From 3e2e665955e2d25c4f321460422c84f9773da2be Mon Sep 17 00:00:00 2001
From: Bertrand Songis <bsongis@gmail.com>
Date: Sat, 1 Feb 2014 21:44:02 +0100
Subject: [PATCH] [Taranis] Pull request #610 - Speaker volume hysteresis

---
 radio/src/opentx.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/radio/src/opentx.cpp b/radio/src/opentx.cpp
index b1d0ef3b0..ff3729fae 100644
--- a/radio/src/opentx.cpp
+++ b/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;