diff --git a/keywords.txt b/keywords.txt
index 63d9865..afbded0 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -47,6 +47,7 @@ drawSlowXYBitmap	KEYWORD2
 drawTriangle	KEYWORD2
 enabled	KEYWORD2
 everyXFrames	KEYWORD2
+exitToBootloader	KEYWORD2
 fillCircle	KEYWORD2
 fillRect	KEYWORD2
 fillRoundRect	KEYWORD2
@@ -68,6 +69,7 @@ initRandomSeed	KEYWORD2
 invert	KEYWORD2
 justPressed	KEYWORD2
 justReleased	KEYWORD2
+mainNoUSB	KEYWORD2
 nextFrame	KEYWORD2
 nextFrameDEV	KEYWORD2
 notPressed	KEYWORD2
diff --git a/src/Arduboy2Core.cpp b/src/Arduboy2Core.cpp
index cb6167a..93d3cc1 100644
--- a/src/Arduboy2Core.cpp
+++ b/src/Arduboy2Core.cpp
@@ -476,3 +476,73 @@ void Arduboy2Core::delayShort(uint16_t ms)
   delay((unsigned long) ms);
 }
 
+// reset to the bootloader using the watchdog timer
+void Arduboy2Core::exitToBootloader()
+{
+  // prevent the bootloader magic number from being overwritten by timer 0
+  // when a timer variable overlaps the magic number location.
+  power_timer0_disable();
+
+  *(uint16_t *)MAGIC_KEY_POS = MAGIC_KEY;
+  wdt_enable(WDTO_15MS);
+
+  while (true) { }
+}
+
+void Arduboy2Core::mainNoUSB()
+{
+  init();
+
+  // disable USB
+  UDCON = _BV(DETACH);
+  USBCON = _BV(FRZCLK);
+  power_usb_disable();
+
+#ifdef ARDUBOY_10
+  // Set the UP button pin for INPUT_PULLUP
+  PORTF |= _BV(UP_BUTTON_BIT);
+  DDRF &= ~(_BV(UP_BUTTON_BIT));
+
+  // Set RGB led to magenta
+  PORTB |= _BV(GREEN_LED_BIT); // green off (high)
+  PORTB &= ~(_BV(RED_LED_BIT)); // red on (low)
+  PORTB &= ~(_BV(BLUE_LED_BIT)); // blue on (low)
+  // set RGB led pins as outputs
+  DDRB |= _BV(RED_LED_BIT) | _BV(GREEN_LED_BIT) | _BV(BLUE_LED_BIT);
+
+  // Delay to give time for the UP pin to be pulled high if it was floating
+  for (volatile uint8_t i = 0; i < 100; i++) { }
+
+  // if the UP button is pressed
+  if ((PINF & _BV(UP_BUTTON_BIT)) == 0) {
+    exitToBootloader();
+  }
+#elif defined(AB_DEVKIT)
+//TODO do above for DevKit (light the blue LED)
+#endif
+
+  // The remainder is a copy of the Arduino main() function with the
+  // USB code and other unneeded code commented out.
+  // init() was called above.
+  // The call to function initVariant() is commented out to fix compiler
+  // error: "multiple definition of 'main'".
+  // The return statment is removed since this function is type void.
+
+//  init();
+
+//  initVariant();
+
+//#if defined(USBCON)
+//  USBDevice.attach();
+//#endif
+
+  setup();
+
+  for (;;) {
+    loop();
+//    if (serialEventRun) serialEventRun();
+  }
+
+//  return 0;
+}
+
diff --git a/src/Arduboy2Core.h b/src/Arduboy2Core.h
index 324ae15..ad9746d 100644
--- a/src/Arduboy2Core.h
+++ b/src/Arduboy2Core.h
@@ -10,6 +10,7 @@
 #include <Arduino.h>
 #include <avr/power.h>
 #include <avr/sleep.h>
+#include <avr/wdt.h>
 #include <limits.h>
 
 
@@ -689,6 +690,22 @@ class Arduboy2Core
      */
     void static delayShort(uint16_t ms) __attribute__ ((noinline));
 
+    /** \brief
+     * Exit the sketch and start the bootloader
+     *
+     * \details
+     * TODO add details including cautions and warnings
+     */
+    void static exitToBootloader();
+
+    /** \brief
+     * Arduino main() function without USB
+     *
+     * \details
+     * TODO add details including cautions and warnings
+     */
+    void static mainNoUSB();
+
   protected:
     // internals
     void static setCPUSpeed8MHz();