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Wireless Null Modem

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Stephen Porter. Abstract ... for a DB-9 serial cable to transmit data to a ... Any IR Links unable to be implemented would be simulated by a null modem cable ... – PowerPoint PPT presentation

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Title: Wireless Null Modem


1
Wireless Null Modem
  • Infrared Palm Pilot Communication Device

2
Team Members
  • Team Leader
  • Peter Trenkle
  • Group Members
  • Huiyang Sim
  • Shaun McFarland
  • Stephen Porter

3
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
    PDA
  • Supply a cheap, convenient alternative to a
    laptop interfacing to an ASCII display menu

4
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
5
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

6
Design Constraints (Cont.)
  • Develop Software for PALM to Display ASCII Menus
    and Serial Data
  • Create a 1 meter Infrared Data Link
  • Power Entire Console with one 9V battery

7
Low Power Requirement
  • A new IR Xceiver allows for control of Duty Cycle
    and Current-Limiting Resistance
  • Duty Cycle and Current-Limiting Resistor can
    affect battery life
  • 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

8
Embedded Software Design
  • Used the PCs serial port to transmit serial data
    to verify the PICs onboard 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

9
Palm OS Software Design
  • Learned the CodeWarrior language for Palm OS
  • Started with Hello World program
  • Worked with Initial Serial Port programs
  • Program created that allows for bi-directional
    serial communication
  • Sends Data Bi-directionally from PC to Palm Pilot
  • User Input Functionality must be added
  • Changed serial port program to interface to the
    Palms onboard infrared port

10
Unforeseen Design Problems
  • Unconnected Ground Planes between Console and PC
    caused strange results
  • Intermittent Problems with CodeWarrior
    development system for PALM
  • Small Footprint of IR Xceiver is extremely
    difficult to interface to
  • Pin 4 (Receive) and Pin 8 (Gnd) are presently
    shorted together

11
Test Specification
  • Oscilloscope
  • Checked the clocking of the SPI Port of the PIC
    and the Data Rate of the RS-232 Interface
  • Allowed for complete verification of hardware
    design
  • Logic Analyzer
  • To test the actual movement of bits
  • Will allow for trigger on Chip Select to actually
    observe operation
  • Low Power Testing in a real-world environment

12
Low Power Testing
  • Power Testing and Verification takes 2 PHASES
  • Continuous Use (PIC constantly xmitting)
  • Typical Use (PIC periodically xmitting)
  • _at_ Different Baud Rates, Determine Time Until
    Battery Exhausted
  • Find Best Baud Rate Best Resistance
  • IR Xceiver can be put in SHDN mode between
    xmissions and still receive data
  • Following Formula will be used to determine power
    draw
  • Battery life in hours 120mAh / X ( mA drawn)

13
What We Promised
  • Demonstrate our bi-directional Palm Pilot
    terminal program
  • Any IR Links unable to be implemented would be
    simulated by a null modem cable
  • Transmit/Receive IR Data with limited IrDA
    functionality
  • PC Board would be laid out

14
Where We Are
  • IR Communication using Palm Pilot
  • Current Range Nearly 1 foot
  • Range Angle Maximum 30 degrees
  • Basic Serial Communication using PIC
  • Interfacing to UART thru SPI port
  • PC Board is laid out and ready for order

15
PCB Layout
16
Where We Stand
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
Serial Com Via Palm
Packetize Data
Infrared Com Via Palm
Final Testing and System Integration
17
Whats Left.
  • VT100 functionality for the Palm Pilot
  • Make I/O more efficient
  • Interrupt driven
  • Get rid of Polled Input
  • Address Power Concerns and nail down a battery
    life value when the product is robust
  • Second order of parts

18
Summary
  • IR console will soon be ready for packaging
  • Palm Pilot program that displays ASCII data on
    screen is working
  • Bi-Directional Communication is kind-of working
  • A convenient, low-cost alternative to null modem
    communications will soon exist!

19
Acknowledgements
  • We would like to thank Dr. Robert Reese, our
    advisor, for all his patience and input
  • We would also like to acknowledge Dr. Joseph
    Picone for his support

20
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.

21
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.
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