diff --git a/NANOVNA_STM32_F303/board.h b/NANOVNA_STM32_F303/board.h
index 1962485..6c1432b 100644
--- a/NANOVNA_STM32_F303/board.h
+++ b/NANOVNA_STM32_F303/board.h
@@ -226,7 +226,7 @@
                                      PIN_ODR_HIGH(1) |             \
                                      PIN_ODR_HIGH(2) |         \
                                      PIN_ODR_HIGH(3) |         \
-                                     PIN_ODR_HIGH(GPIO_SD_DAT2) |             \
+                                     PIN_ODR_LOW(GPIO_SD_DAT2) |             \
                                      PIN_ODR_LOW(5) |              \
                                      PIN_ODR_HIGH(6) |             \
                                      PIN_ODR_HIGH(7) |             \
diff --git a/main.c b/main.c
index 04c4058..25591b5 100644
--- a/main.c
+++ b/main.c
@@ -2582,6 +2582,22 @@ void pwm_stop(void)
 #endif
 
 
+static uint16_t audio_mode = A_DAC;
+
+void set_audio_mode(uint16_t new_mode)
+{
+  if (new_mode == audio_mode)
+    return;
+  if (new_mode == A_PWM) {
+    DAC->CR&= ~DAC_CR_EN1; // Disable DAC CH1
+    pwm_init();
+  } else {
+    palSetPadMode(GPIOA, 4, PAL_MODE_INPUT);        // Back to DAC mode
+    DAC->CR|= DAC_CR_EN1 | DAC_CR_EN2; // Use DAC: CH1 and CH2
+  }
+  audio_mode = new_mode;
+}
+
 static const GPTConfig gpt4cfg = {
   8000000, // 8 MHz timer clock.
   NULL, // No callback
@@ -2699,19 +2715,18 @@ int main(void)
   spi_init();
   PULSE
 
-#ifdef __PWM__
-  pwm_init();
-  pwm_start(2000);
-  pwm_stop();
-#endif
+//#ifdef __PWM__
+//  pwm_init();
+//  pwm_start(2000);
+//  pwm_stop();
+//#endif
   /*
    * Set LCD display brightness (use DAC2 for control)
    * Starting DAC1 driver, setting up the output pin as analog as suggested by the Reference Manual.
    */
   dac_init();
   PULSE
-//  DAC->CR|= DAC_CR_EN1 | DAC_CR_EN2; // Use DAC: CH1 and CH2
-  DAC->CR|= DAC_CR_EN2; // Use DAC: CH1 and CH2
+  DAC->CR|= DAC_CR_EN1 | DAC_CR_EN2; // Use DAC: CH1 and CH2
   #ifdef  __LCD_BRIGHTNESS__
     lcd_setBrightness(DEFAULT_BRIGHTNESS);
   #endif
diff --git a/nanovna.h b/nanovna.h
index 1959ce0..c30bc4e 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -344,6 +344,14 @@ extern const char * const info_about[];
 #ifdef TINYSA4
 void toggle_extra_lna(void);
 void set_extra_lna(int t);
+
+enum { A_DAC, A_PWM };
+void set_audio_mode(uint16_t new_mode);
+void pwm_start(int f);
+void pwm_stop(void);
+#ifdef __GUARD__
+void reset_guard(void);
+#endif
 #endif
 
 // ------------------------------- sa_core.c ----------------------------------
@@ -1747,8 +1755,9 @@ void interpolate_maximum(int m);
 void calibrate_modulation(int modulation, int8_t *correction);
 
 enum {
-  M_OFF, M_IMD, M_OIP3, M_PHASE_NOISE, M_SNR, M_PASS_BAND, M_LINEARITY, M_AM, M_FM, M_THD, M_CP, M_NF_TINYSA, M_NF_STORE, M_NF_VALIDATE, M_NF_AMPLIFIER, M_GUARD, M_DECONV
+  M_OFF, M_IMD, M_OIP3, M_PHASE_NOISE, M_SNR, M_PASS_BAND, M_LINEARITY, M_AM, M_FM, M_THD, M_CP, M_NF_TINYSA, M_NF_STORE, M_NF_VALIDATE, M_NF_AMPLIFIER, M_GUARD, M_DECONV,M_MAX
 };
+#define MEASUREMENT_TEXT "OFF","IMD","OIP3","PN","SNR","PASS","LIN","AM","FM","THD","CP","NF T","NF S","NF V","NF A","GUARD","DECONF"
 
