unified systick handling

the only change this results in in the example binaries is in the
hackrf-jellybean/systick example, where the the check in
systick_set_clocksource for overflowing from the stm32 area gets used.

lib/cm3/systick.c

@@ -0,0 +1,149 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2010 Thomas Otto <tommi@viadmin.org>
+ * Copyright (C) 2012 Benjamin Vernoux <titanmkd@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/** @defgroup CM3_systick_file SysTick
+
+@ingroup CM3_files
+
+@brief <b>libopencm3 Cortex System Tick Timer</b>
+
+@version 1.0.0
+
+@author @htmlonly &copy; @endhtmlonly 2010 Thomas Otto <tommi@viadmin.org>
+
+@date 19 August 2012
+
+This library supports the System Tick timer in ARM Cortex Microcontrollers.
+
+The System Tick timer is part of the ARM Cortex core. It is a 24 bit
+down counter that can be configured with an automatical reload value.
+
+LGPL License Terms @ref lgpl_license
+ */
+
+/**@{*/
+#include <libopencm3/cm3/systick.h>
+
+/*-----------------------------------------------------------------------------*/
+/** @brief SysTick Set the Automatic Reload Value.
+
+The counter is set to the reload value when the counter starts and after it
+reaches zero.
+
+@param[in] value u32. 24 bit reload value.
+*/
+
+void systick_set_reload(u32 value)
+{
+	STK_LOAD = (value & 0x00FFFFFF);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief SysTick Read the Automatic Reload Value.
+
+@returns 24 bit reload value as u32.
+*/
+
+u32 systick_get_value(void)
+{
+	return STK_VAL;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief Set the SysTick Clock Source.
+
+The clock source can be either the AHB clock or the same clock divided by 8.
+
+@param[in] clocksource u8. Clock source from @ref systick_clksource.
+*/
+
+void systick_set_clocksource(u8 clocksource)
+{
+	if (clocksource < 2)
+		STK_CTRL |= (clocksource << STK_CTRL_CLKSOURCE_LSB);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief Enable SysTick Interrupt.
+
+*/
+
+void systick_interrupt_enable(void)
+{
+	STK_CTRL |= STK_CTRL_TICKINT;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief Disable SysTick Interrupt.
+
+*/
+
+void systick_interrupt_disable(void)
+{
+	STK_CTRL &= ~STK_CTRL_TICKINT;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief Enable SysTick Counter.
+
+*/
+
+void systick_counter_enable(void)
+{
+	STK_CTRL |= STK_CTRL_ENABLE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief Disable SysTick Counter.
+
+*/
+
+void systick_counter_disable(void)
+{
+	STK_CTRL &= ~STK_CTRL_ENABLE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief SysTick Read the Counter Flag.
+
+The count flag is set when the timer count becomes zero, and is cleared when the
+flag is read.
+
+@returns Boolean if flag set.
+*/
+
+u8 systick_get_countflag(void)
+{
+	if (STK_CTRL & STK_CTRL_COUNTFLAG)
+		return 1;
+	else
+		return 0;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief SysTick Get Calibration Value
+
+@returns Current calibration value
+*/
+u32 systick_get_calib(void)
+{
+	return (STK_CALIB&0x00FFFFFF);
+}
+/**@}*/
+