1 files changed, 88 insertions, 0 deletions
diff --git a/libmaple/systick.c b/libmaple/systick.c
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+/******************************************************************************
+ * The MIT License
+ *
+ * Copyright (c) 2010 Perry Hung.
+ * Copyright (c) 2010, 2011 LeafLabs, LLC.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *****************************************************************************/
+
+/**
+ * @file libmaple/systick.c
+ * @brief System timer (SysTick).
+ */
+
+#include <libmaple/systick.h>
+
+volatile uint32 systick_uptime_millis;
+static void (*systick_user_callback)(void);
+
+/**
+ * @brief Initialize and enable SysTick.
+ *
+ * Clocks the system timer with the core clock, turns it on, and
+ * enables interrupts.
+ *
+ * @param reload_val Appropriate reload counter to tick every 1 ms.
+ */
+void systick_init(uint32 reload_val) {
+    SYSTICK_BASE->RVR = reload_val;
+    systick_enable();
+}
+
+/**
+ * Clock the system timer with the core clock, but don't turn it
+ * on or enable interrupt.
+ */
+void systick_disable() {
+    SYSTICK_BASE->CSR = SYSTICK_CSR_CLKSOURCE_CORE;
+}
+
+/**
+ * Clock the system timer with the core clock and turn it on;
+ * interrupt every 1 ms, for systick_timer_millis.
+ */
+void systick_enable() {
+    /* re-enables init registers without changing reload val */
+    SYSTICK_BASE->CSR = (SYSTICK_CSR_CLKSOURCE_CORE   |
+                         SYSTICK_CSR_ENABLE           |
+                         SYSTICK_CSR_TICKINT_PEND);
+}
+
+/**
+ * @brief Attach a callback to be called from the SysTick exception handler.
+ *
+ * To detach a callback, call this function again with a null argument.
+ */
+void systick_attach_callback(void (*callback)(void)) {
+    systick_user_callback = callback;
+}
+
+/*
+ * SysTick ISR
+ */
+
+void __exc_systick(void) {
+    systick_uptime_millis++;
+    if (systick_user_callback) {
+        systick_user_callback();
+    }
+}