Wireless Null Modem

1
Wireless Null Modem

• Infrared Palm Pilot Communication Device

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Team Members

• Team Leader
• Peter Trenkle
• Group Members
• Huiyang Sim
• Shaun McFarland
• Stephen Porter

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Abstract

• Design an infrared console that eliminates the
  need for a DB-9 serial cable to transmit data to
  a PDA
• Develop software that will allow users to
  establish a data link between the console and the
  Palm Pilot

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Motivation

• Palm Pilots are cheaper and easier to carry than
  laptops with null modem cables
• Infrared technology has allowed for low-speed
  data links in handheld computing devices
• Ability to supply a cheap, convenient alternative
  to a laptop interfacing to an ASCII display menu

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Why Use Infrared Technology?

• Infrared technology is perfect to replace the
  cable required by the RS-232 interface
• Low level infrared data links can transmit data
  at up to 115.2 kbps
• Infrared data links are feasible at distances of
  up to three meters
• Infrared standard will allow for thousands of
  products to interface to our design

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Design Constraints

• Design an Infrared Console to Establish a Data
  Link and Tx/Rx RS-232 data through the Infrared
  Data Link
• Transmit and Receive Infrared Data at a Rate of
  19.2kbps with a Bit Error Rate of 10E-9
• Develop Software for PALM to Detect a Data Link
  and Display ASCII Menus

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Design Constraints

• Create a 1 meter Infrared Data Link
• Physical Packaging
• The size will be no larger than 2 x 1.5 x 2.25
  (H x W x D)
• Components have small footprints
• Cost
• The cost of parts and packaging will be lt 30

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Low Power Requirement

• Typical use of our product will be defined as 15
  minute intervals, with long delays between use
• One 9 Volt battery will be used to supply power
  to our project
• Due to the excessive power needed by the IR
  transceiver, several aspects of the transmitted
  data are observed
• screen refresh rates
• amount of characters on each screen
• By knowing the current rating of the 9V battery
  (120mah _at_ 9V) we can define a simple formula
  showing battery life depending on current drawn

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Low Power (cont.)

• Battery life in hours 120mAh / X ( mA drawn)
• The PIC, External UART, and Line Driver pull
  approximately 2mA at the given clock speed (4Mhz)
• The IR Transceiver draws several times more power
  (100mA) depending on the length of time it
  transmits
• This will be limited by controlling the duty
  cycle and transmission rate of the IR Transceiver
• Maximum Power will be determined when final
  prototype is developed

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Development Plan
Hardware Design
Determination of Components
Finished Schematic
Palm OS Dev.
PIC C Firmware Dev.
Hello World On Palm
Basic Serial I/O into the PIC
Packetize Data
Serial Com Via Palm
Implement IrComm Standard
Infrared Com Via Palm
Final Testing and System Integration
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Hardware Design

• Hardware was chosen by considering the Design
  Constraints
• Power Consumption
• Performance at low clock speeds, further decrease
  power consumption
• IrDA Timing Compatibility
• Large amounts of buffer space for creating
  packets of data

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Diagram of Hardware
PIC Controls capture of serial data from SPI Port
and UART. This data is then decoded from/encoded
into IrDA compatible data
From RS-232 _at_ 19.2 kbps
MAX3100
To PALM
Maxim 3100 Controls IrDA Timing for the PIC
Infrared Transceiver
From PALM
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Component Costs
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Embedded Software Design

• Use the PCs serial port to transmit serial data
  to verify the UART
• Create Modular I/O routines for SPI module on PIC
• Interface the PIC to the Max3100 UART to control
  IrDA timing
• Transmit and Receive Data between the RS-232
  Interface and the Infrared Interface
• Port existing IrComm Assembly Code into C Code
• Build the IrDA protocol layer by layer, testing
  each as it is completed
• Test the final software program using IrPing()

