Automatically exit the printer class bootloader and start the application when...

Automatically exit the printer class bootloader and start the application when the end of the HEX file is reached (thanks to Hans Schou).

Bootloaders/Printer/BootloaderPrinter.c

@@ -73,6 +73,37 @@ struct
  */
 static bool PageDirty = false;
 
+
+/** Flag to indicate if the bootloader should be running, or should exit and allow the application code to run
+ *  via a soft reset. When cleared, the bootloader will abort, the USB interface will shut down and the application
+ *  started via a forced watchdog reset.
+ */
+static bool RunBootloader = true;
+
+/** Magic lock for forced application start. If the HWBE fuse is programmed and BOOTRST is unprogrammed, the bootloader
+ *  will start if the /HWB line of the AVR is held low and the system is reset. However, if the /HWB line is still held
+ *  low when the application attempts to start via a watchdog reset, the bootloader will re-start. If set to the value
+ *  \ref MAGIC_BOOT_KEY the special init function \ref Application_Jump_Check() will force the application to start.
+ */
+uint16_t MagicBootKey ATTR_NO_INIT;
+
+
+/** Special startup routine to check if the bootloader was started via a watchdog reset, and if the magic application
+ *  start key has been loaded into \ref MagicBootKey. If the bootloader started via the watchdog and the key is valid,
+ *  this will force the user application to start via a software jump.
+ */
+void Application_Jump_Check(void)
+{
+	/* If the reset source was the bootloader and the key is correct, clear it and jump to the application */
+	if ((MCUSR & (1 << WDRF)) && (MagicBootKey == MAGIC_BOOT_KEY))
+	{
+		MagicBootKey = 0;
+
+		// cppcheck-suppress constStatement
+		((void (*)(void))0x0000)();
+	}
+}
+
 /**
  * Determines if a given input byte of data is an ASCII encoded HEX value.
  *
@@ -255,6 +286,10 @@ static void ParseIntelHEXByte(const char ReadCharacter)
 				PageDirty = false;
 			}
 
+			/* If end of the HEX file reached, the bootloader should exit at next opportunity */
+			if (HEXParser.RecordType == HEX_RECORD_TYPE_EndOfFile)
+			  RunBootloader = false;
+
 			break;
 
 		default:
@@ -273,7 +308,7 @@ int main(void)
 	LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);
 	GlobalInterruptEnable();
 
-	for (;;)
+	while (RunBootloader)
 	{
 		USB_USBTask();
 
@@ -296,6 +331,17 @@ int main(void)
 			LEDs_SetAllLEDs(LEDMASK_USB_READY);
 		}
 	}
+
+	/* Disconnect from the host - USB interface will be reset later along with the AVR */
+	USB_Detach();
+
+	/* Unlock the forced application start mode of the bootloader if it is restarted */
+	MagicBootKey = MAGIC_BOOT_KEY;
+
+	/* Enable the watchdog and force a timeout to reset the AVR */
+	wdt_enable(WDTO_250MS);
+
+	for (;;);
 }
 
 /** Configures the board hardware and chip peripherals for the demo's functionality. */

Bootloaders/Printer/BootloaderPrinter.h

@@ -63,6 +63,9 @@
 		/** LED mask for the library LED driver, to indicate that the USB interface is busy. */
 		#define LEDMASK_USB_BUSY           LEDS_LED2
 
+		/** Magic bootloader key to unlock forced application start mode. */
+		#define MAGIC_BOOT_KEY             0xDC42
+
 	/* Enums: */
 		/** Intel HEX parser state machine states. */
 		enum HEX_Parser_States_t