From: Peter Henn <Peter.Henn@web.de>
Date: Fri, 31 Dec 2021 04:35:47 +0000 (+0000)
Subject: Use a board specific bootloader and application start
X-Git-Tag: DFU-Bootloader-ProMicro~6
X-Git-Url: http://git.linex4red.de/pub/lufa.git/commitdiff_plain/a1b608ddabc6afd936ebb2cb6182906addeb38c2

Use a board specific bootloader and application start

- Add board specific Application_Jump_Check match for Pro-Micro
  and Micro boards
- Add in fixed FUSE_BOOTRST check in Application_Jump_Check for
  all other boards
- Enhance MagicBootKey handling
- Let Reset flags untouched for application code if reset was not
  forced by the bootloader
---

diff --git a/Bootloaders/DFU/BootloaderDFU.c b/Bootloaders/DFU/BootloaderDFU.c
index eb6c06984..ec8f0fa66 100644
--- a/Bootloaders/DFU/BootloaderDFU.c
+++ b/Bootloaders/DFU/BootloaderDFU.c
@@ -131,7 +131,53 @@ void Application_Jump_Check(void)
 
 		/* Re-enable JTAG debugging */
 		JTAG_ENABLE();
+	#elif ((BOARD == BOARD_PROMICRO) || (BOARD == BOARD_MICRO))
+		/* Pro-Micro and Arduino Micro board use power-on reset, but no external reset. Both boards have
+		 * the hardware bootloader pin HWBE enabled. Unfortunately only the external reset allows together
+		 * with an enabled HWBE that the CPU start at the bootloader address independent of the FUSE_BOOTRST.
+		 * That means the power-on reset will start just controlled by the FUSE_BOOTRST the bootloader or
+		 * direct in the application and cannot be overridden by HWBE signal. Therfore FUSE_BOOTRST shall
+		 * be enabled, otherwise the bootloader will not be reached for these boards.
+		 * The bootloader checks FUSE_HWBE as *unprogammed* instead of FUSE_BOOTRST as programmed on other
+		 * board variants to decide fast application start, without waiting the dedicted bootloader timeout
+		 * in case of a USB, watchdog, brown-out or JTAG reset. If the watchdog reset was initiated from
+		 * the bootloader marked with the MAGIC_BOOT_KEY this reset flag is reset. All other reset flags
+		 * are left untouched to allow the application code checking the reset signals, especially in case
+		 * of application fast start.
+		 * The bootloader is entered always for external reset and power-on reset. But the bootloader is
+		 * anyway exited after that dedicted timeout, if a reset-vector to the application is programmed.
+		 * Once a DFU program interacts this the bootloader during this dedicted timeout, the timer stops
+		 * and the application needs to be started by DFU bootloader command manually or using a reset.
+		 */
+
+		/* Check if the device's forced Bootloader via Hardware Bootenable is unprogrammed */
+		if (BootloaderAPI_ReadFuse(GET_EXTENDED_FUSE_BITS) & ~FUSE_HWBE)
+		{
+			/* If the reset source was not an external or power-on reset jump to the application */
+			if (!(MCUSR & ((1 << EXTRF) || (1 << PORF))))
+			  JumpToApplication = true;
+		}
+		/* If the reset source was the bootloader and the key is correct, clear it and jump to the application;
+		 * this can happen in the HWBE fuse is set, and the HBE pin is low during the watchdog reset */
+		if ((MCUSR & (1 << WDRF)) && (MagicBootKey == MAGIC_BOOT_KEY))
+		{
+			JumpToApplication = true;
+
+			/* Clear reset source */
+			MCUSR &= ~(1 << WDRF);
+		}
 	#else
+		/* Check if the device's BOOTRST fuse is set */
+		if (!(BootloaderAPI_ReadFuse(GET_HIGH_FUSE_BITS) & ~FUSE_BOOTRST))
+		{
+			/* If the reset source was not an external reset or the key is correct, clear it and jump to the application */
+			if (!(MCUSR & (1 << EXTRF)) || (MagicBootKey == MAGIC_BOOT_KEY))
+			  JumpToApplication = true;
+
+			/* Clear reset source */
+			MCUSR &= ~(1 << EXTRF);
+		}
+		else
 		{
 			/* If the reset source was the bootloader and the key is correct, clear it and jump to the application;
 			 * this can happen in the HWBE fuse is set, and the HBE pin is low during the watchdog reset */
@@ -143,6 +189,9 @@ void Application_Jump_Check(void)
 		}
 	#endif
 
+	/* Clear the boot key in any case */
+	MagicBootKey = 0;
+
 	/* Don't run the user application if the reset vector is blank (no app loaded) */
 	bool ApplicationValid = (pgm_read_word_near(0) != 0xFFFF);
 
@@ -150,12 +199,8 @@ void Application_Jump_Check(void)
 	if (JumpToApplication && ApplicationValid)
 	{
 		/* Turn off the watchdog */
-		MCUSR &= ~(1 << WDRF);
 		wdt_disable();
 
-		/* Clear the boot key and jump to the user application */
-		MagicBootKey = 0;
-
 		// cppcheck-suppress constStatement
 		((void (*)(void))0x0000)();
 	}