Infra-Red Data Association (IRDA)

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Infrared Data Association (IRDA)

• E. Amir Ezzat Amir.ezzat_at_rashpetco.com

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Lecture topics

• What is Infrared light?
• Why IrDA?
• IrDA characteristics
• IrDA versions
• How IrDA works
• IrDA protocol Stack
• IrDA applications
• Adv. Dis-adv.
• Summary

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What is Infrared Light?

• Infrared radiation
  or "light is
  invisible
  
  electromagnetic
  radiation that
  
  has a longer
  wavelength than visible light and
  is detected most often by its heating effect.
• The name means "below red
• Red is the color of visible light of longest
  wavelength.

Infrared
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Infrared Band
Wavelength Spectrum
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Why IrDA?

• Infrared Data Association (IrDA) is the most
  common
• infrared connection today due to
• Standard (Different devices can
  communicate with each others)
• Low power consumption
• Low cost
• Simple (Easy to use)
• Higher security than RF
• Portable
• High noise immunity (No interference)

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IrDA characteristics

• The main characteristics of the IrDA technology
  are
• Family of standards for various speeds and
  purposes
• Up to 5m (75 kbps) and up to 1m (4 Mbps)
  communication
• Directional transmission with a cone covering 30º
  
• Data rates between 2.4 Kbps (control) and 16 Mbps
  (data)
• low power consumption with very-low power
  versions
• Works only in the direct "line of sight
• Signal may reflect from surfaces

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IrDA characteristics

• Can not penetrate solid objects
• Communicate using infrared LEDs photo diodes
• Communicate with minimal pre-configuration
• Provide point-to-point data transfer between only
  two devices at a time
• Devices include broad range of computing and
  communicating technology
• Inexpensive technology

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IrDA Versions

• Infrared technology used in local networks exists
  in four
• different versions
• IrDA-SIR (slow speed) infrared supporting data
  rates up to 115 Kbps
• IrDA-MIR (medium speed) infrared supporting data
  rates up to 1.15 Mbps
• IrDA-FIR (fast speed) infrared supporting data
  rates up to 4 Mbps
• IrDA-VFIR (very fast speed) infrared supporting
  data rates up to 16 Mbps

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How IrDA works

• Data is converted from electrical signal to
  infrared signal by using light emitting diodes
  (LEDs)
• Data is sent as an invisible light beam
• The beam is modulated (Switched on and off, to
  encode the data).
• The receiver uses a silicon photodiode to convert
  the infrared signal to an electric current.
• photodiode responds only to the rapidly pulsing
  signal created by the transmitter, and filters
  out slowly changing infrared signal from ambient
  light.

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How IrDA works

• Infrared communications are useful for indoor use
  in areas of high population density.
• IR does not penetrate walls and so does not
  interfere with other devices in adjoining rooms.
• Infrared is the most common way for remote
  controls to command appliances.
• Two IrDA devices can simultaneously send and
  receive mail, update calendar and contact
  information, and print documents
• A separate program controls each activity

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Infrared LEDs and Photodiodes
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Diodes in Device
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Design Factors Improve IrDA
Communication

• Design Factors Improve IrDA Communication
• Transparent window in front of IR module should
  be flat instead of curved
• Module should be recessed several millimeters
  into device case to minimize interference from
  ambient light

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IrDA Protocol Stack

• IrDA Protocol stack has
• several layers
• Physical Layer (IrPHY)
• Link Access (IrLAP)
• Link Management (IrLMP)
• Transport (Tiny TP)

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IrDA Physical Layer (IrPHY)

• Physical Layer IrPHY
• Controls hardware
• Function depends on which one of two standard
  is used
• Serial Infrared (Version 1.0)
• Fast Infrared (Version 1.1)

IrPHY
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Serial (Slow) Infrared

• SIR transmitter works like standard serial port
  on a PC
• Uses UART (Universal Asynchronous
  Receiver/Transmitter) chip on PC

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Parallel and Serial Transmission

• Parallel port transmits all eight bits as a byte
• Serial port transmits bits one after another

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Functions of the UART

• Converts bytes into a single serial bit stream
  for outgoing transmission
• Converts serial bit stream into parallel bytes
  for incoming transmission
• Can add an optional parity bit for error checking
• Adds and removes optional start and stop bits
• Provides some buffering of data to keep computer
  and the serial device coordinated
• May handle other interrupt and device management
  to coordinate speed of computer and device

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UART Frame
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Non-Return to Zero (NRZ)

• Standard RS-232 serial ports can use NRZ
  (non-return-to-zero) techniques that keep output
  level the same for the entire bit period

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Return-to-Zero Inverted (RZI)

• IrDA devices cannot use NRZ technology
• They use RZI that uses the inverse of RZ
• RZI increases voltage for 0 bit and no voltage
  for 1 bit
• UART has 16 clock cycles

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IrDA SIR Transmission
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Fast Infrared

• Specifies data transfer at 4 Mbps
• Retains backward compatibility with SIR devices

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FIR Transmitter Block Diagram
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FIR Transmission

• FIR uses 4 PPM
• Only two bits are transmitted
• Receiving device determines transmitted bit by
  locating pulse within time slot

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IrDA Link Access (IrLAP)

• IrDA Link Access Protocol (IrLAP)
• Encapsulates frames
• Defines how connections are established

IrLAP
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IrDA Link Management (IrLMP)

• IrDA Link Management
• Protocol (IrLMP)
• allows devices to detect other devices

IrLMP
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Transport Protocol (Tiny TP)

• IrDA Transport
• Protocol (Tiny TP)
• Manages channels
• Corrects errors
• Divides data into packets (At transmitter)
• Reassembles original data (At Receiver)

Tiny TP
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IrDA Applications

• PDAs
• Phones (Mobile)
• Printers
• Cameras
• Laptops
• Notebooks
• TV remote control
• Other Applications

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IrDA Advantages

• Standard (Different devices can communicate with
  each others)
• Low power consumption
• Low cost
• Simple (Easy to use)
• Higher security than RF
• Portable
• High noise immunity (No interference)

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IrDA Disadvantages

• Needs Line of sight
• Point to point connection only
• Blocked by solid materials
• Short range (5m)
• Light, weather sensitive
• Low Speed (Low Transfer data rate (4Mbps))
• Have to keep the device stable when transferring
  data
• Health dangerous (Can cause burns or blindness)

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Summary

• What is Infrared light?
• Why IrDA?
• IrDA characteristics
• IrDA versions (SIR, MIR, FIR and VFIR)
• How IrDA works
• IrDA protocol Stack (Physical, Link Access, Link
  Mngm and Transport)
• IrDA applications
• Adv. Dis-adv.

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Thanks

• E. Amir Ezzat Amir.ezzat_at_rashpetco.com