SAMD20: Initial debug changes to get clocking

configs/samd20-xplained/README.txt

@@ -23,6 +23,7 @@ Contents
   - NuttX EABI "buildroot" Toolchain
   - LEDs
   - Serial Consoles
+  - Atmel Studio 6.1
   - SAMD20 Xplained Pro-specific Configuration Options
   - Configurations
 
@@ -426,6 +427,27 @@ Serial Consoles
     PA24 SERCOM3 / USART TXD
     PA25 SERCOM3 / USART RXD
 
+Atmel Studio 6.1
+^^^^^^^^^^^^^^^^
+
+  Loading Code into FLASH:
+  -----------------------
+  Tools menus:  Tool -> Device Programming.
+
+  Debugging the NuttX Object File
+  -------------------------------
+  1) Rename object file from nutt to nuttx.elf.  That is an extension that
+     will be recognized by the file menu.
+
+  2) File menu: File -> Open -> Open object file for debugging
+     - Select nuttx.elf object file
+     - Select AT91SAMD20J18
+     - Select files for symbols as desired
+     - Select debugger
+
+  3) Debug menu: Debug -> Start debugging and break
+     - This will reload the nuttx.elf file into FLASH
+
 SAMD20 Xplained Pro-specific Configuration Options
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

configs/samd20-xplained/include/board.h

@@ -335,9 +335,19 @@
 #define BOARD_PBC_FREQUENCY          (BOARD_MCK_FREQUENCY)
 #define BOARD_PBD_FREQUENCY          (BOARD_MCK_FREQUENCY)
 
-/* FLASH wait states */
+/* FLASH wait states
+ *
+ * Vdd Range     Wait states    Maximum Operating Frequency
+ * ------------- -------------- ---------------------------
+ * 1.62V to 2.7V  0             14 MHz
+ *                1             28 MHz
+ *                2             42 MHz
+ *                3             48 MHz
+ * 2.7V to 3.63V  0             24 MHz
+ *                1             48 MHz
+ */
 
-#define BOARD_FLASH_WAITSTATES       0
+#define BOARD_FLASH_WAITSTATES       1
 
 /* SERCOM definitions ***************************************************************/
 /* SERCOM4 is available on connectors EXT1 and EXT3

configs/samd20-xplained/scripts/flash.ld

@@ -44,7 +44,9 @@ MEMORY
 }
 
 OUTPUT_ARCH(arm)
+EXTERN(_vectors)
 ENTRY(_stext)
+
 SECTIONS
 {
 	.text : {