Independent watchdog refactor.

2 files changed, 88 insertions, 38 deletions

diff --git a/libmaple/iwdg.c b/libmaple/iwdg.c
index 82a0151..3d67ee8 100644
--- a/libmaple/iwdg.c
+++ b/libmaple/iwdg.c
@@ -23,34 +23,37 @@
  *****************************************************************************/
 
 /**
- *  @file iwdg.c
- *
- *  @brief Independent watchdog support
+ * @file iwdg.c
+ * @brief Independent watchdog (IWDG) support
  */
 
-#include "libmaple.h"
 #include "iwdg.h"
 
-#define IWDG_UNLOCK   0x5555
-#define IWDG_START    0xCCCC
-#define IWDG_FEED     0xAAAA
-
 /**
- *  @brief Initialise and start the watchdog
+ * @brief Initialise and start the watchdog
+ *
+ * The prescaler and reload set the timeout.  A prescaler of 3 divides
+ * the 40 kHz clock by 32 and gives roughly 1 ms per reload.
  *
- *  The prescaler and reload set the timeout.  A prescaler of 3 divides
- *  the 40 kHz clock by 32 and gives roughly 1 ms per reload.
+ * @param prescaler Prescaler for the 40 KHz IWDG clock.
+ * @param reload Independent watchdog counter reload value.
  */
-void iwdg_init(uint8 prescaler, uint16 reload) {
-    __write(IWDG_KR, IWDG_UNLOCK);
-    __write(IWDG_PR, prescaler);
-    __write(IWDG_RLR, reload);
+void iwdg_init(iwdg_prescaler prescaler, uint16 reload) {
+   IWDG_BASE->KR = IWDG_KR_UNLOCK;
+   IWDG_BASE->PR = prescaler;
+   IWDG_BASE->RLR = reload;
 
-    /* Start things off */
-    __write(IWDG_KR, IWDG_START);
-    __write(IWDG_KR, IWDG_FEED);
+   /* Start things off */
+   IWDG_BASE->KR = IWDG_KR_START;
+   iwdg_feed();
 }
 
+/**
+ * @brief Reset the IWDG counter.
+ *
+ * Calling this function will cause the IWDG counter to be reset to
+ * its reload value.
+ */
 void iwdg_feed(void) {
-    __write(IWDG_KR, IWDG_FEED);
+    IWDG_BASE->KR = IWDG_KR_FEED;
 }
diff --git a/libmaple/iwdg.h b/libmaple/iwdg.h
index 4ab0ddf..81f0fdb 100644
--- a/libmaple/iwdg.h
+++ b/libmaple/iwdg.h
@@ -23,35 +23,82 @@
  *****************************************************************************/
 
 /**
- *  @file iwdg.h
+ * @file iwdg.h
+ * @author Michael Hope, Marti Bolivar <mbolivar@leaflabs.com>
+ * @brief Independent watchdog support.
  *
- *  @brief Independent watchdog support
+ * To use the independent watchdog, first call iwdg_init() with the
+ * appropriate prescaler and IWDG counter reload values for your
+ * application.  Afterwards, you must periodically call iwdg_feed()
+ * before the IWDG counter reaches 0 to reset the counter to its
+ * reload value.  If you do not, the chip will reset.
+ *
+ * Once started, the independent watchdog cannot be turned off.
  */
 
 #ifndef _IWDG_H_
 #define _IWDG_H_
 
+#include "libmaple_types.h"
+
 #ifdef __cplusplus
 extern "C"{
 #endif
 
-#define IWDG_BASE               0x40003000
-#define IWDG_KR                 (IWDG_BASE + 0x0)
-#define IWDG_PR                 (IWDG_BASE + 0x4)
-#define IWDG_RLR                (IWDG_BASE + 0x8)
-#define IWDG_SR                 (IWDG_BASE + 0xC)
-
-enum {
-    IWDG_PRE_4,
-    IWDG_PRE_8,
-    IWDG_PRE_16,
-    IWDG_PRE_32,
-    IWDG_PRE_64,
-    IWDG_PRE_128,
-    IWDG_PRE_256
-};
-
-void iwdg_init(uint8 prescaler, uint16 reload);
+/*
+ * Register map
+ */
+
+/** Independent watchdog register map type. */
+typedef struct iwdg_reg_map {
+    __io uint32 KR;             /**< Key register. */
+    __io uint32 PR;             /**< Prescaler register. */
+    __io uint32 RLR;            /**< Reload register. */
+    __io uint32 SR;             /**< Status register */
+} iwdg_reg_map;
+
+#define IWDG_BASE                       ((struct iwdg_reg_map*)0x40003000)
+
+/*
+ * Register bit definitions
+ */
+
+/* Key register */
+
+#define IWDG_KR_UNLOCK                  0x5555
+#define IWDG_KR_FEED                    0xAAAA
+#define IWDG_KR_START                   0xCCCC
+
+/* Prescaler register */
+
+#define IWDG_PR_DIV_4                   0x0
+#define IWDG_PR_DIV_8                   0x1
+#define IWDG_PR_DIV_16                  0x2
+#define IWDG_PR_DIV_32                  0x3
+#define IWDG_PR_DIV_64                  0x4
+#define IWDG_PR_DIV_128                 0x5
+#define IWDG_PR_DIV_256                 0x6
+
+/* Status register */
+
+#define IWDG_SR_RVU_BIT                 1
+#define IWDG_SR_PVU_BIT                 0
+
+#define IWDG_SR_RVU                     BIT(IWDG_SR_RVU_BIT)
+#define IWDG_SR_PVU                     BIT(IWDG_SR_PVU_BIT)
+
+/** Independent watchdog prescalers */
+typedef enum {
+    IWDG_PRE_4 = IWDG_PR_DIV_4,
+    IWDG_PRE_8 = IWDG_PR_DIV_8,
+    IWDG_PRE_16 = IWDG_PR_DIV_16,
+    IWDG_PRE_32 = IWDG_PR_DIV_32,
+    IWDG_PRE_64 = IWDG_PR_DIV_64,
+    IWDG_PRE_128 = IWDG_PR_DIV_128,
+    IWDG_PRE_256 = IWDG_PR_DIV_256
+} iwdg_prescaler;
+
+void iwdg_init(iwdg_prescaler prescaler, uint16 reload);
 void iwdg_feed(void);
 
 #ifdef __cplusplus