chare(examples): configure RTC alarm in BIN mode to wakeup from sleep

In this sketch the RTC is configured in BINary only mode
(for the stm32 devices that supports it)
An Alarm A is set to wakeup the system from low power
deep sleep.

Signed-off-by: Francois Ramu <[email protected]>

Author: FRASTM

examples/binAlarmTimedWakeup/binAlarmTimedWakeup.ino

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+/*
+  binAlarmTimedWakeup
+
+  This sketch demonstrates the usage of Internal Interrupts to wakeup a chip in deep sleep mode.
+  when the RTC is configured in BINary mode (BIN_ONLY)
+
+  In this sketch:
+  - RTC in BINARY only for the stm32 that supports this mode
+  - Alarm is set to wake up the processor each 'atime' and called a custom alarm callback
+  which increment a value and reload alarm with 'atime' offset.
+
+  This example code is in the public domain.
+*/
+
+#include "STM32LowPower.h"
+#include <STM32RTC.h>
+
+/* Get the rtc object */
+STM32RTC& rtc = STM32RTC::getInstance();
+
+/* Change this value to set alarm match offset in millisecond */
+static uint32_t atime = 600;
+static uint32_t time_ts; /* value to get the binary time */
+
+// Declare it volatile since it's incremented inside an interrupt
+volatile int alarmMatch_counter = 0;
+
+void setup() {
+  // Select RTC clock source: LSI_CLOCK, LSE_CLOCK or HSE_CLOCK.
+  // By default the LSI is selected as source.
+  // rtc.setClockSource(STM32RTC::LSE_CLOCK);
+  // Select the STM32RTC::MODE_BIN
+  rtc.setBinaryMode(STM32RTC::MODE_BIN);
+  rtc.begin(true); /* reset the RTC else the mode is not changed */
+
+  pinMode(LED_BUILTIN, OUTPUT);
+
+  Serial.begin(115200);
+  while (!Serial) {}
+  Serial.println(" Start !");
+
+  // Configure low power
+  LowPower.begin();
+  LowPower.enableWakeupFrom(&rtc, alarmMatch, &atime);
+
+  rtc.getEpoch(&time_ts);
+
+  // Configure first alarm in 2 seconds then it will be done in the rtc callback
+  rtc.setAlarmEpoch(0, STM32RTC::MATCH_SUBSEC, (time_ts + 2000), STM32RTC::ALARM_A);
+}
+
+void loop() {
+  Serial.print("Alarm Match: ");
+  Serial.print(alarmMatch_counter);
+  Serial.println(" times.");
+  Serial.flush();
+  digitalWrite(LED_BUILTIN, HIGH);
+  LowPower.deepSleep();
+  digitalWrite(LED_BUILTIN, LOW);
+  LowPower.deepSleep();
+}
+
+void alarmMatch(void* data) {
+  // This function will be called once on device wakeup
+  // You can do some little operations here (like changing variables which will be used in the loop)
+  // Remember to avoid calling delay() and long running functions since this functions executes in interrupt context
+  uint32_t _millis = 1000;
+
+  if (data != NULL) {
+    _millis = *(uint32_t*)data;
+  }
+
+  rtc.getEpoch(&time_ts);
+  alarmMatch_counter++;
+  rtc.setAlarmEpoch(0, STM32RTC::MATCH_SUBSEC, (time_ts + _millis), STM32RTC::ALARM_A);
+}