 enum {
   T_AUTO, T_NORMAL, T_SINGLE, T_DONE, T_UP, T_DOWN, T_MODE, T_PRE, T_POST, T_MID
diff --git a/sa_core.c b/sa_core.c
index c0c972f..4456562 100644
--- a/sa_core.c
+++ b/sa_core.c
@@ -4787,6 +4787,13 @@ again:                                                              // Spur redu
 
 static uint8_t low_count = 0;
 static uint8_t sweep_counter = 0;           // Only used for HW refresh
+#ifdef __GUARD__
+static int last_guard = -1;
+
+void reset_guard(void) {
+  last_guard = -1;
+}
+#endif
 
 // main loop for measurement
 static bool sweep(bool break_on_operation)
@@ -4873,17 +4880,19 @@ static bool sweep(bool break_on_operation)
         current_guard = 0;
     }
     while(!(setting.guards[current_guard].enabled));
-    if (setting.guards[current_guard].end > setting.guards[current_guard].start) {
+    if (setting.guards[current_guard].end > setting.guards[current_guard].start && last_guard != current_guard) {
+      last_guard = current_guard;
       set_sweep_frequency(ST_START, setting.guards[current_guard].start);
       set_sweep_frequency(ST_STOP, setting.guards[current_guard].end);
       set_rbw(8000);
       set_sweep_points((setting.guards[current_guard].end - setting.guards[current_guard].start) / 800000);
     }
-    pwm_init();
+    set_audio_mode(A_PWM);
     pwm_stop();
+  } else {
+    last_guard = -1;
+    set_audio_mode(A_DAC);
   }
-  else
-    palSetPadMode(GPIOA, 4, PAL_MODE_INPUT);        // Back to DAC mode
 #endif
 
   setting.measure_sweep_time_us = 0;                   // start measure sweep time
diff --git a/ui.c b/ui.c
index 0bf17fe..6e1bb98 100644
--- a/ui.c
+++ b/ui.c
@@ -1497,6 +1497,9 @@ static const menuitem_t  menu_settings2[];
 static const menuitem_t  menu_lowoutput_settings[];
 extern bool dirty;
 char range_text[20];
+#ifdef TINYSA4
+const char * const measurement_text[] = {MEASUREMENT_TEXT};
+#endif
 
 #ifdef TINYSA4
 int input_is_calibrated(void)
@@ -3190,6 +3193,7 @@ static UI_FUNCTION_ADV_CALLBACK(menu_guard_select_acb)
     if (count == 0) setting.guards[0].enabled = true;
     b->icon = (setting.guards[data].enabled?BUTTON_ICON_CHECK:BUTTON_ICON_NOCHECK) ;
     plot_printf(b->text, sizeof(b->text), "%.6FHz\n%.6FHz", (float)setting.guards[data].start, (float)setting.guards[data].end);
+    reset_guard();
     return;
   }
   active_guard = data;
@@ -5540,6 +5544,14 @@ redraw_cal_status:
   quick_menu_y[max_quick_menu] = y;
   quick_menu[max_quick_menu++] = (menuitem_t *)NULL;
 
+#ifdef TINYSA4
+  if (setting.measurement != M_OFF){
+    ili9341_set_foreground(LCD_BRIGHT_COLOR_GREEN);
+    lcd_printf(x, y, measurement_text[setting.measurement]);
+    y += 2*YSTEP + YSTEP/2;
+  }
+
+#endif
 //  if (setting.mode == M_LOW) {
     // Attenuation
     ili9341_set_foreground(setting.auto_attenuation ? LCD_FG_COLOR : LCD_BRIGHT_COLOR_GREEN);