From 45fec7ac2438081bc52889a4af7d95d0aafbd7ee Mon Sep 17 00:00:00 2001
From: Sadeep Madurange <sadeep@asciimx.com>
Date: Wed, 11 Sep 2024 16:23:30 +0800
Subject: LED works!

---
 README.txt |  2 +-
 main.c     | 17 ++++++++++++++---
 script.ld  | 23 +++++++++++++++--------
 3 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/README.txt b/README.txt
index ab93862..faa5291 100644
--- a/README.txt
+++ b/README.txt
@@ -1,5 +1,5 @@
 Compile and upload
 
-$ arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -o a.elf main.c
+$ arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -T script.ld -nostartfiles -nostdlib -o a.elf main.c
 $ arm-none-eabi-objcopy -O ihex -j .text -j .data a.elf a.hex
 $ avrdude -c arduino -p atmel_sam3x8e -v -b 115200 -U flash:w:a.hex
diff --git a/main.c b/main.c
index 8fcc9be..89c1e15 100644
--- a/main.c
+++ b/main.c
@@ -25,9 +25,9 @@
 int main(void)
 {
 	// enable peripheral clock
-	PMC_WPMR = PMC_WPKEY << 8;
-	PMC_PCER0 |= (1u << PMC_PID);
-	PMC_WPMR = (PMC_WPKEY << 8) | 1u;
+	//PMC_WPMR = PMC_WPKEY << 8;
+	//PMC_PCER0 |= (1u << PMC_PID);
+	//PMC_WPMR = (PMC_WPKEY << 8) | 1u;
 
 	// enable port, set to output, disable pull-up
 	PIO_WPMR = PIO_WPKEY << 8;
@@ -44,3 +44,14 @@ int main(void)
 
 	return 0;
 }
+
+extern const unsigned int StackTop;
+
+__attribute__ ((section(".vtor")))
+const void* VectorTable[] = {
+    &StackTop,   /* CPU will automatically       *
+                  * set stack its pointer        *
+                  * to this value                */
+
+    main,        /* -15: Reset_IRQn              */
+};
diff --git a/script.ld b/script.ld
index e8b0bb1..ac49459 100644
--- a/script.ld
+++ b/script.ld
@@ -1,3 +1,5 @@
+ENTRY(main)
+
 MEMORY
 {
 	rom (rx)  : ORIGIN = 0x00080000, LENGTH = 0x00080000
@@ -6,21 +8,28 @@ MEMORY
 
 SECTIONS
 {
-	. = ALIGN(4);
 	.text :
 	{
-		KEEP(*(.vectors .vectors.*))
+		KEEP(*(.vtor))
+
 		*(.text*)
 		*(.rodata*)
+
+		. = ALIGN(4);
+		__end_of_text__ = .;
 	} > rom
 
-	. = ALIGN(4);
 	.data :
 	{
-		*(.data*);
+		__data_start_src__ = __end_of_text__;
+		__data_start__ = .;
+
+		*(.data*)
+
+		. = ALIGN(4);
+		__data_end__ = .;
 	} > ram AT >rom
 
-	. = ALIGN(4);
 	.bss (NOLOAD) :
 	{
 		__bss_start__ = . ;
@@ -29,7 +38,5 @@ SECTIONS
 		__bss_end__ = . ;
 	} > ram
 
-	_end = . ;
-	__end__ = _end ;
-	end = _end;
+	StackTop = ORIGIN(ram) + LENGTH(ram);
 }
-- 
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