FUNCTION(mixerTask)
   mixerSchedulerStart();
 #endif
 
+  // clear the flag before first loop
+  mixerSchedulerClearTrigger();
+
   while (true) {
-    for (int timeout = 0; timeout < MIXER_MAX_PERIOD; timeout += MIXER_FREQUENT_ACTIONS_PERIOD) {
-      bool interruptedByTimeout = mixerSchedulerWaitForTrigger(MIXER_FREQUENT_ACTIONS_PERIOD);
+    int timeout = 0;
+    for (; timeout < MIXER_MAX_PERIOD; timeout += MIXER_FREQUENT_ACTIONS_PERIOD) {
+
+      // run periodicals before waiting for the trigger
+      // to keep the delay short
       execMixerFrequentActions();
-      if (!interruptedByTimeout) {
+
+      // mixer flag triggered?
+      if (!mixerSchedulerWaitForTrigger(MIXER_FREQUENT_ACTIONS_PERIOD)) {
         break;
       }
     }
@@ -155,6 +163,9 @@ TASK_FUNCTION(mixerTask)
 #endif
 
 #if !defined(PCBSKY9X)
+    // clear the flag ASAP to avoid missing a tick
+    mixerSchedulerClearTrigger();
+
     // re-enable trigger
     mixerSchedulerEnableTrigger();
 #endif