Cleaned up wirish/time, some interrupt handling refactoring:

Fixed millis(), it was just wrong, before.
Added micros(), not extensively tested.
New implementation of delayMicroseconds(). Should be more consistent
now.
Added a handful of nvic routines to enable/disable interrupts.
Cleaned up systick

10 files changed, 86 insertions, 122 deletions

diff --git a/libmaple/nvic.c b/libmaple/nvic.c
index d8745a4..56b9940 100644
--- a/libmaple/nvic.c
+++ b/libmaple/nvic.c
@@ -32,16 +32,6 @@
 #include "nvic.h"
 #include "systick.h"
 
-void nvic_disable_interrupts(void) {
-    /* Turn off all interrupts  */
-    REG_SET(NVIC_ICER0, 0xFFFFFFFF);
-    REG_SET(NVIC_ICER1, 0xFFFFFFFF);
-
-    /* Turn off systick exception  */
-    REG_CLEAR_BIT(SYSTICK_CSR, 0);
-}
-
-
 void nvic_set_vector_table(uint32 addr, uint32 offset) {
    __write(SCB_VTOR, (uint32)addr | (offset & 0x1FFFFF80));
 }
@@ -49,13 +39,9 @@ void nvic_set_vector_table(uint32 addr, uint32 offset) {
 
 /**
  *  @brief turn on interrupt number n
- *  @param[in] n interrupt number
+ *  @param n interrupt number
  */
-void nvic_enable_interrupt(uint32 n) {
-    if (n >= NVIC_NR_INTERRUPTS) {
-        return;
-    }
-
+void nvic_irq_enable(uint32 n) {
     if (n < 32) {
         REG_SET_BIT(NVIC_ISER0, n);
     } else {
@@ -65,13 +51,9 @@ void nvic_enable_interrupt(uint32 n) {
 
 /**
  *  @brief turn off interrupt number n
- *  @param[in] n interrupt number
+ *  @param n interrupt number
  */
-void nvic_disable_interrupt(uint32 n) {
-    if (n >= NVIC_NR_INTERRUPTS) {
-        return;
-    }
-
+void nvic_irq_disable(uint32 n) {
     if (n < 32) {
         REG_SET_BIT(NVIC_ICER0, n);
     } else {
diff --git a/libmaple/nvic.h b/libmaple/nvic.h
index 6cad48d..d256610 100644
--- a/libmaple/nvic.h
+++ b/libmaple/nvic.h
@@ -52,8 +52,6 @@
 #define NVIC_VectTab_RAM             ((u32)0x20000000)
 #define NVIC_VectTab_FLASH           ((u32)0x08000000)
 
-#define NVIC_NR_INTERRUPTS        60
-
 /* Where to put code  */
 #define USER_ADDR_ROM 0x08005000
 #define USER_ADDR_RAM 0x20000C00
@@ -63,15 +61,22 @@ extern "C"{
 #endif
 
 enum {
-   NVIC_USART1 = 37,
-   NVIC_USART2 = 38,
-   NVIC_USART3 = 39,
+   NVIC_TIMER1  = 27,
+   NVIC_TIMER2  = 28,
+   NVIC_TIMER3  = 29,
+   NVIC_TIMER4  = 30,
+   NVIC_USART1  = 37,
+   NVIC_USART2  = 38,
+   NVIC_USART3  = 39,
 };
 
+
+#define nvic_globalirq_enable()   asm volatile("cpsid i")
+#define nvic_globalirq_disable()  asm volatile("cpsie i")
+
 void nvic_init(void);
-void nvic_disable_interrupts(void);
-void nvic_enable_interrupt(uint32 device);
-void nvic_disable_interrupt(uint32 device);
+void nvic_irq_enable(uint32 device);
+void nvic_irq_disable(uint32 device);
 
 #ifdef __cplusplus
 }
diff --git a/libmaple/systick.c b/libmaple/systick.c
index a333528..8b0d92a 100644
--- a/libmaple/systick.c
+++ b/libmaple/systick.c
@@ -31,23 +31,25 @@
 #include "libmaple.h"
 #include "systick.h"
 
-#define MILLIS_INC 1
+#define SYSTICK_RELOAD          0xE000E014  // Reload value register
+#define SYSTICK_CNT             0xE000E018  // Current value register
+#define SYSTICK_CALIB           0xE000E01C  // Calibration value register
+
+#define SYSTICK_SRC_HCLK        BIT(2)    // Use core clock
+#define SYSTICK_TICKINT         BIT(1)    // Interrupt on systick countdown
+#define SYSTICK_ENABLE          BIT(0)    // Turn on the counter
 
 volatile uint32 systick_timer_millis = 0;
 
-void systick_init(void) {
+void systick_init(uint32 reload_val) {
     /* Set the reload counter to tick every 1ms  */
-    REG_SET_MASK(SYSTICK_RELOAD, MAPLE_RELOAD_VAL);
-//    SYSTICK_RELOAD = MAPLE_RELOAD_VAL;
+    __write(SYSTICK_RELOAD, reload_val);
 
