[Taranis] Pull request #610 - Speaker volume hysteresis

radio/src/opentx.cpp

@@ -3035,8 +3035,10 @@ uint8_t mSwitchDuration[1+NUM_ROTARY_ENCODERS] = { 0 };
 #endif
 
 #if defined(CPUARM)
+#define VOLUME_HYSTERESIS 10		// how much must a input value change to actually be considered for new volume setting
 uint8_t currentSpeakerVolume = 255;
 uint8_t requiredSpeakerVolume;
+getvalue_t requiredSpeakerVolumeRawLast = 1024 + 1; //initial value must be outside normal range
 uint8_t fnSwitchDuration[NUM_CFN] = { 0 };
 
 inline void playCustomFunctionFile(CustomFnData *sd, uint8_t id)
@@ -3262,7 +3264,12 @@ void evalFunctions()
         }
         else if (CFN_FUNC(sd) == FUNC_VOLUME) {
           if (CFN_ACTIVE(sd)) {
-            requiredSpeakerVolume = ((1024 + getValue(CFN_PARAM(sd))) * VOLUME_LEVEL_MAX) / 2048;
+            getvalue_t raw = getValue(CFN_PARAM(sd));
+            //only set volume if input changed more than hysteresis
+            if (abs(requiredSpeakerVolumeRawLast - raw) > VOLUME_HYSTERESIS) {
+              requiredSpeakerVolumeRawLast = raw;
+            }
+	    requiredSpeakerVolume = ((1024 + requiredSpeakerVolumeRawLast) * VOLUME_LEVEL_MAX) / 2048;
           }
           else {
             active = false;