basic led gpio driver

[cortex-from-scratch] / ivt.c

diff --git a/ivt.c b/ivt.c
index a6761d0..9f8e643 100644 (file)
--- a/ivt.c
+++ b/ivt.c
@@ -56,50 +56,42 @@ struct interrupt_frame {
 
 /* 
  * Vector table, each entry contains an interrupt
- * service routine:  
- *
+ * service routine: 
  * interrupt vector 1-15: processor exceptions
  * interrupt vector 16-92: irq0 - irq ..
- *
  * Vector table needs to be aligned in memory.
  * */
-
 uint32_t __attribute__((aligned(0x100))) ivt[92];
 
-/* each message corresponds to each and every exception. 
- * We get the correct message by accessing
- *  exception_message[interrupt_number] 
- *  exception_message[0] is not used (=MSP)*/
-
+/* Each message corresponds to each and every exception. */
 char * exception_message(uint8_t intnr) {
 
-       char * messages[] = {
-           "--",
-           "RESET",
-           "NMI",
-           "HARD FAULT",
-           "MEMMANAGE FAULT",
-           "BUS FAULT",
-           "USAGE FAULT",
-           "RESERVED",
-           "SVC",
-           "DEBUG MONITOR",
-           "RESERVED",
-           "RESERVED",
-           "RESERVED",
-           "RESERVED",
-           "PENDSV",
-           "SYSTICK",
-           "IRQ1",
-           "IRQ2",
-           "IRQ3",
-           "IRQ4",
-           // add more if needed
-       };
-
-       if (intnr < 20) // TODO: strlen
-               return messages[intnr];
+char * messages[] = {
+    "--",
+    "RESET",
+    "NMI",
+    "HARD FAULT",
+    "MEMMANAGE FAULT",
+    "BUS FAULT",
+    "USAGE FAULT",
+    "RESERVED",
+    "SVC",
+    "DEBUG MONITOR",
+    "RESERVED",
+    "RESERVED",
+    "RESERVED",
+    "RESERVED",
+    "PENDSV",
+    "SYSTICK",
+    "IRQ1",
+    "IRQ2",
+    "IRQ3",
+    "IRQ4",
+    // add more if needed
+};
 
+if (intnr < 20) // TODO: strlen
+       return messages[intnr];
        return NULL;
 }
 
@@ -107,11 +99,11 @@ void ivt_set_gate(unsigned char num, void * isr(), short pri) {
 
        ivt[num] = (uint32_t) isr;
        *NVIC_ISER0 = (1 << ((uint32_t)(num) & 0x1F));
-       /* Priorities */
+       /* TODO: Priorities */
 }
 
 
-/* Dummy interrupt: comment out the comment to use a naked f
+/* Dummy interrupt: comment out the comment to use a naked
  * function */
 
 // __attribute__ ((interrupt)) 
@@ -129,13 +121,16 @@ void * dummy_isr(/* struct interrupt_frame * frame */) {
 /* Initialize interrupt vector  */
 void ivt_init() {
 
-       /* clear entire IVT, in SRAM location for SRAM + .data (in .bss section) */
+       /* clear entire IVT location in memory  */
        memset(&ivt, 0, (sizeof(uint32_t) * 92));
 
-       // stack top is loaded from the first entry table on boot/reset
-       // don't need to relocate or init this here
+       /* The reset, NMI and hardfault handlers are originally
+        * defined in the assembly start up and can be 
+        * reused or overwritten. 
+       *  */
        extern void * reset,  * nmi, * hardfault;
 
+       // set dummy handlers 
        for (int i = 1; i <= 64 ; i++) {
                ivt_set_gate(i, dummy_isr, 0);
        }