add #26 double reset to DFU, only work with nrf52840 (won't work with nrf52832)

src/linker/s132_v6.ld

@@ -14,7 +14,10 @@ MEMORY
   FLASH (rx) : ORIGIN = 0x74000, LENGTH = 0xA000 /* 40 KB */
 
   /** RAM Region for bootloader. */
-  RAM (rwx) :  ORIGIN = 0x20003000, LENGTH = 0x20007F80-0x20003000
+  RAM (rwx) :  ORIGIN = 0x20003000, LENGTH = 0x20007F7C-0x20003000
+
+  /* Location for double reset detection, no init */
+  DBL_RESET (rwx) :  ORIGIN = 0x20007F7C, LENGTH = 0x04
 
   /** Location of non initialized RAM. Non initialized RAM is used for exchanging bond information
    *  from application to bootloader when using buttonluss DFU OTA. 
@@ -66,6 +69,11 @@ SECTIONS
   {
     KEEP(*(.uicrMbrParamsPageAddress))
   } > UICR_MBR_PARAM_PAGE
+  
+  .dbl_reset(NOLOAD) :
+  {
+
+  } > DBL_RESET  
 
   /* No init RAM section in bootloader. Used for bond information exchange. */
   .noinit(NOLOAD) :

src/linker/s140_v6.ld

@@ -17,10 +17,14 @@ MEMORY
   /* Avoid conflict with NOINIT for OTA bond sharing */
   RAM (rwx) :  ORIGIN = 0x20008000, LENGTH = 0x20040000-0x20008000
 
+  /* Location for double reset detection, no init */
+  DBL_RESET (rwx) :  ORIGIN = 0x20007F7C, LENGTH = 0x04
+  
   /** Location of non initialized RAM. Non initialized RAM is used for exchanging bond information
    *  from application to bootloader when using buttonluss DFU OTA. 
    */
   NOINIT (rwx) :  ORIGIN = 0x20007F80, LENGTH = 0x80
+  
 
   /** Location of bootloader setting in flash. */
   BOOTLOADER_SETTINGS (rw) : ORIGIN = 0x000FF000, LENGTH = 0x1000
@@ -68,11 +72,17 @@ SECTIONS
     KEEP(*(.uicrMbrParamsPageAddress))
   } > UICR_MBR_PARAM_PAGE
 
+  .dbl_reset(NOLOAD) :
+  {
+
+  } > DBL_RESET
+
   /* No init RAM section in bootloader. Used for bond information exchange. */
   .noinit(NOLOAD) :
   {
 
   } > NOINIT
+
   /* other placements follow here... */
 }