[STM32L0xx] LowPowerTicker implementation

LowPowerTicker for STM32L0xx family is implemented using the RTC periodic unit
functionality. For more informations please follow this document:

* www.st.com/resource/en/application_note/dm00025071.pdf

Change-Id: Ia4b784a9842971ff4225eccab2938ecba54097be

hal/targets/hal/TARGET_STM/TARGET_STM32L0/lp_ticker.c

@@ -0,0 +1,49 @@
+#include "device.h"
+
+#if DEVICE_LOWPOWERTIMER
+
+#include "ticker_api.h"
+#include "lp_ticker_api.h"
+#include "rtc_api.h"
+#include "rtc_api_hal.h"
+
+static uint8_t lp_ticker_inited = 0;
+static uint32_t m_timestamp = 0;
+static uint32_t m_offset = 0;
+
+void lp_ticker_init() {
+ /*
+ * At this stage we don't have the users requested time.
+ * This is only to cover the API implementation.
+ */
+}
+
+uint32_t lp_ticker_read() {
+ /*
+ * Becuase our RTC has a periodic wake-up timer we just want to simply
+ * return the desired timestamp value to configure RTC exactly with the value
+ * provided by the user and to fulfill the mBed ticker architecture.
+ */
+ return m_timestamp;
+}
+
+void lp_ticker_set_interrupt(timestamp_t timestamp) {
+ m_offset = timestamp;
+
+ if (lp_ticker_inited) return;
+ lp_ticker_inited = 1;
+
+ rtc_periodic_ticker_init(timestamp);
+ rtc_set_irq_handler((uint32_t) lp_ticker_irq_handler);
+}
+
+void lp_ticker_disable_interrupt() {
+ lp_ticker_inited = 0;
+ rtc_periodic_ticker_disable_irq();
+}
+
+void lp_ticker_clear_interrupt() {
+ m_timestamp = m_offset;
+}
+
+#endif

hal/targets/hal/TARGET_STM/TARGET_STM32L0/rtc_api.c

@@ -28,6 +28,9 @@
  *******************************************************************************
  */
 #include "rtc_api.h"
+#include "rtc_api_hal.h"
+#include "stm32l0xx.h"
+#include "stm32l0xx_hal_rtc_ex.h"
 
 #if DEVICE_RTC
 
@@ -38,9 +41,42 @@ static int rtc_inited = 0;
 #endif
 
 static RTC_HandleTypeDef RtcHandle;
+static uint32_t m_synch_prediv;
 
-void rtc_init(void)
+#if DEVICE_LOWPOWERTIMER
+static void (*irq_handler)(void);
+
+static void rtc_calc_periodic_vals(float req_time, uint32_t *periodic_cnt)
+{
+ uint16_t synch_div;
+ float requested_time = (float)(req_time / 1000000);
+ float ck;
+
+ /*
+ * 38000 is LSI typical value. To be measured precisely using a timer input
+ * capture for example.
+ */
+ float freq = (DEVICE_RTC_LSI ? 38000 : LSE_VALUE);
+
+ for (synch_div = 0; synch_div < (int)freq; synch_div++)
+ {
+ ck = freq / ((synch_div + 1.0) * 128.0);
+ *periodic_cnt = ck * requested_time;
+
+ if (*periodic_cnt < 0xFFFF) {
+ break;
+ }
+ }
+ m_synch_prediv = synch_div;
+}
+
+void RTC_IRQHandler()
 {
+ HAL_RTCEx_WakeUpTimerIRQHandler(&RtcHandle);
+}
+#endif
+
+void rtc_init(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;
  uint32_t rtc_freq = 0;
@@ -103,7 +139,12 @@ void rtc_init(void)
 
