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diff --git a/libmaple/include/libmaple/systick.h b/libmaple/include/libmaple/systick.h
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+/******************************************************************************
+ * The MIT License
+ *
+ * Copyright (c) 2010 Perry Hung.
+ *
+ * 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/include/libmaple/systick.h
+ * @brief System timer definitions
+ */
+
+#ifndef _LIBMAPLE_SYSTICK_H_
+#define _LIBMAPLE_SYSTICK_H_
+
+#ifdef __cplusplus
+extern "C"{
+#endif
+
+#include <libmaple/libmaple_types.h>
+#include <libmaple/util.h>
+
+/** SysTick register map type */
+typedef struct systick_reg_map {
+    __io uint32 CSR;            /**< Control and status register */
+    __io uint32 RVR;            /**< Reload value register */
+    __io uint32 CNT;            /**< Current value register ("count") */
+    __io uint32 CVR;            /**< Calibration value register */
+} systick_reg_map;
+
+/** SysTick register map base pointer */
+#define SYSTICK_BASE                    ((struct systick_reg_map*)0xE000E010)
+
+/*
+ * Register bit definitions.
+ */
+
+/* Control and status register */
+
+#define SYSTICK_CSR_COUNTFLAG           BIT(16)
+#define SYSTICK_CSR_CLKSOURCE           BIT(2)
+#define SYSTICK_CSR_CLKSOURCE_EXTERNAL  0
+#define SYSTICK_CSR_CLKSOURCE_CORE      BIT(2)
+#define SYSTICK_CSR_TICKINT             BIT(1)
+#define SYSTICK_CSR_TICKINT_PEND        BIT(1)
+#define SYSTICK_CSR_TICKINT_NO_PEND     0
+#define SYSTICK_CSR_ENABLE              BIT(0)
+#define SYSTICK_CSR_ENABLE_MULTISHOT    BIT(0)
+#define SYSTICK_CSR_ENABLE_DISABLED     0
+
+/* Calibration value register */
+
+#define SYSTICK_CVR_NOREF               BIT(31)
+#define SYSTICK_CVR_SKEW                BIT(30)
+#define SYSTICK_CVR_TENMS               0xFFFFFF
+
+/** System elapsed time, in milliseconds */
+extern volatile uint32 systick_uptime_millis;
+
+/**
+ * @brief Returns the system uptime, in milliseconds.
+ */
+static inline uint32 systick_uptime(void) {
+    return systick_uptime_millis;
+}
+
+
+void systick_init(uint32 reload_val);
+void systick_disable();
+void systick_enable();
+
+/**
+ * @brief Returns the current value of the SysTick counter.
+ */
+static inline uint32 systick_get_count(void) {
+    return SYSTICK_BASE->CNT;
+}
+
+/**
+ * @brief Check for underflow.
+ *
+ * This function returns 1 if the SysTick timer has counted to 0 since
+ * the last time it was called.  However, any reads of any part of the
+ * SysTick Control and Status Register SYSTICK_BASE->CSR will
+ * interfere with this functionality.  See the ARM Cortex M3 Technical
+ * Reference Manual for more details (e.g. Table 8-3 in revision r1p1).
+ */
+static inline uint32 systick_check_underflow(void) {
+    return SYSTICK_BASE->CSR & SYSTICK_CSR_COUNTFLAG;
+}
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif