new sketch basic with lowPower deepSleep and send packet on wakeup

This example is configuring the stm32WL for LoraWan connection and
low power mode.
After LoraWan is connected, it periodically goes to low power
deep sleep mode (stop 2) and wakes Up to send a packet

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

examples/LowPowerBasic/LowPowerBasic.ino

@@ -0,0 +1,116 @@
+/*
+ *  LowPowerBasic
+ *
+ * This is a basic example that demonstrates how to configure the
+ * library, join the network, then go to Low Power deep Sleep (STOP mode)
+ * and on WakeUp, send regular packets with current RTC calendar value.
+ * Then It goes to LowPower again for a period (TX_INTERVAL milliseconds)
+ *
+ * This example is using the RTC in MIX (binary and BCD) mode
+ * and the LowPower library
+ *
+ * Revised BSD License - https://spdx.org/licenses/BSD-3-Clause.html
+ */
+#include <STM32LoRaWAN.h>
+#include <STM32LowPower.h>
+#include <STM32RTC.h>
+
+STM32LoRaWAN modem;
+/* Get the rtc object */
+STM32RTC& rtc = STM32RTC::getInstance();
+
+/* Change this value to set alarm match offset in millisecond */
+static const unsigned long TX_INTERVAL = 60000; /* ms */
+
+// Declare it volatile since it's incremented inside an interrupt
+volatile int alarmMatch_counter = 0;
+
+/* callback function once the Alarm A matched */
+void alarmMatch(void* data)
+{
+  UNUSED(data);
+  alarmMatch_counter++;
+}
+
+void background_work()
+{
+  /* Toggle LED */
+  digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
+
+  Serial.print("  Alarm Match: ");
+  Serial.print(alarmMatch_counter);
+  Serial.println(" times. deepSleeping now ! ");
+  Serial.flush(); /* Flush before going to sleep */
+}
+
+void setup() {
+  pinMode(LED_BUILTIN, OUTPUT);
+
+  Serial.begin(115200);
+  Serial.println("Start");
+  modem.begin(EU868);
+
+  // Configure join method by (un)commenting the right method
+  // call, and fill in credentials in that method call.
+
+  bool connected = modem.joinOTAA(/* AppEui */ "0000000000000000", /* AppKey */ "00000000000000000000000000000000", /* DevEui */ "0000000000000000");
+  //bool connected = modem.joinABP(/* DevAddr */ "00000000", /* NwkSKey */ "00000000000000000000000000000000", /* AppSKey */ "00000000000000000000000000000000");
+
+
+  if (connected) {
+    Serial.println("Joined");
+  } else {
+    Serial.println("Join failed");
+    while (true); /* infinite loop */
+  }
+
+  /* set the calendar */
+  rtc.setTime(15, 30, 58);
+  rtc.setDate(4, 9, 23);
+
+  // Configure low power
+  LowPower.begin();
+  LowPower.enableWakeupFrom(&rtc, alarmMatch);
+
+}
+
+void send_packet() {
+  char payload[27] = { 0 }; /* packet to be sent */
+  /* prepare the Tx packet : get date and format string */
+  sprintf(payload, "%02d/%02d/%04d - %02d:%02d:%02d",
+          rtc.getMonth(), rtc.getDay(), 2000 + rtc.getYear(),
+          rtc.getHours(), rtc.getMinutes(), rtc.getSeconds());
+  modem.setPort(10);
+  modem.beginPacket();
+  modem.write(payload, strlen(payload));
+Serial.println(payload);
+  if (modem.endPacket() == (int)strlen(payload)) {
+    Serial.println("Sent packet");
+  } else {
+    Serial.println("Failed to send packet");
+  }
+
+  if (modem.available()) {
+    Serial.print("Received packet on port ");
+    Serial.print(modem.getDownlinkPort());
+    Serial.print(":");
+    while (modem.available()) {
+      uint8_t b = modem.read();
+      Serial.print(" ");
+      Serial.print(b >> 4, HEX);
+      Serial.print(b & 0xF, HEX);
+    }
+    Serial.println();
+  }
+}
+
+void loop()
+{
+
+  background_work();
+
+  LowPower.deepSleep(TX_INTERVAL);
+
+  send_packet();
+
+}