the led is finally working

.vscode/settings.json

@@ -16,6 +16,7 @@
         "stdexcept": "cpp",
         "streambuf": "cpp",
         "system_error": "cpp",
-        "tuple": "cpp"
+        "tuple": "cpp",
+        "main.h": "c"
     }
 }

numworks_port/src/linker.ld

@@ -2,7 +2,6 @@
 /*ENTRY(reset_handler)*/
 /* End of RAM / Start of stack */
 /* (4KB SRAM) */
-_estack = 0x20262144;
 
 /* epsilon stuff */
 STACK_SIZE = 32K;
@@ -85,6 +84,13 @@ SECTIONS
     *(.rodata.*)
   } >FLASH
 
+  .init_array : {
+    . = ALIGN(4);
+    _init_array_start = .;
+    KEEP (*(.init_array*))
+    _init_array_end = .;
+  } >FLASH
+
   /* The 'data' section is space set aside in RAM for
    * things like variables, which can change. */
   .data : {

numworks_port/src/rt0.cpp

@@ -1,5 +1,9 @@
 #include "vector_table.h"
 #include <stddef.h>
+#include <stdint.h>
+#include "device/stm32f730xx.h"
+
+#define LED_PIN    (4) // PC0
 
 typedef void (*cxx_constructor)();
 
@@ -52,8 +56,19 @@ void __attribute__((noinline)) start() {
   size_t bssSectionLength = (&_bss_section_end_ram - &_bss_section_start_ram);
   memset_custom(&_bss_section_start_ram, 0, bssSectionLength);
 
+  // Enable the GPIOa and GPIOC peripheral in RCC.
+  RCC->AHB1ENR   |= RCC_AHB1ENR_GPIOBEN ;
+
+  // C0 is connected to the LED.
+  // It should be set to push-pull low-speed output.
+  GPIOB->MODER  &= ~(0x3 << (LED_PIN*2));
+  GPIOB->MODER  |=  (0x1 << (LED_PIN*2));
+  GPIOB->OTYPER &= ~(1 << LED_PIN);
+
+  GPIOB->ODR = (1 << LED_PIN);
+
   while (0)
   {
-    /* code */
+    GPIOB->ODR = (1 << LED_PIN);
   }
 }

numworks_port/src/vector_table.cpp

@@ -1,5 +1,5 @@
 #include "vector_table.h"
-extern const void * _estack;
+extern const void * _stack_start;
 
 /* Interrupt Service Routines are void->void functions */
 typedef void(*ISR)(void);
@@ -16,7 +16,7 @@ ISR InitialisationVector[INITIALISATION_VECTOR_SIZE]
   __attribute__((section(".isr_vector_table")))
   __attribute__((used))
   = {
-  (ISR)&_estack, // Stack start
+  (ISR)&_stack_start, // Stack start
   start, // Reset service routine,
   0, // NMI service routine,
   0, // HardFault service routine,