add new sketch for RTC running in BINary mode with Alarm

This examples is configuring the RTC in BIN mode (binary only)
and sets Alarm A & B (if exists) a few ms after the current time.

Signed-off-by: Francois Ramu <francois.ramu@st.com>

Author: FRASTM

examples/bin_onlyRTCAlarm/bin_onlyRTCAlarm.ino

@@ -0,0 +1,83 @@
+/*
+  mode BINary only RTC alarm
+
+  This sketch shows how to configure the alarm A & B of the RTC in BIN mode
+
+  Creation 12 Dec 2017
+  by Wi6Labs
+  Modified 03 Jul 2020
+  by Frederic Pillon for STMicroelectronics
+  Modified 03 sept 2023
+  by Francois Ramu for STMicroelectronics
+
+  This example code is in the public domain.
+
+  https://github.com/stm32duino/STM32RTC
+*/
+
+#include <STM32RTC.h>
+
+/* Get the rtc object */
+STM32RTC& rtc = STM32RTC::getInstance();
+
+uint32_t timeout;
+
+void setup()
+{
+  Serial.begin(115200);
+
+  // Select RTC clock source: LSI_CLOCK, LSE_CLOCK or HSE_CLOCK.
+  rtc.setClockSource(STM32RTC::LSE_CLOCK);
+
+  /* Configure the RTC mode */
+  rtc.setBinaryMode(STM32RTC::MODE_BIN);
+
+  /* in BIN mode time and Date register are not used, only the subsecond register for milisseconds */
+  rtc.begin(true, STM32RTC::HOUR_24);
+
+  /* wait for a while */
+  delay(200);
+
+  /* subsecond expressed in milliseconds */
+  Serial.printf("Start at %d ms \r\n", rtc.getSubSeconds());
+
+  /* Attach the callback function before enabling Interrupt */
+  rtc.attachInterrupt(alarmAMatch);
+
+  /* Program the AlarmA in 12 seconds */
+  rtc.setAlarmTime(0, 0, 0, 12000);
+  rtc.enableAlarm(rtc.MATCH_SUBSEC);
+  Serial.printf("Set Alarm A in 12s (at %d ms)\r\n", rtc.getAlarmSubSeconds());
+
+#ifdef RTC_ALARM_B
+  /* Program ALARM B in 400ms ms from now (keep timeout < 1000ms) */
+  timeout = rtc.getSubSeconds() + 400;
+
+  rtc.attachInterrupt(alarmBMatch, STM32RTC::ALARM_B);
+  rtc.setAlarmSubSeconds(timeout, STM32RTC::ALARM_B);
+  rtc.enableAlarm(rtc.MATCH_SUBSEC, STM32RTC::ALARM_B);
+  Serial.printf("Set Alarm B (in %d ms) at %d ms\r\n", 400,
+  rtc.getAlarmSubSeconds(STM32RTC::ALARM_B));
+#endif
+
+}
+
+void loop()
+{
+
+}
+
+void alarmAMatch(void *data)
+{
+  UNUSED(data);
+  rtc.disableAlarm(STM32RTC::ALARM_A);
+  Serial.printf("Alarm A Match at %d ms \r\n", rtc.getSubSeconds());
+}
+
+void alarmBMatch(void *data)
+{
+  UNUSED(data);
+  rtc.disableAlarm(STM32RTC::ALARM_B); /* Else it will trig again */
+  Serial.printf("Alarm B Match at %d ms\r\n", rtc.getSubSeconds());
+}
+