Mute: toggle audio mute with SK2 short-tap, with LED + header indicator

Add a one-tap audio mute on the VFO and Channel screens:

- SK2 short-tap toggles mute via the built-in audioAmpMute()/audioAmpIsMuted().
  The tap is only consumed by the existing "set TX TG to incoming" behaviour
  while a DMR QSO is on screen, so mute works everywhere else.
- Header: a bold "M" is shown just left of the battery while muted (the
  firmware's built-in strike-through over the mode text also still shows).
- LED: flashes red for 0.5s every 2s while muted (main loop), overriding the
  normal RX/TX LED.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

MDUV380_firmware/application/include/user_interface/uiUtilities.h

@@ -243,6 +243,7 @@ void acceptPrivateCall(uint32_t id, int timeslot);
 bool rebuildVoicePromptOnExtraLongSK1(uiEvent_t *ev);
 bool repeatVoicePromptOnSK1(uiEvent_t *ev);
 bool handleMonitorMode(uiEvent_t *ev);
+void toggleAudioMute(void);
 void uiUtilityDisplayInformation(const char *str, displayInformation_t line, int8_t yOverride);
 void uiUtilityRenderQSODataAndUpdateScreen(void);
 

MDUV380_firmware/application/source/applicationMain.c

@@ -36,6 +36,7 @@
 #include "interfaces/adc.h"
 #include "interfaces/batteryRAM.h"
 #include "hardware/SPI_Flash.h"
+#include "io/Leds.h"
 #include "interfaces/adc.h"
 #include "hardware/radioHardwareInterface.h"
 
@@ -1432,6 +1433,27 @@ void applicationMainTask(void)
 			updateVolumeGain(currentMenu);
 		}
 
+		// Mute indicator: while muted, flash the RED LED for 0.5s every 2s.
+		// This overrides the normal RX/TX LED while muted.
+		{
+			static bool muteFlashActive = false;
+
+			if (audioAmpIsMuted())
+			{
+				bool flashOn = ((ticksGetMillis() % 2000) < 500);
+				LedWrite(LED_GREEN, 0);
+				LedWrite(LED_RED, (flashOn ? 1 : 0));
+				muteFlashActive = true;
+			}
+			else if (muteFlashActive)
+			{
+				// Just unmuted: release our forced LED state.
+				LedWrite(LED_RED, 0);
+				LedWrite(LED_GREEN, 0);
+				muteFlashActive = false;
+			}
+		}
+
 		while(ticksGetMillis() < startTime + 1)				// ensure this Task runs at 1ms intervals. Regardless of clock speed.
 		{
 			vTaskDelay(0U);

MDUV380_firmware/application/source/user_interface/uiChannelMode.c

@@ -1224,6 +1224,15 @@ static void handleEvent(uiEvent_t *ev)
 			return;
 		}
 
+		// SK2 short tap toggles audio mute. The DMR TG-set handler above consumes the
+		// tap (and returns) only while a QSO is on screen, so this won't fire then.
+		if (BUTTONCHECK_SHORTUP(ev, BUTTON_SK2) && (BUTTONCHECK_DOWN(ev, BUTTON_SK1) == 0) && (monitorModeData.isEnabled == false))
+		{
+			toggleAudioMute();
+			uiChannelModeUpdateScreen(0);
+			return;
+		}
+
 		// Display channel settings (RX/TX/etc) while SK1 is pressed
 		if ((uiDataGlobal.displayChannelSettings == false) && (monitorModeData.isEnabled == false) && BUTTONCHECK_DOWN(ev, BUTTON_SK1))
 		{

MDUV380_firmware/application/source/user_interface/uiUtilities.c

@@ -1852,6 +1852,14 @@ void uiUtilityRenderQSOData(void)
 	displayThemeResetToDefault();
 }
 
+// Toggle the audio mute (speaker) state. The header shows a mute icon and the LED
+// flashes amber (see the main loop) while muted.
+void toggleAudioMute(void)
+{
+	audioAmpMute(!audioAmpIsMuted());
+	headerRowIsDirty = true; // refresh the header so the mute icon appears/clears
+}
+
 void uiUtilityRenderHeader(bool isVFODualWatchScanning, bool isVFOSweepScanning, bool forceBatteryDisplay)
 {
 	const int MODE_TEXT_X_OFFSET = 1;
@@ -2176,6 +2184,14 @@ void uiUtilityRenderHeader(bool isVFODualWatchScanning, bool isVFOSweepScanning,
 	bool displayTime = (settingsIsOptionBitSet(BIT_DISPLAY_TIME_IN_HEADER) && (forceBatteryDisplay == false) && (batteryIsLow == false));
 #endif
 #endif
+	// Mute indicator: bold "M" just left of the battery indicator.
+	if (audioAmpIsMuted())
+	{
+		displayThemeApply(THEME_ITEM_FG_HEADER_TEXT, THEME_ITEM_BG_HEADER_TEXT);
+		displayPrintCore((DISPLAY_SIZE_X - 40), DISPLAY_Y_POS_HEADER, "M", FONT_SIZE_1_BOLD, TEXT_ALIGN_LEFT, false);
+		displayThemeResetToDefault();
+	}
+
 	// Display battery percentage/voltage
 	bool apoEnabled = (nonVolatileSettings.apo > 0);
 

MDUV380_firmware/application/source/user_interface/uiVFOMode.c

@@ -1161,6 +1161,15 @@ static void handleEvent(uiEvent_t *ev)
 			return;
 		}
 
+		// SK2 short tap toggles audio mute. The DMR TG-set handler above consumes the
+		// tap (and returns) only while a QSO is on screen, so this won't fire then.
+		if (BUTTONCHECK_SHORTUP(ev, BUTTON_SK2) && (BUTTONCHECK_DOWN(ev, BUTTON_SK1) == 0) && (monitorModeData.isEnabled == false))
+		{
+			toggleAudioMute();
+			uiVFOModeUpdateScreen(0);
+			return;
+		}
+
 		if ((uiVFOModeSweepScanning(true) == false) && (monitorModeData.isEnabled == false) && (uiDataGlobal.reverseRepeaterVFO == false) && (BUTTONCHECK_DOWN(ev, BUTTON_SK1) && BUTTONCHECK_DOWN(ev, BUTTON_SK2)))
 		{
 			int prevQSODisp = -1;