Mobile Robot Controlusing Bluetooth Low Energy

Bachelor Thesis – Till Riemer

Contents

Concept and Requirements

Project Background

Software Design

Realization

Conclusion and Outview

Concept

Real-world usage scenariosAgriculture/cleaning vehicles for limited space environments

Consumer Electronics

SWAT / Rescue operations

Camera control / Fly Cam

Archeology exploration

Concept

Requirements

Designed for Hardware available on stock for mass production

Extendability and portability

Peripheral totally remotely controllable

Control interface usable by non IT experts

Focus on power saving and speed in accordance

Background

BluetoothShort-distance wireless communication protocol

Currently version 4.0 (introduced LE)

Consists of several layers (profiles):- Physical (2,4Ghz band)- L2CAP- GAP (Piconet/Master/Slave)- ATT(GATT) (Client/Server)- HCI- …

Background

Bluetooth Low Energy

Extension to Bluetooth standard

Same frequency band and basic protocols

Reduced amount of adjusted profiles

Energy saving through shorter device discovery and sleep mode

Background

Parallax SumobotDevkit for robots participating in Sumobot contest

BASIC stamp controller, easily extendable

Atmel AVR ButterflyEmbedded board based on Atmega 169V MCU

U(S)ART interface (no HW flow control)

1x 16bit, 2x 8-bit HW timer with PWM support

-> power supply changed to Sumobot 4x1.5V

Background

Texas Instruments CC2540Embedded Development kit with BLE stack on single chip (8051 MCU)

Embedded/UART and USB version

Supporting single/dual CPU and Master/Slave mode

Closed-Source OSAL, BLE stack programmable on all layers

Background

Apple iPhone 4S

Software Design

System Architecture

Software Design

Butterfly application

Communication with CC2540 over HCIusing the UART interface

Receiving 1-byte movement commands over GATT, interpreting into predefined movement actions

example: Forward 1x -> GATT recv. 0x01 -> setMotorSpeed(50,50);

Servo control using hardware timer (PWM)

Software Design

Software Design

CC2540 application

Based on HostTestRelease sample project by Texas Instruments

Peripheral Mode

Registered functions handle external Bluetooth Messages and HCI commands

GAP on device, GATT transmission to host over HCI

Software Design

iPhone application

Based on TI example application

Model/View/Controller

Delegator

Buttons controling relative direction

3-step speed control

Realization

iPhone applicationMovements as predefined distinct values

Multi-tab viewusing Navigation Controllerand Swipe Gesture Recognizer objects

Movement buttons sending 1-Byte code over GATT

Several improvements such as status bar, differentConnection interval etc.

Realization

CC2540 application

Minor changes:

- UART flow control disabled

- GATT forwarding over HCI

- Peripheral device configuration

Realization

Butterfly application

Servos using PWM timer like in Sumobot project

UART:

- one-time Oscillator calibration

- Interrupt-driven UART driver + Message Queues

HCI interface

Conclusion

Current state

iPhone application more or less done, further improvements

Connection window to be optimized

GATT transmission over HCI tbd

Future testing

Conclusion

Possible Improvements

Control interface:- 3-axis gravity sensor control- Fluent 2D-space movement (-> Diablo)- Speech recognition (Siri?)

Authorization / AES encryption

XML data transmission protocol

Efficience analysis and power saving optimization

Thank you for attending!