Implement the BD_ADDR(char * address_string) constructor. (#1440)

* Implement the BD_ADDR(char * address_string) constructor.

* Updating implementation to use sscanf.

There is an extra step after the sscanf that checks that we got
six bytes back and if we did not, it will set all bytes in the
address to zero.

* Example using BD_ADDR(const char * address_string)

This example shows how BD_ADDR(const char * address_string) can
be used to create BD_ADDR objects to use for comparisons etc.

* Update LEDeviceScanner.ino formatting

libraries/BTstackLib/examples/LEDeviceScanner/LEDeviceScanner.ino

+#include <BTstackLib.h>
+#include <SPI.h>
+
+/*
+   EXAMPLE_START(LEDeviceScanner): LE Device Scanner
+
+   @text The LE Device Scanner monitors BLE device advertisements,
+   keeping track of one or more known devices as they appear.
+*/
+
+// Application state
+int counter[2] = {0, 0};
+BD_ADDR known_devices[2] = {BD_ADDR("DB:88:B6:70:9E:EB"),
+                            BD_ADDR("C9:60:BD:F2:B4:9D")
+                           };
+
+/*
+   @section Setup
+
+   @text After BTstack.setup(), BTstack is configured to call
+   advertisementCallback whenever an Advertisement was received.
+*/
+/* LISTING_START(LEDeviceScannerSetup): LE Device Scanner Setup */
+void setup(void) {
+  Serial.begin(9600);
+  BTstack.setBLEAdvertisementCallback(advertisementCallback);
+  BTstack.setup();
+  BTstack.bleStartScanning();
+}
+/* LISTING_END(LEDeviceScannerSetup): LE Device Scanner Setup */
+
+/*
+   @section Loop
+
+   @text In the standard Arduino loop() function, BTstack's loop() is called.
+*/
+/* LISTING_START(LEDeviceScannerLoop): Loop */
+void loop(void) {
+  BTstack.loop();
+}
+/* LISTING_END(LEDeviceScannerLoop): Loop */
+
+/*
+   @section Advertisement Callback
+
+   @text Whenever an Advertisement is received, isIBeacon() checks if
+   it contains an iBeacon.
+
+   If it's not an iBeacon, the BD_ADDR is compared to the address we are
+   looking for and the counter is incremented.
+*/
+/* LISTING_START(LEDeviceScannerAdvertisementCallback): Advertisement Callback
+*/
+void advertisementCallback(BLEAdvertisement *bleAdvertisement) {
+  if (!(bleAdvertisement->isIBeacon())) {
+    Serial.print("Device discovered: ");
+    Serial.println(bleAdvertisement->getBdAddr()->getAddressString());
+    for (size_t i = 0; i < sizeof(counter) / sizeof(int); i++) {
+      if (memcmp(bleAdvertisement->getBdAddr()->getAddress(),
+                 known_devices[i].getAddress(), sizeof(known_devices[i])) == 0) {
+        counter[i]++;
+        Serial.printf("Known device: %s, has been discovered %d times.\n",
+                      known_devices[i].getAddressString(), counter[i]);
+      }
+    }
+  }
+}
+/* LISTING_END(LEDeviceScannerAdvertisementCallback): Advertisement Callback */

libraries/BTstackLib/src/BTstackLib.cpp

@@ -396,9 +396,13 @@ BD_ADDR::BD_ADDR(void) {
 }
 
 BD_ADDR::BD_ADDR(const char * address_string, BD_ADDR_TYPE address_type) : address_type(address_type) {
-    (void) address_string;
-    // TODO: implement
-    // log_error("BD_ADDR::BD_ADDR(const char *, BD_ADDR_TYPE) not implemented yet!");
+    int processed = sscanf(address_string, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx", address, address + 1,
+                           address + 2, address + 3, address + 4, address + 5);
+    if (processed != 6) { // Set address to zeroes if we did not get six bytes back.
+        for (int i = 0; i < 6; i++) {
+            address[i] = 0;
+        }
+    }
 }
 
 BD_ADDR::BD_ADDR(const uint8_t address[6], BD_ADDR_TYPE address_type) : address_type(address_type) {