Generate device EUI from MAC

include/TheThingsNetwork.h

@@ -104,6 +104,32 @@ public:
      */
     bool provision(const char *devEui, const char *appEui, const char *appKey);
 
+    /**
+     * @brief Sets the information needed to activate the device via OTAA, using the MAC to generate the device EUI
+     * and without actually activating.
+     * 
+     * The generated device EUI and the provided app EUI and app key are saved in non-volatile memory. Before
+     * this function is called, 'nvs_flash_init' must have been called once.
+     * 
+     * The device EUI is generated by retrieving the ESP32's WiFi MAC address and expanding it into a device EUI
+     * by adding FFFE in the middle. So the MAC address A0:B1:C2:01:02:03 becomes the EUI A0:B1:C2:FF:FE:01:02:03.
+     * The TTN console requires the device EUI in MSB format, so it has to be reversed and entered as
+     * "03 02 01 FE FF C2 B1 A0".
+     * 
+     * Generating the device EUI from the MAC address allows to flash the same app EUI and app key to a batch of
+     * devices. However, using the same app key for multiple devices is insecure. Only use this approach if
+     * it is okay for that the LoRa communication of your application can easily be intercepted and that
+     * forged data can be injected.
+     * 
+     * Call join() without arguments to activate.
+     * 
+     * @param appEui  Application EUI of the device (16 character string with hexadecimal data)
+     * @param appKey  App Key of the device (32 character string with hexadecimal data)
+     * @return true   if the provisioning was successful
+     * @return false  if the provisioning failed
+     */
+    bool provisionWithMAC(const char *appEui, const char *appKey);
+
     /**
      * @brief Start task that listens on configured UART for provisioning commands.
      *