Critical Design Review

Critical Design Review Handmade by Robots

ECEN 4610 Spring 2006Hands-Free Low-Profile Wireless Radio

Team members

Derek Lindberg

Sean McDevitt

Nick Ciocco

Eric Hoffman

Chris Browne

Wireless Nothing

Critical Design Review



• Two-way wireless communication between two separate motorcyclists.

• Low-power, low-profile design for easy installation/integration inside helmet.

• Adjustable volume, microphone gain, and channel selection.

• Restricted access to broadcasted audio.

Project Overview



High Level Concept

Short range RF

Long range RF

Long range RF



Initial Set-backs – Wireless Transceiver

• nRF24Z1 – Only a point to point streaming device. • Not capable of handling TDD (time division

duplexing) or FDD (frequency division duplexing).

• nRF24L01 – Great device, but not yet in full production• Possible future use if breakout boards available

• nRF2401a – Current selection• Fastest data-rate for a “true” transceiver• Requires additional packet handling



Initial Set-backs - Codec

• TI TLV320AIC28 • I2C control format• QFN package

• TI TLV320AIC33• Not available (just released)• QFN package

• Xemics XE3006• Audio format is standard serial (not I2S)• Not available in quantities under 62

• TI TLV320AIC23B• Available with all needed features• SOP package

1

2 3

4



DAC CodecADC Codec

MicrocontrollerMicrophone Headphones

Transceiver

System Block Diagram - Headset

I2S I2SSPI



Block Diagram – Basestation

Microcontroller

Basestation to other

motorcyclisttransceiver

SPI Bus

Basestationto helmet

transceiver

• Serves as a booster for the helmet’s voice communications

• Handles channel allocation for slave headset



Transceiver(s)

Microcontroller

• 48kB Flash, 1024B RAM• Extremely-low power

• 330uA active• 1.1uA standby mode

• Dual 12bit DACs• SPI interface in hardware• 48 IO pins

• RS232 Interface via MAX3222 transceiver

• HANDLING SPI/I2S——SPI——

Audio Codec

Microcontroller – MSP430F1611



Timing Diagram I2S/SPI



Main System (Base Station) Schematic



Transceiver

• 2.4 GHz operating frequency• Low cost• Low power• 1Mbit/s ShockBurst Data Rate

• Low on-air time• SPI Communication• Dual-channel receiver (2Mbit/s)• Simple PCB antenna

——SPI——

Microcontroller

Receiving Transceiver

Transceiver – nRF2401a



Microphone

Microcontroller

Headphones

Audio Codec

• Convert between analog and I2S• Low power/Low cost• High quality 16 bit sound• DAC and ADC in single chip for simplicity• Integrated gain control, volume control and

speaker drivers if possible• SPI control from Microcontroller

——I2S——

——Analog——

Audio Codec – TLV320AIC23B



Current Project Plan – Divide and Conquer

• Printed circuit board tasks• Assemble• Test and debug• Begin second PCB revision

• Dev. board tasks• Establish communication between transceivers

• Experiment with data rate limitations using• Test maximum range and acceptable error rates.



MSP430F1611 Dev. Board with nRF2401a

• Prototype Base Station

• Provides test bed for extended functionality



Printed Circuit Board Rev. 1



Risks

• Difficulty making SPI communicate with I2S• High speed data rate and clock rate

• Unknown transmitter packet error rate at 1Mbps

• Difficulty with QFN package type (reflow)

• Wireless protocol complexity may be underestimated



Backup Plan

Use MSP430F1611 internal ADC/DAC SPI communication with I2S is removed

Use lower data rate for transceiver Voice still possible and known implementation at

this data rate exist Out-source transceiver assembly or use breakout

boards from SparkFun



Division of Labor

Group ResponsibilitiesDocumentation, system development, integration, system testing

Team Members Responsibility

Derek Lindberg Hardware layout and assembly, firmware programming

Sean McDevitt Antenna and Transceiver design

Nick Ciocco Transceiver design and PCB layout overview

Eric Hoffman Hardware layout and assembly, firmware programming

Chris Browne Assembly firmware programming, hardware integration



Project Timeline



Milestone 1 – March 23rd

• Printed circuit board assembled, tested, and debugged

• Microcontroller communicating with all peripherals

• Simple high-speed data transmission between two transceivers on development board

• Determine if addition of portable audio is feasible



Milestone 2 – April 20th

• Preliminary voice communication up and running• Microphone in and headphone out

• Base station to headset acquisition

• Preliminary protocol functionality

• Preliminary portable audio capability, pending Milestone 1



Budget/Final Parts List

Parts (per board) CostActive Components $60.00

Misc. Parts (all passive components) $5.00

Misc. Connectors $5.00

Total $70.00

Total (est. qty. 100) $30.00

Budget Breakdown Qty CostBase Stations 2 boards $140.00

Headset 8 boards $560.00

PCB 2 revs $300.00

Total -- $1,000.00



Questions ?



State Diagram – Headset

InitBase Station

Search Idle

Rx

Tx

Always

Pack

et T

x

Base Station Found

Wait Wait

Packet Decoded

Packet Received

Wak

e-O

n-V

oice



State Diagram – Base Station

InitHeadsetSearch Idle

Local Audio

RemoteTx/Rx

Voice T

imeoutV

oice

Det

ecte

d

Always

Voi

ce T

imeo

ut w

/o

Aud

io

Headset Found

Wait Wait

No A

udio PresentA

udio Device

Present

Aud

io D

evic

e Pr

esen

t

Headset Lost

Critical Design Review

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