diff --git a/MilliOhmMeter_FW/platformio.ini b/MilliOhmMeter_FW/platformio.ini
index e3276b5..b00ef8f 100644
--- a/MilliOhmMeter_FW/platformio.ini
+++ b/MilliOhmMeter_FW/platformio.ini
@@ -17,5 +17,6 @@ lib_ldf_mode = deep+
 lib_deps = 
 	adafruit/Adafruit ADS1X15@^2.2.0
 	robtillaart/RunningAverage@^0.4.2
+	fabianoriccardi/Melody Player@^2.2.2
 build_flags = 
 	-DCORE_DEBUG_LEVEL=3
diff --git a/MilliOhmMeter_FW/src/board.cpp b/MilliOhmMeter_FW/src/board.cpp
index 4af3428..ba9d3fb 100644
--- a/MilliOhmMeter_FW/src/board.cpp
+++ b/MilliOhmMeter_FW/src/board.cpp
@@ -5,7 +5,7 @@ void initSerial(void)
 {
   Serial.begin(115200);
   Serial.flush();
-  delay(2000);
+  delay(500);
   log_i("Init serial: OK");
 }
 
diff --git a/MilliOhmMeter_FW/src/gain_control.cpp b/MilliOhmMeter_FW/src/gain_control.cpp
index 67e4d0c..bd9322b 100644
--- a/MilliOhmMeter_FW/src/gain_control.cpp
+++ b/MilliOhmMeter_FW/src/gain_control.cpp
@@ -9,15 +9,17 @@ c_gainControl mode1000mA(e_measureMode::mA1000, 0, 1, 0, 0, 0, 1); //warning not
 //UC02 > G=1 (met JP5naar 1000mA); UC03 > G=5(met JP7 naar 200mA); UC04 > G=50 (@20mA); UC05 > 1000mA; UC06 > 200mA. Current: niets gekozen = 20mA.
 
 
-std::vector<c_gainControl> gainList;
+std::vector<c_gainControl*> gainList;
 
 e_measureMode lastGain = e_measureMode::mA20;
 
 void initGainControl(void)
 {
-  gainList.push_back(mode20mA);
-  gainList.push_back(mode200mA);
-  gainList.push_back(mode1000mA);
+  gainList.push_back(&mode20mA);
+  gainList.push_back(&mode200mA);
+  gainList.push_back(&mode1000mA);
+
+  mode20mA.activate();
 }
 
 bool setGain(e_measureMode mode)
@@ -30,9 +32,9 @@ bool setGain(e_measureMode mode)
   
   for (auto &&gain : gainList)
   {
-    if (gain.getMode() == mode)
+    if (gain->getMode() == mode)
     {
-      gain.activate();
+      gain->activate();
       found = true;
       lastGain = mode;
       log_i("set new gain %d", mode);
@@ -52,7 +54,7 @@ void resetGain(void)
   log_d("reset gain control");
   for (auto &&gain : gainList)
   {
-    gain.deactivate();
+    gain->deactivate();
   }
   setGain(mA20);
 }
\ No newline at end of file
diff --git a/MilliOhmMeter_FW/src/main.cpp b/MilliOhmMeter_FW/src/main.cpp
index 14632f2..1170bdd 100644
--- a/MilliOhmMeter_FW/src/main.cpp
+++ b/MilliOhmMeter_FW/src/main.cpp
@@ -4,6 +4,7 @@
 #include "buttons.h"
 #include "display.h"
 #include "gain_control.h"
+#include "tone_hall.hpp"
 
 uint64_t looptime = 0;
 
@@ -12,6 +13,7 @@ void setup()
   initBoard();
   initGainControl();
   initMeasure();
+  //initTone();
   initMeasureMode();
   initDisplay();
   looptime = millis();
@@ -22,6 +24,7 @@ void loop()
   // put your main code here, to run repeatedly:
   looptime = micros();
   handleMeasure();
+  //handleTone();
   handleDisplay();
   setTimer((double)(micros() - looptime)/1000);
   log_d("T=%4.2fms\n", (double)(micros() - looptime)/1000);
diff --git a/MilliOhmMeter_FW/src/screen_main.cpp b/MilliOhmMeter_FW/src/screen_main.cpp
index 9e5051d..3f6d23a 100644
--- a/MilliOhmMeter_FW/src/screen_main.cpp
+++ b/MilliOhmMeter_FW/src/screen_main.cpp
@@ -113,9 +113,9 @@ void screenMainDrawLayout(void)
   drawDashedHLine(0, 12, 220);
   drawDashedVLine(40, 12, 33);
   getDisplay()->setFont(FONT8);
-  uint16_t rate = float(1 / getSampleRate());
+  float rate = getSampleRate();
   getDisplay()->setCursor(5, 8);
-  getDisplay()->printf("Fs:%dHz", rate);
+  getDisplay()->printf("Fs:%4.0fHz", rate);
   getDisplay()->setCursor(170, 8);
   getDisplay()->printf("loop=%dms", timer);
 }
@@ -127,7 +127,7 @@ void ScreenMainDrawValues(void)
   getDisplay()->printf("%4.3f", getValue());
   uint16_t stringwidth = getDisplay()->getStrWidth(drawValue("", getValue(), "").c_str());
   getDisplay()->setFont(u8g2_font_8x13_t_symbols);
-  getDisplay()->drawUTF8(78 + stringwidth + 3, 43, "Ω");
+  getDisplay()->drawUTF8(78 + stringwidth + 4, 43, "Ω");
   getDisplay()->setFont(FONT8);
   // getDisplay()->drawUTF8(60 + stringwidth + 3, 43, "v");
 
diff --git a/MilliOhmMeter_FW/src/tone_hall.cpp b/MilliOhmMeter_FW/src/tone_hall.cpp
new file mode 100644
index 0000000..9e7740c
--- /dev/null
+++ b/MilliOhmMeter_FW/src/tone_hall.cpp
@@ -0,0 +1,21 @@
+#include "tone_hall.hpp"
+
+#include <melody_player.h>
+#include <melody_factory.h>
+
+
+MelodyPlayer player(BUZZER1, LOW);
+
+void initTone(void)
+{
+  String notes[] = { "C4", "G3", "G3", "A3", "G3", "SILENCE", "B3", "C4" };
+  Melody melody = MelodyFactory.load("Nice Melody", 175, notes, 8);
+  player.play(melody);
+
+  player.playAsync(melody);
+}
+
+void handleTone(void)
+{
+
+}
\ No newline at end of file
diff --git a/MilliOhmMeter_FW/src/tone_hall.hpp b/MilliOhmMeter_FW/src/tone_hall.hpp
new file mode 100644
index 0000000..37892c7
--- /dev/null
+++ b/MilliOhmMeter_FW/src/tone_hall.hpp
@@ -0,0 +1,7 @@
+#pragma once
+
+#include "Arduino.h"
+#include "board.h"
+
+void initTone(void);
+void handleTone(void);
\ No newline at end of file