NOTE!

__This repository will no longer be maintained as the nRF5 SDK for Eddystone is now part of nRF5 SDK version 13.0.0.__

The project is found in the folder examples/ble_peripheral/ble_app_eddystone

Note that this version only supports nRF52 support.

Experimental support for nRF51 is found in nRF5 SDK Version 12.2.0 A future 12.x release will add production quality support for nRF51 for Eddystone.

nRF5 SDK for Eddystone™

This is an example implementation of the Eddystone GATT Configuration Service for nRF52. Support for nRF51 is scheduled for a future release. The application is intended to be used together with the open source nRF Beacon for Eddystone Android App. It is recommended to read the official specification for Eddystone, an open beacon format from Google to get a thorough understanding. Go to Quick start if you want to experiment right away.

Table of contents

• Release note
• Introduction
• Supported characteristics
• Requirements
• Known issues
• How to install
• How to use
• How it works
• Issues and support
• Third-party crypto libraries
• About
• License

Release note

• v0.7.1 (may 4 2016)

  • NEW! Support for SEGGER Embedded Studio, a cross-platform firmware IDE for OSX, Windows and Linux! Great for developers who do not own a Keil license or is developing on OSX/Linux.
  • Monitor Mode Debugging enabled by default in Embedded Studio. This allows breakpoints to be taken while high priority interrupts can still be serviced (i.e. BLE connections will not be lost while halted).

• v0.7 (April 29 2016)

  • Added persistent slot configurations feature so that after power loss or intentional reset of the chip, all previously configured slots will be restored from flash memory. Note that in order for slots to be saved to flash memory, a BLE Disconnect event must occur before any accidental or intentional power loss.
  • EID clock values are now written to flash memory every 24 hours as recommended by Google's spec for recovering from power loss regarding EID computation.
  • Merged in via script the cifra crypto library's fix for a known issue with EAX encryption of the eTLM frames. Now eTLM frames are properly encrypted. Make sure to run crypto_setup_all.sh so the correct commits are checked out.
  • Added a stand-alone application hex file without the softdevice merged in so it can be DFUed with a bootloader.
  • Other small stability improvements, bug fixes, and house cleaning.
  • Updated README with How it works section explaining the different modules in the firmware.

• v0.6 (April 21 2016)

  • Revamped folder structures and project setup procedure to allow for better user setup experience. Namely the downloading of SDK via scripts. Details described below in How to install.
  • Merged in cifra crypto library's fix for a known issue with EAX encryption of the eTLM frames. Now eTLM frames are properly encrypted.
  • Fixed a bug with the EID slot 4-byte clock being slow.
  • Added scan response capability when the beacon is put into connectable mode which contains nRF5_Eddy as the device name and the Eddystone Configuration GATT Service UUID a3c87500-8ed3-4bdf-8a39-a01bebede295 as the UUID in the scan response packet, as recommended by the latest spec from Google.
  • Improved LED Indication for different beacon states: Advertising, Advertising in connectable mode, Connected. Details below in How to use.
  • Improved connection stability with "Error 133" commonly seen on Samsungs by adding the Peripheral Preferred Connection Parameters characteristic

• v0.5 (April 15 2016)

  • First public release

Introduction

The new Eddystone GATT Configuration Service enables simple configuration of beacons. The user can configure the beacon to broadcast all Eddystone frame types:

• Eddystone-URL
• Eddystone-UID
• Eddystone-EID
• Eddystone-TLM
• Eddystone-eTLM

Currently the firmware has five available slots and each slot can be configured to any of the unique frame types. From the source code it is possible to increase or decrease the number of available slots.

In addition to the new Eddystone GATT Configuration Service there are also two new frame types aimed at secure use cases.

The new frame types are Eddystone-EID and Eddystone-eTLM. EID, or Ephemeral Identifier, is a secure version of UID. eTLM, or encrypted TLM, is a secure telemetry format and provides information on the health of a beacon.

Eddystone-EID and Eddystone-eTLM protect against spoofing, replay attacks and malicious asset tracking - which are known beacon vulnerabilities.

Spoofing

Impersonating Eddystone-EIDs is difficult since the advertising data is encrypted and regularly updated.

Replay Attacks

By randomizing and never sending the Unlock Key in clear text it is difficult to perform replay attacks with the new Eddystone GATT Configuration Service. The beacon creates a random challenge token every time a user tries to unlock it. The user then encrypts the Lock Key with the challenge token and sends the result to the beacon. The result will be different for every unlock and replay attacks are therefore impossible.

Malicious Asset Tracking

Eddystone-EIDs randomize the device ID of the beacon as well as the encrypted advertising data. Since there are no constant values to track it will be difficult if not impossible to track the location of a single beacon over any significant time period.

IMPORTANT In order to have all the security benefits of Eddystone-EID and Eddystone-eTLM refrain from configuring other non-secure frame types while broadcasting these secure frame types

Supported characteristics

The application supports all functionality of the Eddystone GATT Configuration Service except the advanced optional characteristics as displayed in the table below. The advanced characteristics will be implemented in a future release.

Prerequisites

Software

• Keil uVision 5 IDE (Note: you must have a registered version of Keil in order to compile source code that generates more than 32kB of code and data, currently this project generates 39 kB even with -O3 optimization level).
• SEGGER Embedded Studio IDE (Note: If you don't have a Keil license or you are developing on Mac OS X or Linux this is the best option).
• Git Bash.
• nRFgo Studio (Note: Not required if using SEGGER Embedded Studio).

The application might work with other versions of the SDK/Keil but some modification of the source code is likely required on your part. For a quick start on using Embedded Studio with nRF5 devices see: https://devzone.nordicsemi.com/blogs/845/segger-embedded-studio-cross-platform-ide-w-no-cod/.

Hardware

• nRF52 Development Kit
• Android phone 4.3+

Known issues

• IAR and GCC Makefile based projects are scheduled for a future release.
• When compiling in Keil (ARMCC) there are warnings from the third-party crypto libraries.

How to install

Quick start

This is the recommended approach if you just want to get started quickly without building the project yourself.

• Connect the nRF52 DK to your computer. It will show up as a JLINK USB drive.

• Download the nrf5_sdk_for_eddystone_v0.7.hex file in the hex folder in this repository.

• Drag and drop the nrf5_sdk_for_eddystone_v0.7.hex file on the JLINK drive to automatically program the nRF52 DK.

• Install the nRF Beacon for Eddystone Android App from Play Store.

• Follow the instructions on how to use the App.

Compile from source

• Clone this repository into your preferred location (keep it close to root to avoid path too long problem on Windows, because the SDK will be downloaded via a script into the same parent directory as well)

  git clone https://github.com/NordicPlayground/nrf5-sdk-for-eddystone.git

• In the nrf5-sdk-for-eddystone\setup_scripts folder, you will find several bash/batch scripts that will help you set up the repository with the necessary components in order for Keil to compile the project. The 2 scripts that are of interest to the user are download_sdk_setup.sh and existing_sdk_setup.sh:

  • Run the download_sdk_setup.sh script if you don't already have nRF5_SDK_11.0.0_89a8197. This script will automatically download the required nRF5 SDK into the parent folder ( so that nRF5_SDK_11.0.0_89a8197 lives right next to nrf5-sdk-for-eddystone), create necessary symlinks into the SDK for Keil to find the required components, and also clone the required third party crypto libraries from Github.
  • If you already have nRF5_SDK_11.0.0_89a8197 on your machine, then simply open existing_sdk_setup.sh in your favourite text editor and edit the line

    export SDK_PATH=""

    and fill in the absolute path to your existing SDK folder, as such:

    e.g. SDK_PATH="C:/example_path/nRF5_SDK_11.0.0_89a8197"

    then save it and run the script. It will do the same things as the download_sdk_setup.sh, except not downloading the SDK of course.

• If everything goes smoothly, you should find the following additional components in the nrf5-sdk-for-eddystone, indicated with ** :

  Some_parent_folder
      nRF5_SDK_11.0.0_89a8197 (would be here if you ran download_sdk_setup.sh)
      nrf5-sdk-for-eddystone
                              bsp
                              hex
                              include
                              project
                            **sdk_components
                            **sdk_external
                              setup_scripts
                              source
                                   ble_services
                                 **crypto_libs
                                   modules
                              .gitignore
                              licenses.txt
                              README.md

Keil

• Open the .uvprojx project file in Keil, which is found here:

  nrf5-sdk-for-eddystone\project\pca10040_s132\arm5_no_packs

• The project is expected to compile with 2 warnings coming from one of the crypto libraries when using Keil. You might also need to download NordicSemiconductor::nRF_DeviceFamilyPack 8.5.0 in Keil's Pack Installer if you don't already have it before the project can compile.
• Before loading the firmware onto your nRF52 DK or starting a debug session in Keil, you must flash in the S132 Softdevice that can be found here:

  sdk_components\softdevice\s132\hex\s132_nrf52_2.0.0_softdevice.hex

  The Softdevice can be flashed in with Nordic's nRFgo Studio tool. For instructions on how to use nRFgo Studio, follow the tutorial here under the Preparing the Development Kit section.

SEGGER Embedded Studio

• Open the .emProject project file in SEGGER Embedded Studio, which is found here:

  nrf5-sdk-for-eddystone\project\pca10040_s132\embedded_studio

• Manually install the nRF device family pack by downloading it here, and in Embedded Studio go to Tools->Packages->Manually install packages, and select it. Install the CMSIS-CORE Support Package by going to Tools->Package Manager, and double clicking it.
• Currently there is a bug in our SDK when compiling with GCC. In 'app_util_platform.h' you need to replace:

  #define PACKED(TYPE) __packed TYPE // This should be line 87.

  with this:

  #if defined(__CC_ARM)
  #define PACKED(TYPE) __packed TYPE
  #elif defined(__ICCARM__)
  #define PACKED(TYPE) __packed TYPE
  #else
  #define PACKED(TYPE) TYPE __attribute__((packed))
  #endif

• Build and run/debug the project.

Debugging

• Monitor Mode Debugging is enabled in Embedded Studio by default (can easily be added in Keil, IAR).
• Make sure DebugMon_Handler is defined in your system's startup files (This is done in recent releases but your system files could be old).

How to use

After flashing the firmware to a nRF52 DK it will automatically start broadcasting a Eddystone-URL pointing to http://www.nordicsemi.com, with LED 1 blinking. In order to configure the beacon to broadcast a different URL or a different frame type it is necessary to put the DK in configuration mode by pressing Button 1 on the DK so it starts advertising in "Connectable Mode". After that, it can be connected to nRF Beacon for Eddystone app, which allows the writing of the Lock Key to the Unlock Characteristic.

Please note that after pressing Button 1, the DK will only broadcast in "Connectable Mode" for 1 minute. After which, you must press Button 1 again if you did not manage to connect in time with the App.

LED Indications:

Detailed instructions on how to use the App is available in the nRF Beacon for Eddystone GitHub repository.

How it works

Modules

The firmware is mainly broken up in several modules that each handle specific functionalities required by the Eddystone specification.

• eddystone_ble_handler

  • Here is where the BLE functionalities are initialized along with all the other modules in the firmware. It's essentially the practical main file of the project.
  • In services_and_modules_init you can see how the broadcast capabilities are set via the ble_ecs_init_params_t struct and can change the defined macros (prefixed with APP_) accordingly in eddystone_app_config.h to reflect your needs.
  • The module is also responsible for handling all BLE events coming from the softdevice and dispatching them to the other modules that need them.
  • Most importantly this module controls all the R/W authorizations of the Eddystone Configuration GATT Service. Any characteristic R/W events coming from the Central is handled here in ecs_read_evt_handler() and ecs_write_evt_handler() so the correct per slot information and security information can be accessed in the eddystone_adv_slot and eddystone_security modules before R/W of the characteristic values.

• eddystone_adv_slot

  • This module is the data core of the firmware which contains all the data (non-security related) in the slots with which the BLE Central interact.

  Essentially this module contains an array of eddystone_adv_slot_t structures, with each structure representing a slot: parameters such as the advertising interval and radio tx power are written to and retrieved from here, and it's also responsible for formating and keeping the data of the actual frames (adv_frame member of the struct) to be broadcast (which are retrieved and advertised by the eddystone_advertising_manager) or to be read from R/W ADV Slot characteristic. The exception is for TLMs/eTLMs which is generated in real-time by eddystone_tlm_manager's eddystone_tlm_manager_tlm_get()/eddystone_tlm_manager_etlm_get()every time the eddystone_advertising_manager needs to broadcast a TLM/eTLM and the advertised packet is copied back into the slot's adv_frame via a pointer so that when the user reads it in characteristic 10, the last advertised packet will be displayed.

• eddystone_security

  • The security module does exactly what it sounds like it does, security. All the encryption/decryption processes such as validating the unlock key, generating and exchanging ECDH keys, eTLM encryption etc. are handled here here and it acts as an abstraction layer to the 3rd party crypto libraries that we use. Similar to eddystone_adv_slot, the security module contains an array of eddystone_security_slot_t structures that contain all the necessary data to maintain an EID.
  • One notable function that might be of interest for developers is eddystone_security_lock_code_init() since it determines how the lock code it generated.
    • Since the lock code is suppose to be an unique 16-byte value for any device, one way is to use the DEVICEID register of the FICR to get 8 bytes of unique value, then it's up to the developer to implement how the other 8 bytes are created.
    • For easier debugging and development purposes, there is currently an STATIC_LOCK_CODE definition which hard-codes the lock key to all 0xFFs.

• eddystone_flash

  • The flash module is an abstraction of the SDKs pstorage library and it organizes the flash blocks (32 byte each) nicely to fit the persistent data needs of Eddystone specifically. This module is used by eddystone_adv_slot to preserve and restore slot configurations between reboots, and used by eddystone_security to store the lock key and EID information. Check out the corresponding structures in the firmware to see how the data fields in each block are populated.

Flash blocks arrangement

• eddystone_advertising_manager

  • The advertising manager module manages the retrieval of advertising data from eddystone_adv_slotand adjusts the advertising intervals provided by the user to fit the capabilities of the hardware (esp. for eTLM encryption) before broadcasting the data. Read the comments inside intervals_calculate() to see the details of how advertising interval limits are handled and how you as a developer can tweak this to fit your needs.
  • Currently the advertising manager is set up to implement global advertising intervals only, but it can be adapted with some work to implement variable advertising interval by modifying how the timers behave in the module. The key function to note is fetch_adv_data_from_slot which gets the data from the eddystone_adv_slot module in the proper format and puts it into ble_advdata_set.

• eddystone_registration_ui

  • A simple app_button implementation that triggers a callback into eddystone_advertising_manager when BUTTON_1 is pressed in order to go into connectable mode advertising for registration and configuration of the beacon. This module can easily be modified to use another type of HW UI such as NFC, as long as a callback is made to eddystone_advertising_manager when the user action is detected.

• eddystone_tlm_manager

  • Module for computing the TLM frame in real-time whenever it is required by eddystone_advertising_manager. Currently it has no implementation of battery voltage sampling but it can be added by the developer by using the on-chip ADC and some wiring in the DK.

User Configs

Inside project\pca10040_s132\config you can find debug_config.h and eddystone_app_config.h which are useful for changing the debug and application behaviour respectively. Read the comments in those files for details.

Issues and support

This example application is provided as a firmware foundation for beacon providers or for users simply wanting to experiment with Eddystone. It is not part of the official nRF5 SDK and support is therefore limited. Expect limited follow-up of issues.

Third-party crypto libraries

The example application uses algorithms from the following third-party cryptographic libraries.

About

This application has been developed by the application team at Nordic Semiconductor as a demonstration of the Eddystone GATT Configuration Service. It has not necessarily been thoroughly tested, so there might be unknown issues. It is hence provided as-is, without any warranty. However, in the hope that it still may be useful also for others than the ones we initially wrote it for, we've chosen to distribute it here on GitHub. The application is built to be used with the official nRF5 SDK, that can be downloaded from http://developer.nordicsemi.com/.

Licenses

The nRF5 SDK for Eddystone licensing is split between the portion of the source code that originates from Nordic Semiconductor ASA and the portion that originates from third-parties.

• All source code, unless otherwise specified, originates from Nordic Semiconductor and is covered by the license present in documentation/license.txt in the nRF5 SDK:

• All source code contained under the following folder originates from third parties, and is covered by the corresponding licenses found in each of their respective subfolders:

  • crypto_libs

Note: The crypto_libs folder is not included in this repository but is created by running the setup script.