     /* Clock the system timer with the core clock
      * and turn it on, interrrupt every 1ms to keep track of millis()*/
-    REG_SET(SYSTICK_CSR, SYSTICK_SRC_HCLK |
+    __write(SYSTICK_CSR, SYSTICK_SRC_HCLK |
                          SYSTICK_ENABLE   |
                          SYSTICK_TICKINT);
-//    SYSTICK_CSR = SYSTICK_SRC_HCLK |
-//                  SYSTICK_ENABLE   |
-//                  SYSTICK_TICKINT;
 }
 
 void SysTickHandler(void) {
diff --git a/libmaple/systick.h b/libmaple/systick.h
index d0a623f..57b724a 100644
--- a/libmaple/systick.h
+++ b/libmaple/systick.h
@@ -33,30 +33,23 @@
 
 #include "libmaple.h"
 
-/* To the ARM technical manual... there's nearly nothing on the systick
- * timer in the stm32 manual */
+#define SYSTICK_CSR             0xE000E010  // Control and status register
+#define SYSTICK_CNT             0xE000E018  // Current value register
 
-#define SYSTICK_CSR       0xE000E010  // Control and status register
-#define SYSTICK_RELOAD    0xE000E014  // Reload value register
-#define SYSTICK_CNT       0xE000E018  // Current value register
-#define SYSTICK_CALIB     0xE000E01C  // Calibration value register
-
-#define SYSTICK_SRC_HCLK  BIT(2)    // Use core clock
-#define SYSTICK_TICKINT   BIT(1)    // Interrupt on systick countdown
-#define SYSTICK_ENABLE    BIT(0)    // Turn on the counter
-
-/* We use the systick timer to tick once
- * every millisecond */
-#define MAPLE_RELOAD_VAL     72000
+#define SYSTICK_CSR_COUNTFLAG   BIT(16)
 
 #ifdef __cplusplus
 extern "C"{
 #endif
 
-void systick_init(void);
+void systick_init(uint32 reload_val);
 
 static inline uint32 systick_get_count(void) {
-    return (uint32)*(volatile uint32*)SYSTICK_CNT;
+    return __read(SYSTICK_CNT);
+}
+
+static inline uint32 systick_check_underflow(void) {
+   return (__read(SYSTICK_CSR) & SYSTICK_CSR_COUNTFLAG);
 }
 
 #ifdef __cplusplus
diff --git a/libmaple/timers.c b/libmaple/timers.c
index a3890d4..6e6653c 100644
--- a/libmaple/timers.c
+++ b/libmaple/timers.c
@@ -30,6 +30,7 @@
 
 #include "libmaple.h"
 #include "rcc.h"
+#include "nvic.h"
 #include "timers.h"
 
 typedef struct {
@@ -476,25 +477,25 @@ void timer_attach_interrupt(uint8 timer_num, uint8 compare_num, voidFuncPtr hand
     case 1:
         timer = (Timer*)TIMER1_BASE;
         timer1_handlers[compare_num-1] = handler;
-        nvic_enable_interrupt(27);
+        nvic_irq_enable(NVIC_TIMER1);
         timer->DIER |= (1 << compare_num); // 1-indexed compare nums
         break;
     case 2:
         timer = (Timer*)TIMER2_BASE;
         timer2_handlers[compare_num-1] = handler;
-        nvic_enable_interrupt(28);
+        nvic_irq_enable(NVIC_TIMER2);
         timer->DIER |= (1 << compare_num); // 1-indexed compare nums
         break;
     case 3:
         timer = (Timer*)TIMER3_BASE;
         timer3_handlers[compare_num-1] = handler;
-        nvic_enable_interrupt(29);
+        nvic_irq_enable(NVIC_TIMER3);
         timer->DIER |= (1 << compare_num); // 1-indexed compare nums
         break;
     case 4:
         timer = (Timer*)TIMER4_BASE;
         timer4_handlers[compare_num-1] = handler;
-        nvic_enable_interrupt(30);
+        nvic_irq_enable(NVIC_TIMER4);
         timer->DIER |= (1 << compare_num); // 1-indexed compare nums
         break;
     }
diff --git a/libmaple/usart.c b/libmaple/usart.c
index 53a6150..296a1fb 100644
--- a/libmaple/usart.c
+++ b/libmaple/usart.c
@@ -93,7 +93,7 @@ void usart_init(uint8 usart_num, uint32 baud) {
 
     port = usart_dev_table[usart_num].base;
     rcc_clk_enable(usart_dev_table[usart_num].rcc_dev_num);
-    nvic_enable_interrupt(usart_dev_table[usart_num].nvic_dev_num);
+    nvic_irq_enable(usart_dev_table[usart_num].nvic_dev_num);
 
     /* usart1 is mad fast  */
     clk_speed = (usart_num == USART1) ? 72000000UL : 36000000UL;
diff --git a/libmaple/util.h b/libmaple/util.h
index 8cfc60c..c336e21 100644
--- a/libmaple/util.h
+++ b/libmaple/util.h
@@ -48,8 +48,6 @@
 #define BITBAND_PERI_BASE  0x42000000
 #define BITBAND_PERI(a,b) ((BITBAND_PERI_BASE + (a-BITBAND_PERI_REF)*32 + (b*4)))  // Convert PERI address
 
