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Diffstat (limited to 'libopencm3/lib/cm3/systick.c')
| -rw-r--r-- | libopencm3/lib/cm3/systick.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/libopencm3/lib/cm3/systick.c b/libopencm3/lib/cm3/systick.c new file mode 100644 index 0000000..a99593b --- /dev/null +++ b/libopencm3/lib/cm3/systick.c @@ -0,0 +1,203 @@ +/* + * 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 © @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. + * + * @note The systick counter value might be undefined upon startup. To get + * predictable behavior, it is a good idea to set or clear the counter after + * set reload. @seealso systick_clear + * + * @param[in] value uint32_t. 24 bit reload value. + */ + +void systick_set_reload(uint32_t value) +{ + STK_RVR = (value & STK_RVR_RELOAD); +} + +/*---------------------------------------------------------------------------*/ +/** @brief SysTick Read the Automatic Reload Value. + * + * @returns 24 bit reload value as uint32_t. + */ + +uint32_t systick_get_reload(void) +{ + return STK_RVR & STK_RVR_RELOAD; +} + +/** @brief SysTick Set clock and frequency of overflow + * + * This function sets the systick to AHB clock source, and the prescaler to + * generate interrupts with the desired frequency. The function fails, if + * the frequency is too low. + * + * @param[in] freq uint32_t The desired frequency in Hz + * @param[in] ahb uint32_t The current AHB frequency in Hz + * @returns true, if success, false if the desired frequency cannot be set. + */ +bool systick_set_frequency(uint32_t freq, uint32_t ahb) +{ + uint32_t ratio = ahb / freq; + +#if defined(__ARM_ARCH_6M__) + systick_set_clocksource(STK_CSR_CLKSOURCE_AHB); +#else + if (ratio >= (STK_RVR_RELOAD * 8)) { + /* This frequency is too slow */ + return false; + } else if (ratio >= STK_RVR_RELOAD) { + ratio /= 8; + systick_set_clocksource(STK_CSR_CLKSOURCE_AHB_DIV8); + } else { + systick_set_clocksource(STK_CSR_CLKSOURCE_AHB); + } +#endif + systick_set_reload(ratio - 1); + return true; +} + +/*---------------------------------------------------------------------------*/ +/** @brief Get the current SysTick counter value. + * + * @returns 24 bit current value as uint32_t. + */ + +uint32_t systick_get_value(void) +{ + return STK_CVR & STK_CVR_CURRENT; +} + +/*---------------------------------------------------------------------------*/ +/** @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 uint8_t. Clock source from @ref systick_clksource. + */ + +void systick_set_clocksource(uint8_t clocksource) +{ + STK_CSR = (STK_CSR & ~STK_CSR_CLKSOURCE) | + (clocksource & STK_CSR_CLKSOURCE); +} + +/*---------------------------------------------------------------------------*/ +/** @brief Enable SysTick Interrupt. + * + */ + +void systick_interrupt_enable(void) +{ + STK_CSR |= STK_CSR_TICKINT; +} + +/*---------------------------------------------------------------------------*/ +/** @brief Disable SysTick Interrupt. + * + */ + +void systick_interrupt_disable(void) +{ + STK_CSR &= ~STK_CSR_TICKINT; +} + +/*---------------------------------------------------------------------------*/ +/** @brief Enable SysTick Counter. + * + */ + +void systick_counter_enable(void) +{ + STK_CSR |= STK_CSR_ENABLE; +} + +/*---------------------------------------------------------------------------*/ +/** @brief Disable SysTick Counter. + * + */ + +void systick_counter_disable(void) +{ + STK_CSR &= ~STK_CSR_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. + */ + +uint8_t systick_get_countflag(void) +{ + return (STK_CSR & STK_CSR_COUNTFLAG) ? 1 : 0; +} + +/*---------------------------------------------------------------------------*/ +/** @brief SysTick Clear counter Value. + * + * The counter value is cleared. Useful for well defined startup. + */ + +void systick_clear(void) +{ + STK_CVR = 0; +} + +/*---------------------------------------------------------------------------*/ +/** @brief SysTick Get Calibration Value + * + * @returns Current calibration value + */ +uint32_t systick_get_calib(void) +{ + return STK_CALIB & STK_CALIB_TENMS; +} +/**@}*/ + |