reflow-oven-control-sw/stm-firmware/safety/watchdog.c

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/* Reflow Oven Controller
*
* Copyright (C) 2020 Mario Hüttel <mario.huettel@gmx.net>
*
* This file is part of the Reflow Oven Controller Project.
*
* The reflow oven controller is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* The Reflow Oven Control Firmware 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with the reflow oven controller project.
* If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @addtogroup watchdog
* @{
*/
#include <reflow-controller/safety/watchdog.h>
#include <stm32/stm32f4xx.h>
/**
* @brief This key is expected by hardware to be written to the IWDG_KR register in order to reset the watchdog
*/
#define STM32_WATCHDOG_RESET_KEY 0xAAAA
/**
* @brief This key is expected by hardware to be written to the IWDG_KR register in order to enable the watchdog
*/
#define STM32_WATCHDOG_ENABLE_KEY 0xCCCC
/**
* @brief This key is expected by hardware to be written to the IWDG_KR register in order to enable access to config
* registers
*/
#define STM32_WATCHDOG_REGISTER_ACCESS_KEY 0x5555
int watchdog_setup(uint8_t prescaler)
{
uint32_t prescaler_reg_val;
/** - Activate the LSI oscillator */
RCC->CSR |= RCC_CSR_LSION;
__DSB();
/** - Wait for the oscillator to be ready */
while (!(RCC->CSR & RCC_CSR_LSIRDY));
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if (prescaler == 4U)
prescaler_reg_val = 0UL;
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else if (prescaler == 8U)
prescaler_reg_val = 1UL;
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else if (prescaler == 16U)
prescaler_reg_val = 2UL;
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else if (prescaler == 32U)
prescaler_reg_val = 3UL;
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else if (prescaler == 64U)
prescaler_reg_val = 4UL;
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else if (prescaler == 128U)
prescaler_reg_val = 5UL;
else
prescaler_reg_val = 6UL;
/** - Unlock registers */
IWDG->KR = STM32_WATCHDOG_REGISTER_ACCESS_KEY;
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/** - Wait until prescaler can be written */
while (IWDG->SR & IWDG_SR_PVU);
/** - Write prescaler value */
IWDG->PR = prescaler_reg_val;
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/* - Wait until reload value can be written */
while (IWDG->SR & IWDG_SR_RVU);
/** - Set reload value fixed to 0xFFF */
IWDG->RLR = 0xFFFU;
/** - Write enable key */
IWDG->KR = STM32_WATCHDOG_ENABLE_KEY;
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/** - Do a first reset of the counter. This also locks the config regs */
watchdog_ack(WATCHDOG_MAGIC_KEY);
return 0;
}
int watchdog_ack(uint32_t magic)
{
int ret = -1;
/** - Check if magic key is correct */
if (magic == WATCHDOG_MAGIC_KEY) {
/** - Write reset key to watchdog */
IWDG->KR = STM32_WATCHDOG_RESET_KEY;
ret = 0;
}
return ret;
}
/** @} */