IR Control

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IR Control

• Materials taken from a variety of sources
  including IR Remote for the Boe-Bot
• by Andy Lindsay

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The Plan Use a TV Remote to Communicate with the
Arduino
IR signal
Sony TV remote control
PWM
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What is IR Visible Light Waves
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What is Infrared
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The IR Signal

• The IR detector is only looking for infrared
  thats flashing on and off 38,500 times per
  second.
• It has built-in optical filters that allow very
  little light except the 980 nm infrared.
• It also has an electronic filter that only allows
  signals around 38.5 kHz to pass through.
• This is the type of signal produced by the remote
  control.
• This prevents IR interference from common sources
  such as sunlight and indoor lighting.

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Important Concepts

• Pulse width modulation (PWM) Pulse durations are
  used in many applications, a few of which are
  motor control, and communication. Since the IR
  detector sends low pulses that can be measured to
  determine what information the IR remote is
  sending, it's an example of using PWM for
  communication.
• Carrier signal The IR remote uses a 38.5 kHz
  "carrier signal" to transmit the pulse durations
  from the remote to the IR detector.
• Communication protocol A communication protocol
  is a set of rules for devices that have to
  exchange electronic messages. Protocols tend to
  have rules for voltages, the amount of time
  signals last, carrier signal frequencies and/or
  wavelengths, and much more. When two or more
  devices follow the rules of a given protocol,
  they should be able to communicate and exchange
  information.

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The TV Remote Control (4 Function Universal
Remote)

• You must configure your universal remote so that
  it sends PWM messages to a television set using
  the SONY protocol.
• TV remote setup
• Press and release the TV key.
• Press and hold the SET key until the indicator
  LED on the remote turns on and stays on.
• Use the digit keys to enter 0001. The LED may
  turn off briefly as you press each digit.
• VCR remote setup
• Press and release the VCR key.
• Press and hold the SET key until the indicator
  LED on the remote turns on and stays on.
• Use the digit keys to enter 1028. The LED may
  turn off briefly as you press each digit.

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The TV Remote Control (SYSTEMLINK 3 RCA)

• You must configure your universal remote so that
  it sends PWM messages using the SONY protocol.
• TV remote setup
• Press and hold the CODE SEARCH button until the
  indicator LED lights, then release the CODE
  SEARCH button.
• Press and release the TV button (the indicator
  LED will blink and then remain lit).
• Use the digit keys to enter the code 002. After
  your code is entered, the indicator LED will turn
  off.
• VCR remote setup
• Press and hold the CODE SEARCH button until the
  indicator LED lights, then release the CODE
  SEARCH button.
• Press and release the VCR button (the indicator
  LED will blink and then remain lit).
• Use the digit keys to enter the code 004. After
  your code is entered, the indicator LED will turn
  off.

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The Sony Protocol
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Protocol Details

• This message consists of thirteen negative pulses
  that the Arduino can easily measure.
• 1 the start pulse, which lasts for 2.4 ms.
• 2-13 will either last for 1.2 ms (binary-1) or
  0.6 ms (binary-0).
• 2-8 indicates which key is pressed.
• 9-13 indicate if the message is being sent to a
  TV, VCR, CD, DVD player, etc.
• Pulses are transmitted in least significant bit
  first fashion.
• the first data pulse is bit-0.
• the next data pulse is bit-1
• Etc.
• If you press and hold a key on the remote, the
  same message will be sent over and over again
  with a 20 to 30 ms rest between messages.

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How the IR Detector Works

• Our IR receiver is the same detector found in
  many TVs and VCRs.
• This detector sends a low signal whenever it
  detects IR flashing on/off at 38.5 kHz and a high
  signal the rest of the time.
• When the IR detector sends low signals, the
  processor inside a TV or VCR measures how long
  each of the low signals lasts. Then, it uses
  these measurements to figure out which key was
  pressed on the remote.
• Like the processor inside a TV, the Arduino can
  be programmed to detect, measure, store, and
  interpret the sequence of low pulses it receives
  from the IR detector.

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Schematic for IR Detector
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pulseIn Command

• The syntax for the pulseIn command is
• pulseIn (Pin, State)
• Pin the I/O pin for measuring the pulse.
• State is used to determine whether the pulse is a
  HIGH or LOW
• Option third input max duration in millisecs
• The output of the IR detector is inverted (i.e.,
  LOW).
• pulseIn(pin, LOW)
• pin is the pin connected to the IR detector

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Using pulseIn()

• while(pulseIn(9, LOW) lt 2200) //Wait for
  start bit

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Interpreting the IR Message

• The Idea represent the pulse sequence as a bit
  sequence.
• The IR message consists of thirteen pulses with
  the following format
• 1 the start pulse lasts for 2.4 ms.
• 2-13 will either last for 1.2 ms (binary-1) or
  0.6 ms (binary-0).
• Map the duration of pulses 2-8 to their
  corresponding binary value
• Use pulseIn() to measure pulse length
• Use the bitSet() to create the corresponding
  binary representation

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Program for Reading IR Signals

• ReadIR
• Programming Features
• pulseIn() and bitSet()
• Arrays
• A debug flag to turn on printout
• Throws away devise designation
• Adjusts bit pattern to match numeric keys

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Program for Controlling Bot

• IRcontrol
• Programming Features
• Switch statement
• Servo library