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152 lines
4.3 KiB
152 lines
4.3 KiB
/** @addtogroup iwdg_file IWDG peripheral API
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@ingroup peripheral_apis
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@author @htmlonly © @endhtmlonly 2012 Ken Sarkies ksarkies@internode.on.net
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This library supports the Independent Watchdog Timer System in the STM32F1xx
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series of ARM Cortex Microcontrollers by ST Microelectronics.
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The watchdog timer uses the LSI (low speed internal) clock which is low power
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and continues to operate during stop and standby modes. Its frequency is
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nominally 32kHz (40kHz for the STM32F1xx series) but can vary from as low
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as 17kHz up to 60kHz (refer to datasheet electrical characteristics).
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Note that the User Configuration option byte provides a means of automatically
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enabling the IWDG timer at power on (with counter value 0xFFF). If the
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relevant bit is not set, the IWDG timer must be enabled by software.
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@note: Tested: CPU STM32F103RET6, Board ET-ARM Stamp STM32
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*/
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/*
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* This file is part of the libopencm3 project.
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**@{*/
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#include <libopencm3/stm32/iwdg.h>
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#define LSI_FREQUENCY 32000
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#define COUNT_LENGTH 12
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#define COUNT_MASK ((1 << COUNT_LENGTH)-1)
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/*---------------------------------------------------------------------------*/
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/** @brief IWDG Enable Watchdog Timer
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The watchdog timer is started. The timeout period defaults to 512 milliseconds
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unless it has been previously defined.
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*/
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void iwdg_start(void)
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{
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IWDG_KR = IWDG_KR_START;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief IWDG Set Period in Milliseconds
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The countdown period is converted into count and prescale values. The maximum
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period is 32.76 seconds; values above this are truncated. Periods less than 1ms
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are not supported by this library.
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A delay of up to 5 clock cycles of the LSI clock (about 156 microseconds)
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can occasionally occur if the prescale or preload registers are currently busy
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loading a previous value.
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@param[in] period uint32_t Period in milliseconds (< 32760) from a watchdog
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reset until a system reset is issued.
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*/
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void iwdg_set_period_ms(uint32_t period)
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{
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const int PRESCALER_MAX = 6;
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uint8_t prescale = 0;
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/* Set the count to represent ticks of 8kHz clock (the 32kHz LSI clock
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* divided by 4 = lowest prescaler setting)
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*/
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uint32_t count = period << 3;
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/* Prevent underflow */
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if (count == 0) {
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count = 1;
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}
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/* Shift count while increasing prescaler as many times as needed to
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* fit into IWDG_RLR
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*/
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while ((count - 1) >> COUNT_LENGTH) {
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count >>= 1;
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prescale++;
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}
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/* IWDG_RLR actually holds count - 1 */
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count--;
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/* Clamp to max possible period */
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if (prescale > PRESCALER_MAX) {
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count = COUNT_MASK;
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prescale = PRESCALER_MAX;
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}
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while (iwdg_prescaler_busy());
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IWDG_KR = IWDG_KR_UNLOCK;
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IWDG_PR = prescale;
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while (iwdg_reload_busy());
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IWDG_KR = IWDG_KR_UNLOCK;
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IWDG_RLR = count & COUNT_MASK;
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/* Refresh counter after configuration is complete */
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iwdg_reset();
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}
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/*---------------------------------------------------------------------------*/
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/** @brief IWDG Get Reload Register Status
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@returns boolean: TRUE if the reload register is busy and unavailable for
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loading a new count value.
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*/
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bool iwdg_reload_busy(void)
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{
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return IWDG_SR & IWDG_SR_RVU;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief IWDG Get Prescaler Register Status
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@returns boolean: TRUE if the prescaler register is busy and unavailable for
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loading a new period value.
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*/
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bool iwdg_prescaler_busy(void)
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{
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return IWDG_SR & IWDG_SR_PVU;
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}
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/*---------------------------------------------------------------------------*/
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/** @brief IWDG reset Watchdog Timer
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The watchdog timer is reset. The counter restarts from the value in the reload
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register.
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*/
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void iwdg_reset(void)
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{
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IWDG_KR = IWDG_KR_RESET;
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}
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/**@}*/
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