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Palm OS Development

• Learn the basics of the CodeWarrior language for
  Palm OS
• Work on Hello World program
• Start with Initial Serial Port programs
• Create a program that allows for bi-directional
  serial communication
• Send Data Bi-directionally from PC to Palm Pilot
• Add User Input Functionality
• Move serial port program to interface to the
  Palms onboard infrared port

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Test Specification

• IrPing() IrDA protocol stack analyzer for the
  Palm
• Will test the IR data sent by the Console and
  Palm
• Will verify the IrDA protocol layers implemented
  in Firmware
• Oscilloscope
• Will check the clocking of the SPI Port of the
  PIC and the Data Rate of the RS-232 Interface
• Will allow complete verification of hardware
  design
• Performance Testing
• Create a real world simulation environment
• Perform Peak Performance Testing and Typical Use
  Testing
• PCs IR port will act as Bit Error Rate Tester

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Test Specification
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End of Semester Delivery

• Demonstrate our bi-directional Palm Pilot
  terminal program
• Any IR Links unable to be implemented will be
  simulated by a null modem cable
• Transmit/Receive IR Data with limited IrDA
  functionality
• Complete IrDA functionality will be completed by
  February of 2002
• PC Board will be laid out and ready for order

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Summary

• Design and Implement a small, low-power RS-232 IR
  console
• Create a Palm Pilot Program that displays ASCII
  data on screen
• Create a convenient, low-cost alternative to
  laptop-to-serial-cable communications

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Future Applications

• Remote control of Serial Devices
• Make software compatible with different PDAs for
  greater market penetration
• TCP/IP functionality to allow for low speed
  internet connections on the PDA

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Acknowledgements

• We would like to thank Dr. Robert Reese, our
  advisor, for all his valuable input
• We would also like to acknowledge Dr. Joseph
  Picone for his support

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References

• 1 "About IrDA Software Protocol,
  http//www.irda.org/standards/standards.asp,
• Infrared Data Association, Walnut Creek,
  California, 1996.
• 2 P. Barker and A. C. Boucouvalas, Effect of
  Random Alignment Sway on the
• Performance of IrDA Handheld Devices,
• http//www.irda.org/design/reference.asp,
  Infrared Data Association, Walnut
• Creek, California, 1996.
• 3 M. Cremer, An Introduction to the IrDA
  Protocols, PDA Developers 2.6,
• pp. 35-39, Nov/Dec, 1994.
• 4 T. Engdahl, "Get Power Out of PC RS-232
  port,
• http//www.epanorama.net/circuits/rspower.html,
  Epanorama.net Electronic
• Circuit Design, August 25, 2001.
• 5 L. Goldberg, Infrared Data Transmission The
  Missing Link? Electronic
• Design, pp. 47-64, April 17, 1995.

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References

• 6 "IrCOMM Serial and Parallel Port Emulation
  over IR (Wire Replacement),
• http//www.irda.org/standards/standards.asp,
  Infrared Data Association, Walnut
• Creek, California, 1995.
• 7 "IrDA Data Link Design Guide,"
  http//www.hp.com/go/ir, Hewlett Packard, Palo
• Alto, California, 2000.
• 8 C. Knutson, Infrared Data Communications
  with IrDA, presented at IrDA
• Conference, 1998.
• 9 P. Langley, Leading Alternative for Serial
  Ports IRDA, Electronic
• Engineering Times, p. 54, August 17, 1998.
• 10 P. Megowan, IrDA Infrared Communications
  An Overview,
• http//www.irda.org/design/reference.asp,
  Infrared Data Association, Walnut
• Creek, California, 1996.
• 11 T. Salazar, UART test mode provides clock
  for RS-232-to-IrDA translator,
• Electronic Design, pp. 124-125, February 21,
  2000.
• 12 "Serial Infrared Link Access Protocol
  (IrLAP) Version 1.1,
• http//www.irda.org/standards/standards.asp,
  Infrared Data Association, Walnut
• Creek, California, 1996.