diff --git a/main.c b/main.c
index 07821cb..424b80c 100644
--- a/main.c
+++ b/main.c
@@ -615,7 +615,16 @@ int16_t dump_buffer[AUDIO_BUFFER_LEN];
 int16_t dump_selection = 0;
 #endif
 
-volatile int16_t wait_count = 0;
+volatile uint8_t wait_count = 0;
+volatile uint8_t accumerate_count = 0;
+
+const int8_t bandwidth_accumerate_count[] = {
+  1, // 1kHz
+  3, // 300Hz
+  10, // 100Hz
+  33, // 30Hz
+  100 // 10Hz
+};
 
 float measured[2][POINTS_COUNT][2];
 #endif
@@ -643,13 +652,16 @@ void i2s_end_callback(I2SDriver *i2sp, size_t offset, size_t n)
   (void)i2sp;
   (void)n;
 
-  if (wait_count > 0) {
-    if (wait_count == 1) 
+  if (wait_count > 1) {
+    --wait_count;
+  } else if (wait_count > 0) {
+    if (accumerate_count > 0) {
       dsp_process(p, n);
+      accumerate_count--;
+    }
 #ifdef ENABLED_DUMP
-      duplicate_buffer_to_dump(p);
+    duplicate_buffer_to_dump(p);
 #endif
-    --wait_count;
   }
 
 #if PORT_SUPPORTS_RT
@@ -871,20 +883,20 @@ bool sweep(bool break_on_operation)
     if (frequencies[i] == 0) break;
     delay = set_frequency(frequencies[i]);     // 700
     tlv320aic3204_select(0);                   // 60 CH0:REFLECT, reset and begin measure
-    DSP_START(delay + ((i == 0) ? 1 : 0));     // 1900
+    dsp_start(delay + ((i == 0) ? 1 : 0));     // 1900
     //================================================
     // Place some code thats need execute while delay
     //================================================
-    DSP_WAIT_READY;
+    dsp_wait();
     // calculate reflection coefficient
     (*sample_func)(measured[0][i]);            // 60
 
     tlv320aic3204_select(1);                   // 60 CH1:TRANSMISSION, reset and begin measure
-    DSP_START(DELAY_CHANNEL_CHANGE);           // 1700
+    dsp_start(DELAY_CHANNEL_CHANGE);           // 1700
     //================================================
     // Place some code thats need execute while delay
     //================================================
-    DSP_WAIT_READY;
+    dsp_wait();
     // calculate transmission coefficient
     (*sample_func)(measured[1][i]);            // 60
                                                // ======== 170 ===========
diff --git a/nanovna.h b/nanovna.h
index fd0eefc..276df10 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -473,6 +473,7 @@ typedef struct properties {
 #ifdef __VNA__
   uint8_t _domain_mode; /* 0bxxxxxffm : where ff: TD_FUNC m: DOMAIN_MODE */
   uint8_t _marker_smith_format;
+  uint8_t _bandwidth;
 #endif  
   uint8_t _reserved[2];
   uint32_t checksum;
@@ -507,6 +508,7 @@ extern properties_t current_props;
 #define domain_mode current_props._domain_mode
 #define velocity_factor current_props._velocity_factor
 #define marker_smith_format current_props._marker_smith_format
+#define bandwidth current_props._bandwidth
 #endif
 
 #define FREQ_IS_STARTSTOP() (!(config.freq_mode&FREQ_MODE_CENTER_SPAN))
diff --git a/ui.c b/ui.c
index f89aca6..544d47b 100644
--- a/ui.c
+++ b/ui.c
@@ -637,6 +637,14 @@ menu_transform_filter_cb(int item, uint8_t data)
   domain_mode = (domain_mode & ~TD_FUNC) | data;
   ui_mode_normal();
 }
+
+static void
+menu_bandwidth_cb(int item)
+{
+  bandwidth = item;
+  draw_menu();
+}
+
 static void 
 choose_active_marker(void)
 {
@@ -940,12 +948,23 @@ const menuitem_t menu_transform[] = {
   { MT_NONE, 0, NULL, NULL } // sentinel
 };
 
+const menuitem_t menu_bandwidth[] = {
+  { MT_CALLBACK, 0, "1 kHz", menu_bandwidth_cb },
+  { MT_CALLBACK, 0, "300 Hz", menu_bandwidth_cb },
+  { MT_CALLBACK, 0, "100 Hz", menu_bandwidth_cb },
+  { MT_CALLBACK, 0, "30 Hz", menu_bandwidth_cb },
+  { MT_CALLBACK, 0, "10 Hz", menu_bandwidth_cb },
+  { MT_CANCEL, 0, S_LARROW" BACK", NULL },
+  { MT_NONE, 0, NULL, NULL } // sentinel
+};
+
 const menuitem_t menu_display[] = {
   { MT_SUBMENU, 0, "TRACE", menu_trace },
   { MT_SUBMENU, 0, "FORMAT", menu_format },
   { MT_SUBMENU, 0, "SCALE", menu_scale },
   { MT_SUBMENU, 0, "CHANNEL", menu_channel },
   { MT_SUBMENU, 0, "TRANSFORM", menu_transform },
+  { MT_SUBMENU, 0, "BANDWIDTH", menu_bandwidth },  
   { MT_CANCEL, 0, S_LARROW" BACK", NULL },
   { MT_NONE, 0, NULL, NULL } // sentinel
 };
@@ -1400,6 +1419,11 @@ menu_item_modify_attribute(const menuitem_t *menu, int item,
       *bg = DEFAULT_MENU_TEXT_COLOR;
       *fg = config.menu_normal_color;
     }
+  } else if (menu == menu_bandwidth) {
+      if (item == bandwidth) {
+        *bg = 0x0000;
+        *fg = 0xffff;
+      }
   } else if (menu == menu_transform) {
       if ((item == 0 && (domain_mode & DOMAIN_MODE) == DOMAIN_TIME)
        || (item == 1 && (domain_mode & TD_FUNC) == TD_FUNC_LOWPASS_IMPULSE)