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

The Plan: Use a TV Remote to Communicate with the Arduino IR signal Sony TV remote control PWM

What is IR: Visible Light Waves

What is Infrared

The IR Signal The IR detector is only looking for infrared that’s 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.

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.

The BRIGHTSTAR TV Remote Control You must configure your BRIGHTSTAR universal remote so that it sends PWM messages using the SONY protocol. Press and hold the SET-UP button until the indicator LED blinks and remains on, then release the button. Use the digit keys to enter the code 605. After your code is entered, the indicator LED will turn off and you are done.

The Sony Protocol

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.

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.

Schematic for IR Detector

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

Using pulseIn() while(pulseIn(9, LOW) < 2200) { } //Wait for start pulse

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

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

Program for Controlling Bot IRcontrol Programming Features: Switch statement Servo library

Adding a Speaker Any digital pin will work