Moved bootloader entry earlier from Reset handler

Make sure system clocks or anything else is not yet initialized before calling ROM bootloader

Author: ppescher

Diff for: cores/arduino/Reset.cpp

@@ -25,7 +25,7 @@ extern "C" {
 
 #define RESET_TO_BOOTLOADER_MAGIC_CODE 0xDEADBEEF
 
-uint32_t reset_to_bootloader_magic __attribute__ ((section (".noinit")));
+uint32_t reset_to_bootloader_magic;
 
 void checkBoot()
 {

Diff for: cores/arduino/stm32/clock.c

@@ -84,8 +84,8 @@ void SysTick_Handler(void)
 {
   HAL_IncTick();
   HAL_SYSTICK_IRQHandler();
-  osSystickHandler();
   tickReset();
+  osSystickHandler();
 }
 
 /**

Diff for: cores/arduino/stm32/hw_config.c

@@ -50,8 +50,6 @@
   */
 void hw_config_init(void)
 {
-  checkBoot();
-
   //Initialize the HAL
   HAL_Init();
 

Diff for: cores/arduino/stm32/startup_stm32yyxx.S

@@ -2,3 +2,16 @@
 
 #include CMSIS_STARTUP_FILE
 
+/* Bootloader entry check done early at reset (then jump into original entry point) */
+
+    .section	.text.Boot_Reset_Handler
+	.type	Boot_Reset_Handler, %function
+	.thumb_set Reset_Handler,Boot_Reset_Handler
+Boot_Reset_Handler:
+  ldr   sp, =_estack    /* Atollic update: set stack pointer */
+  bl    checkBoot
+/* Copy the data segment initializers from flash to SRAM */
+  movs	r1, #0
+  b	LoopCopyDataInit    /* Jump to original Reset_Handler */
+    
+.size	Boot_Reset_Handler, .-Boot_Reset_Handler