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

Outline  Objective  Overview  Software  Hardware  Difficulties  Questions

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.

Overview  Project Components 1. 2 PDA devices 2. 2 FM Transmitters and 2 FM Receivers 3. 4 RF antennas for over-the-air communication 4. Level Shifter for Interfacing RF ICs to the PDA 5. 2 power supplies for the transmitters and receivers

Overview (cont’d)  General Overall System  Transmission Protocol

Overview (cont’d)  General Overall System (cont’d)  Interfacing  Palm OS

Overview (cont’d)

Software  User Interface Description  Packet Description  Encryption/Decryption  Test Strategy/Debugger  Overall Flow Diagram

Software – User Interface Description

Software – User Interface Description (cont’d)

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

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

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

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

Software – Testing/Debugger (cont’d)  POSE: Palm OS Emulator

Software – Overall Flow Diagram

Software – Overall Flow Diagram (cont’d)

Hardware  Components 1. PDA 2. Level Shifter 3. Regulators for Power Step-Down 4. Power Supply (9V battery) 5. Transmitter/Receiver Pair (418mhz, 433mhz) 6. Antennas

Hardware – PDA Sony Clie PEG-SJ Series

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

Hardware – FM Transmitter

Hardware – FM Receiver

Hardware – Antennas

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

Questions