diff --git a/Cart_Reader/Cart_Reader.ino b/Cart_Reader/Cart_Reader.ino
index f131d6c..dbab6f4 100644
--- a/Cart_Reader/Cart_Reader.ino
+++ b/Cart_Reader/Cart_Reader.ino
@@ -17,6 +17,7 @@
    Rotary Enc lib: https://github.com/mathertel/RotaryEncoder
    SI5351 lib: https://github.com/etherkit/Si5351Arduino
    RTC lib: https://github.com/adafruit/RTClib
+   Frequency lib: https://github.com/PaulStoffregen/FreqCount
 
    Compiled with Arduino 1.8.13
 
diff --git a/Cart_Reader/SNES.ino b/Cart_Reader/SNES.ino
index 95b1984..4fc2d65 100644
--- a/Cart_Reader/SNES.ino
+++ b/Cart_Reader/SNES.ino
@@ -36,8 +36,14 @@ static const char snsMenuItem1[] PROGMEM = "Super Nintendo";
 static const char snsMenuItem2[] PROGMEM = "NPower SF Memory";
 static const char snsMenuItem3[] PROGMEM = "Satellaview BS-X";
 static const char snsMenuItem4[] PROGMEM = "Flash repro";
+#ifdef clockgen_calibration
+static const char snsMenuItem5[] PROGMEM = "Calibrate Clock";
+static const char snsMenuItem6[] PROGMEM = "Reset";
+static const char* const menuOptionsSNS[] PROGMEM = {snsMenuItem1, snsMenuItem2, snsMenuItem3, snsMenuItem4, snsMenuItem5, snsMenuItem6};
+#else
 static const char snsMenuItem5[] PROGMEM = "Reset";
 static const char* const menuOptionsSNS[] PROGMEM = {snsMenuItem1, snsMenuItem2, snsMenuItem3, snsMenuItem4, snsMenuItem5};
+#endif
 
 // SNES menu items
 static const char SnesMenuItem1[] PROGMEM = "Read Rom";
@@ -133,8 +139,14 @@ void snsMenu() {
   // create menu with title and 6 options to choose from
   unsigned char snsCart;
   // Copy menuOptions out of progmem
+  #ifdef clockgen_calibration
+  convertPgm(menuOptionsSNS, 6);
+  snsCart = question_box(F("Select Cart Type"), menuOptions, 6, 0);
+  #else
   convertPgm(menuOptionsSNS, 5);
   snsCart = question_box(F("Select Cart Type"), menuOptions, 5, 0);
+  #endif
+  
 
   // wait for user choice to come back from the question box menu
   switch (snsCart)
@@ -169,6 +181,12 @@ void snsMenu() {
 #endif
 
