1. Critical Design Review Handmade by Robots

2. Project Overview • 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. Handmade by Robots

3. High Level Concept Long range RF Short range RF Long range RF Handmade by Robots

4. 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 Handmade by Robots

5. Initial Set-backs - Codec 1 • 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 2 3 4 Handmade by Robots

6. System Block Diagram - Headset Microcontroller Microphone Headphones I2S I2S SPI ADC Codec DAC Codec Transceiver Handmade by Robots

7. Block Diagram – Basestation • Serves as a booster for the helmet’s voice communications • Handles channel allocation for slave headset Basestation to other motorcyclist transceiver Basestation to helmet transceiver SPI Bus Microcontroller Handmade by Robots

8. Microcontroller – MSP430F1611 • 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 Microcontroller ——SPI—— Transceiver(s) Audio Codec Handmade by Robots

9. Timing Diagram I2S/SPI Handmade by Robots

10. Main System (Base Station) Schematic Handmade by Robots

11. Transceiver – nRF2401a Receiving 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 Transceiver ——SPI—— Microcontroller Handmade by Robots

12. Audio Codec – TLV320AIC23B Microphone Headphones • 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 ——Analog—— Audio Codec ——I2S—— Microcontroller Handmade by Robots

13. 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. Handmade by Robots

14. MSP430F1611 Dev. Board with nRF2401a • Prototype Base Station • Provides test bed for extended functionality Handmade by Robots

15. Printed Circuit Board Rev. 1 Handmade by Robots

16. 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 Handmade by Robots

17. 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 Handmade by Robots

18. Division of Labor Group Responsibilities Documentation, system development, integration, system testing Handmade by Robots

19. Project Timeline Handmade by Robots

20. 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 Handmade by Robots

21. 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 Handmade by Robots

22. Budget/Final Parts List Handmade by Robots

23. Questions ? Handmade by Robots

24. State Diagram – Headset Tx Packet Tx Always Base Station Found Wake-On-Voice Init Base Station Search Idle Wait Packet Received Wait Packet Decoded Rx Handmade by Robots

25. State Diagram – Base Station Remote Tx/Rx Voice Timeout w/o Audio Always Headset Found Audio Device Present Init Headset Search Idle Voice Detected Voice Timeout Wait Wait Audio Device Present Headset Lost No Audio Present Local Audio Handmade by Robots