Wireless PDA Text Messaging

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

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Overview (contd)

• General Overall System
• Transmission
• Protocol

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Overview (contd)

• General Overall System (contd)
• Interfacing
• Palm OS

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Overview (contd)
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
(contd)
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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
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Software Packet Description (contd)
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

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Software Testing/Debugger (contd)

• POSE Palm OS Emulator

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Software Overall Flow Diagram
17
Software Overall Flow Diagram (contd)
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Hardware

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

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Hardware PDA
Sony Clie PEG-SJ Series
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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
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Hardware FM Receiver
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Hardware Antennas
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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