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Wireless PDA Text Messaging

Wireless PDA Text Messaging. A Full-Duplex Messaging System between 2 PDAs Jency Jacob Talat Ozyagcilar. Outline. Objective Overview Software Hardware Difficulties Questions. Objective.

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Wireless PDA Text Messaging

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  1. Wireless PDA Text Messaging A Full-Duplex Messaging System between 2 PDAs Jency Jacob Talat Ozyagcilar

  2. Outline • Objective • Overview • Software • Hardware • Difficulties • Questions

  3. Objective • The objective is to equip 2 PDA devices in a way such that users are able to simultaneously send and receive messages between one PDA and another.

  4. Overview • Project Components • 2 PDA devices • 2 FM Transmitters and 2 FM Receivers • 4 RF antennas for over-the-air communication • Level Shifter for Interfacing RF ICs to the PDA • 2 power supplies for the transmitters and receivers

  5. Overview (cont’d) • General Overall System • Transmission Protocol

  6. Overview (cont’d) • General Overall System (cont’d) • Interfacing • Palm OS

  7. Overview (cont’d)

  8. Software • User Interface Description • Packet Description • Encryption/Decryption • Test Strategy/Debugger • Overall Flow Diagram

  9. Software – User Interface Description

  10. Software – User Interface Description(cont’d)

  11. Software – Packet Description Header - $FF End of Data - $01 (more data), $00 (done) Encoding Sequence # -Range 0 - 255 End of Packet- $9F Packet Sequence # - Range 0 to 6 1st Data - 4 bytes of encoded user message Checksum - Packet Mid-point 2nd Data - 6 bytes of encoded user message

  12. Software – Packet Description (cont’d) Header- $F5 Control Indicator -$F1FA(Connection Establishment) , Packet Seq # (ACK) End of Packet - $9F

  13. Software – Encryption/Decryption • Encoding sequence number • Encryption table: Identical static tables containing random numbers • Encoding: Encoded data = Data + Encoding # • Decoding: Decoded data = Data – Encoding #

  14. Software – Testing/Debugger • Debugger Module • Viewing receive buffer and various error flags • Sending/Receiving single packets

  15. Software – Testing/Debugger (cont’d) • POSE: Palm OS Emulator

  16. Software – Overall Flow Diagram

  17. Software – Overall Flow Diagram (cont’d)

  18. Hardware • Components • PDA • Level Shifter • Regulators for Power Step-Down • Power Supply (9V battery) • Transmitter/Receiver Pair (418mhz, 433mhz) • Antennas

  19. Hardware – PDA Sony Clie PEG-SJ Series

  20. Hardware – Level Shifter/Regulators/Power Supply • Level Shifter – TTL to CMOS Level Converter • Regulator – Obtaining 3.3V & 5V from 9V Battery • Power Supply – 9V Alkaline Battery

  21. Hardware – FM Transmitter

  22. Hardware – FM Receiver

  23. Hardware – Antennas

  24. Difficulties • Capturing data in dedicated receive buffer • Utilizing the processor between handling events and capturing/processing packets • Handling noise introduced to the system through the transmitter/receiver pair

  25. Questions

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