  RtcHandle.Init.HourFormat = RTC_HOURFORMAT_24;
  RtcHandle.Init.AsynchPrediv = 127;
+#if !DEVICE_LOWPOWERTIMER
  RtcHandle.Init.SynchPrediv = (rtc_freq / 128) - 1;
+#else
+ RtcHandle.Init.SynchPrediv = m_synch_prediv;
+#endif
+
  RtcHandle.Init.OutPut = RTC_OUTPUT_DISABLE;
  RtcHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  RtcHandle.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
@@ -230,4 +271,61 @@ void rtc_write(time_t t)
  HAL_RTC_SetTime(&RtcHandle, &timeStruct, FORMAT_BIN);
 }
 
+#if DEVICE_LOWPOWERTIMER
+void rtc_set_irq_handler(uint32_t handler)
+{
+ irq_handler = (void (*)(void)) handler;
+}
+
+void rtc_periodic_ticker_init(uint32_t timestamp)
+{
+ uint32_t periodic_counter;
+ uint32_t rtcclk;
+ HAL_StatusTypeDef ret;
+
+ /*
+ * For more informations how WakeUp unit values were calculated please follow
+ * this document: www.st.com/resource/en/application_note/dm00025071.pdf
+ */
+ if (timestamp <= 4000000) {
+ periodic_counter = timestamp / 61.035;
+ rtcclk = RTC_WAKEUPCLOCK_RTCCLK_DIV2;
+ m_synch_prediv = 0;
+ } else {
+ rtc_calc_periodic_vals((float)(timestamp), &periodic_counter);
+ rtcclk = RTC_WAKEUPCLOCK_CK_SPRE_16BITS;
+ }
+
+ rtc_init();
+
+ /*
+ * For some reason we need to clear the wakeup time flag to able to start
+ * the RTC periodic unit.
+ */
+ __HAL_RTC_WAKEUPTIMER_CLEAR_FLAG(&RtcHandle, RTC_FLAG_WUTF);
+ ret = HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, periodic_counter - 1, rtcclk);
+
+ if (ret != HAL_OK) {
+ error("SetWakeUpTimer_IT failed!\n");
+ }
+
+ NVIC_SetVector(RTC_IRQn, (uint32_t) &RTC_IRQHandler);
+ HAL_NVIC_EnableIRQ(RTC_IRQn);
+}
+
+void rtc_periodic_ticker_disable_irq()
+{
+ HAL_RTCEx_DeactivateWakeUpTimer(&RtcHandle);
+}
+
+void HAL_RTCEx_WakeUpTimerEventCallback(RTC_HandleTypeDef *hrtc)
+{
+ if (irq_handler)
+ {
+ // Fire the user callback
+ irq_handler();
+ }
+}
+#endif // DEVICE_LOWPOWERTIMER
+
 #endif

hal/targets/hal/TARGET_STM/TARGET_STM32L0/rtc_api_hal.h

@@ -0,0 +1,53 @@
+/* mbed Microcontroller Library
+*******************************************************************************
+* Copyright (c) 2016, STMicroelectronics
+* All rights reserved.
+*
+* Redistribution and use in source and binary forms, with or without
+* modification, are permitted provided that the following conditions are met:
+*
+* 1. Redistributions of source code must retain the above copyright notice,
+* this list of conditions and the following disclaimer.
+* 2. Redistributions in binary form must reproduce the above copyright notice,
+* this list of conditions and the following disclaimer in the documentation
+* and/or other materials provided with the distribution.
+* 3. Neither the name of STMicroelectronics nor the names of its contributors
+* may be used to endorse or promote products derived from this software
+* without specific prior written permission.
+*
+* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*******************************************************************************
+*/
+
+#ifndef MBED_RTC_API_HAL_H
+#define MBED_RTC_API_HAL_H
+
+#include <stdint.h>
+#include "rtc_api.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Extend rtc_api.h
+ */
+void rtc_set_irq_handler(uint32_t handler);
+
+void rtc_periodic_ticker_init(uint32_t timestamp);
+void rtc_periodic_ticker_disable_irq();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif