• Project Background

    With the release of iOS 7, Apple announced iBeacons, a feature that allows an iOS device to calculate its location relative to Bluetooth bea-cons. The MSU RCPD is looking to utilize this technology for assistive navigation by placing Bluetooth Low Energy beacons inside building en-trances and hallways. These beacons will allow iOS and Android based smart phones to calculate their position inside of building.


    Project Specification

    • Bluetooth Low Energy based beacon
    • Compatible with Apple's iBeacon protocol
    • Cost less than $20 per beacon
    • Resistant to tampering and reprogramming
    • Powered by AC outlets
    • Applications for iOS and Android devices
  • iBeacon Interacts with iDevices

  • Design Phases

  • Phase one: Bluegiga based design

    This design uses a Bluegiga BLE112 mod-ule designed to make implementing Bluetooth functionality straightforward. The BLE112 has a built in antenna and is based on the TI cc2540 SoC BLE chip. The BLE112 requires fewer number of external components, but the cost is higher.

    Bluegiga BLE Module Interacting with iPhone and an Android Phone
  • Phase two: TI based design

    This design uses a TI cc2540 BLE chip to im-plement the Bluetooth functionality. The TI cc2540 is a system on a chip (SoC), meaning no external microcontroller will be needed. The cc2540 chip does need an external antenna to operate.

    TI cc2540 Development Board

  • Final Design and Demonstration

  • Final Design

  • Final Design Layout

  • Based on the design requirements and the rankings of the possible designs, the TI cc2540 based design was selected. Initially a prototype beacon was built using the Bluegiga BLE module because it includes all the necessary components to begin software development. This allowed the group to become familiar with the BLE and the iBeacon protocol while concurrently developing the more complex hardware of the TI design.

    The final beacon design focused on creating a low cost solution, with minimum impact to the performance. A custom PCB was created to implement the support circuitry required by the cc2540. Cost saving measures such as using a PCB antenna instead of a discrete IC based antenna and a 2layer PCB instead of the 4layer PCB common in RF designs. The simple operation of the BLE beacon helped keep the component cost low.

    • Software Demonstration

    • Bluetooth Packet Breakdown
      • Preamble: Either 10101010 or 01010101
      • Access Address: Fixd for advertising packets
      • Protocal Data Unit (PDU):
        • iBeacon prefix: Fixed value
        • UUID/Major/Minor bits: Used to identify individual beacons
        • Tx Power: Used to calculate distance to beacons
      • CRC: Cyclic Redundancy Check

      • Picture above shows our Android and iOS softwares interacting with our beacon, displaying the UUID/Major/Minor bits and distances.

      Picture on the left shows our beacon interacting with Android phone with Radius Network application.

      Budget

    • Projected Budget
    • Final Budget

    • In total, after developing two prototypes and the final design, the final cost of the project was $272.78. The proposed cost of the project was $330, therefore the project was completed $60 under budget. The actual cost of the final design is $16.45. It fits in the price range given by the sponsor RCPD and If the beacons were used on a large scale throughout campus the price per unit of the beacon would go down due to the discounted prices of components ordered in bulk. The price per unit for constructing 500 beacons would be $9.92, which meets the design objective better.

    • Project Summary and Future Improvements

    • Overall, the project is a success since all of the design specifications were achieved. The cost per beacon is well under $20 and the beacon allows for reusability of the code and design by the RCPD for future developments. The beacon performs well enough for it designed purposes however the accuracy of the distance from beacon to receiver was not as stable as expected.

      Even with success, there are still areas of improvement that can be made on the beacon. Improvements can be done on the PCB layout for the components.There are four layouts for capacitors that need to be added on the PCB layout to allow the beacon to properly function. In addition, the polarity layout for the DC jack needs to be reversed. The team was able to fix these layout errors by soldering components over the PCB but future revisions should fix the errors on the actual PCB layouts. For future iterations, the beacon can be design to be battery powered.

      In regards to software, a database needs to be implemented in order to match the UUID, major byte and minor byte to a name for a precise location. More accurate averaging algorithm is needed for the Android side to further increase the distance measured from the beacons and triangulation could be added to improve it even more. On the firmware side, it may be possible to update the firmware remotely and prevent tampering at the same time using OAD method, but it requires more work on the encryption of the firmware on both ends.

    • Final Design Circuit