-#define COUNTFLAG *((volatile unsigned char*) (BITBAND_PERI(SYSTICK_CSR,2)))
-
 #define REG_SET(reg, val)               (*(volatile uint32*)(reg)  = (val))
 #define REG_SET_BIT(reg, bit)           (*(volatile uint32*)(reg) |= BIT(bit))
 #define REG_CLEAR_BIT(reg, bit)         (*(volatile uint32*)(reg) &= ~BIT(bit))
diff --git a/wirish/time.c b/wirish/time.c
index 69e962c..c0fd03e 100644
--- a/wirish/time.c
+++ b/wirish/time.c
@@ -23,8 +23,6 @@
  * ****************************************************************************/
 
 /**
- *  @file time.c
- *
  *  @brief 
  */
 
@@ -32,46 +30,23 @@
 #include "systick.h"
 #include "time.h"
 
-#define CYCLES_PER_MICROSECOND  72
-#define FUDGE                   42
-
-extern volatile uint32 systick_timer_millis;
-
-uint32 millis() {
-   unsigned long m;
-   m = systick_timer_millis;
-   return m;
-}
-
 void delay(unsigned long ms)
 {
-   unsigned long start = millis();
-
-   while (millis() - start <= ms)
-      ;
+   uint32 i;
+   for (i = 0; i < ms; i++) {
+      delayMicroseconds(1000);
+   }
 }
 
-
-
-#if 1
 void delayMicroseconds(uint32 us) {
-    uint32 target;
-    uint32 last, cur, count;
-    /* fudge factor hacky hack hack for function overhead  */
-    target = us * CYCLES_PER_MICROSECOND - FUDGE;
-
-    /* Get current count */
-    last = systick_get_count();
-    cur = systick_get_count();
-    count = last;
-    while ((count-cur) <= target) {
-        cur = systick_get_count();
-
-        /* check for overflow  */
-        if (cur > last) {
-            count += MAPLE_RELOAD_VAL;
-        }
-        last = cur;
-    }
+    us *= 12;
+
+    /* fudge for function call overhead  */
+    us--;
+    asm volatile("   mov r0, %[us]          \n\t"
+                 "1: subs r0, #1            \n\t"
+                 "   bhi 1b                 \n\t"
+                 :
+                 : [us] "r" (us)
+                 : "r0");
 }
-#endif
diff --git a/wirish/time.h b/wirish/time.h
index 9e5536b..45e82dc 100644
--- a/wirish/time.h
+++ b/wirish/time.h
@@ -23,8 +23,6 @@
  * ****************************************************************************/
 
 /**
- *  @file time.h
- *
  *  @brief 
  */
 
@@ -34,32 +32,42 @@
 #ifdef __cplusplus
 extern "C"{
 #endif
-/* Returns time since boot in milliseconds  */
-uint32 millis(void);
+
+#include "nvic.h"
+#include "systick.h"
+
+#define CYCLES_PER_MICROSECOND  72
+#define US_PER_MS               1000
+#define MAPLE_RELOAD_VAL        72000
+
+extern volatile uint32 systick_timer_millis;
+
+/* time in milliseconds since boot  */
+static inline uint32 millis(void) {
+   return systick_timer_millis;
+}
 
 /* Time in microseconds since boot  */
-uint32 micros(void);
+static inline uint32 micros(void) {
+   uint32 ms;
+   uint32 cycle_cnt;
+   uint32 res;
 
-/* Delay for ms milliseconds  */
-void delay(unsigned long ms);
+   nvic_globalirq_disable();
 
-/* Delay for us microseconds  */
-void delayMicroseconds(uint32 us);
+   cycle_cnt = systick_get_count();
+   ms = millis();
+
+   nvic_globalirq_enable();
 
-#if 0
-static inline void delay_us(uint32 us) {
-    us *= 12;
-    asm volatile("mov  r0, %[us]        \n\t"
-                 "subs r0, #2 \n\t"
-"1:                                    \n\t"
-                  "subs r0, r0, #1           \n\t"
-                  "bne 1b"
-                 :
-                 : [us] "r" (us)
-                 : "r0", "cc");
+   res = (ms * US_PER_MS) + (MAPLE_RELOAD_VAL - cycle_cnt)/CYCLES_PER_MICROSECOND;
 
+   return res;
 }
-#endif
+
+void delay(unsigned long ms);
+void delayMicroseconds(uint32 us);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif
diff --git a/wirish/wirish.c b/wirish/wirish.c
index 1938ec9..4281875 100644
--- a/wirish/wirish.c
+++ b/wirish/wirish.c
@@ -53,7 +53,7 @@ void init(void) {
    rcc_set_prescaler(RCC_PRESCALER_APB2, RCC_APB2_HCLK_DIV_1);
 
    nvic_init();
-   systick_init();
+   systick_init(MAPLE_RELOAD_VAL);
    gpio_init();
    adc_init();
    timer_init(1, 1);