     case 4:
+#ifdef clockgen_calibration
+      clkcal();
+      break;
+
+    case 5:
+#endif    
       resetArduino();
       break;
   }
diff --git a/Cart_Reader/clkcal.ino b/Cart_Reader/clkcal.ino
new file mode 100644
index 0000000..f929160
--- /dev/null
+++ b/Cart_Reader/clkcal.ino
@@ -0,0 +1,215 @@
+//******************************************
+// Clock Calibration Module
+//******************************************
+
+#ifdef clockgen_calibration
+#include <FreqCount.h>
+#include "snes_clk.h"
+#include "SdFat.h"
+
+/******************************************
+   Variables
+ *****************************************/
+int32_t cal_factor = 0;
+int32_t old_cal = 0;
+int32_t cal_offset = 100;
+
+
+/******************************************
+   Clock Calibration
+ *****************************************/
+void clkcal()   {
+  // Adafruit Clock Generator
+  // last number is the clock correction factor which is custom for each clock generator
+  cal_factor = readClockOffset();
+
+  display.clearDisplay();
+  display.setCursor(0, 0);
+  display.print("Read correction: ");
+  display.println(cal_factor);
+  display.display();
+  delay(500);
+
+  if (cal_factor > INT32_MIN) {
+    clockgen.init(SI5351_CRYSTAL_LOAD_8PF, 0, cal_factor);
+  } else {
+    clockgen.init(SI5351_CRYSTAL_LOAD_8PF, 0, 0);
+    cal_factor = 0;
+  }
+  //clockgen.set_correction(cal_factor, SI5351_PLL_INPUT_XO);
+  clockgen.set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
+  clockgen.set_pll(SI5351_PLL_FIXED, SI5351_PLLB);
+  //clockgen.pll_reset(SI5351_PLLA);
+  //clockgen.pll_reset(SI5351_PLLB);
+  clockgen.set_freq(400000000ULL, SI5351_CLK0);
+  clockgen.set_freq(100000000ULL, SI5351_CLK1);
+  clockgen.set_freq(307200000ULL, SI5351_CLK2);
+  clockgen.output_enable(SI5351_CLK1, 1);
+  clockgen.output_enable(SI5351_CLK2, 1);
+  clockgen.output_enable(SI5351_CLK0, 1);
+
+  // Frequency Counter
+  delay(500);
+  FreqCount.begin(1000);
+  while (1) 
+  {
+    if (old_cal != cal_factor) {
+      display_Clear();
+      println_Msg(F(""));
+      println_Msg(F(""));
+      println_Msg(F(""));
+      println_Msg(F(""));
+      println_Msg(F("     Adjusting"));
+      display_Update();
+      clockgen.set_correction(cal_factor, SI5351_PLL_INPUT_XO);
+      clockgen.set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
+      clockgen.set_pll(SI5351_PLL_FIXED, SI5351_PLLB);
+      clockgen.pll_reset(SI5351_PLLA);
+      clockgen.pll_reset(SI5351_PLLB);
+      clockgen.set_freq(400000000ULL, SI5351_CLK0);
+      clockgen.set_freq(100000000ULL, SI5351_CLK1);
+      clockgen.set_freq(307200000ULL, SI5351_CLK2);
+      old_cal = cal_factor;
+      delay(500);
+    }
+    else {
+      clockgen.update_status();
+      while (clockgen.dev_status.SYS_INIT == 1) {
+      }
+  
+      if (FreqCount.available()) {
+        float count = FreqCount.read();
+        display_Clear();
+        println_Msg(F("Clock Calibration"));
+        println_Msg(F(""));
+        print_Msg(F("Freq:   "));
+        print_Msg(count);
+        println_Msg(F("Hz"));
+        print_Msg(F("Correction:"));
+        print_right(cal_factor);
+        print_Msg(F("Adjustment:"));
+        print_right(cal_offset);
+#ifdef enable_Button2
+        println_Msg(F("(Hold button to save)"));
+        println_Msg(F(""));
+        println_Msg(F("Decrease     Increase"));
+#else
+  #ifdef enable_rotary
+        println_Msg(F("Rotate to adjust"));
+  #else
+        println_Msg(F("Click/dbl to adjust"));
+  #endif
+#endif
+        display_Update();
+      }
+  #ifdef enable_Button2
+      // get input button
+      int a = checkButton1();
+      int b = checkButton2();
+  
+      // if the cart readers input button is pressed shortly
+      if (a == 1) {
+        old_cal = cal_factor;
+        cal_factor -= cal_offset;
+      }
+      if (b == 1) {
+        old_cal = cal_factor;
+        cal_factor += cal_offset;
+      }
+  
+      // if the cart readers input buttons is double clicked
+      if (a == 2) {
+        cal_offset /= 10ULL;
+        if (cal_offset < 1)
+        {
+          cal_offset = 100000000ULL;
+        }
+      }
+      if (b == 2) {
+        cal_offset *= 10ULL;
+        if (cal_offset > 100000000ULL)
+        {
+          cal_offset = 1;
+        }
+      }
+  
+      // if the cart readers input button is pressed long
+      if (a == 3) {
+        savetofile();
+      }
+      if (b == 3) {
+        savetofile();
+      }
+#else
+    //Handle inputs for either rotary encoder or single button interface.
+    int a = checkButton();
+    
+    if (a == 1) { //clockwise rotation or single click
+      old_cal = cal_factor;
+      cal_factor += cal_offset;
+    }
+
+    if (a == 2) {  //counterclockwise rotation or double click
+      old_cal = cal_factor;
+      cal_factor -= cal_offset;
+    }
+
+    if (a == 3) { //button short hold
+       cal_offset *= 10ULL;
+        if (cal_offset > 100000000ULL)
+        {
+          cal_offset = 1;
+        }
+    }
+
+    if (a == 4) { //button long hold
+      savetofile();
+    }
+#endif
+    }
+  }
+}
+
+void print_right(int32_t number)
+{
+  int32_t abs_number = number;
+  if (abs_number < 0)
+    abs_number *= -1;
+  else
+    print_Msg(F(" "));
+
+  if (abs_number == 0)
+    abs_number = 1;
+  while(abs_number < 100000000ULL)
+  {
+    print_Msg(F(" "));
+    abs_number *= 10ULL;
+  }
+  println_Msg(number);
+}
+
+void savetofile() {
+  display_Clear();
+  println_Msg(F("Saving..."));
+  println_Msg(cal_factor);
+  display_Update();
+  delay(2000);
+
+  if (!myFile.open("/snes_clk.txt", O_WRITE | O_CREAT | O_TRUNC)) {
+    print_Error(F("SD Error"), true);
+  }
+  // Write calibration factor to file
+  myFile.print(cal_factor);
+
+  // Close the file:
+  myFile.close();
+  println_Msg(F("Done"));
+  display_Update();
+  delay(1000);
+  resetArduino();
+}
+
+#endif
+//******************************************
+// End of File
+//******************************************