![]() The body part contains 16 bits of instruction in binary format, each corresponding to a button on the remote control. After this, eight bit 0 are sent, followed by eight bit 1s. The header part starts with a 9.2 ms of high signal, followed by 4.4 ms of low signal. A bit 1 is represented by 600s high pulse followed by 1.6ms low pulse. A bit 0 is represented by 600s high pulse followed by 500s low pulse. Any signal sent by the remote control contains three main parts: header, body, and trigger. To find out the protocol of the signal, we connect an oscilloscope to the output of the IR photodetector and analyze the signal for a button press of the remote control. Most use a byte based code that is modulated on top of a 30-40Khz carrier wave. There are several standards for Infrared remote communications. Because we wanted the device to continue functioning when power was removed, we chose to us an RTC (DS1305) with a backup battery. Also, we had to choose whther to keep track of times on the AtMega, or whether to use an external clock. Since the CTC timer on the AtMega allowed us to generate approximately the correct waveform without any additional hardware we chose to use it. One of the tradeoffs was whether to handle modulating the IR LED using the AtMega, or a separate frequency generator. uControl periodically checks EEPROM for events to be run, and make add or remove events by the users request. The EEPROM is used to store scheduled events. The IR LED Output is used to control the DVD Player by sending the same signal that the remote control of the DVD Player would send. The hyperterminal output is mainly used for feedback to the user after they have entered a command. However, since this method can be tedious, an alternative way would be to use the remote control to enter the actions. One way to do this is by entering commands corresponding to each action. When the user creates a new scheduled event, they must specify the actions to be taken. The remote control input is used only when recording a scheduled event. By entering Unix like commands, the user can control the DVD player, edit the event scheduling, as well as edit the setting of the device. The hyperterminal input is the main way for user to interact with the device. Finally, we implemented the real time clock. Once we got the EEPROM to receive and transmit data, and the IR Photo Detector to read IR signal from the remote control, we implemented the infrared LED. The IR Photo Detector was used for detecting the type of signal emitted by the DVD Player remote control, so that we can learn the bit pattern for each button press and the format of the infrared signal. The EEPROM was used for storing scheduled events. We started by implementing the most crucial elements of uControl: the EEPROM and the IR Photo Detector. The project was completed in several stages. So, we chose to test the device on a DVD Player. Testing this on a television alone definitely limits the range of actions that we can demonstrate. However, due to time constraint, we can only afford to test this device on one electrical device. The user can program the series of actions to be executed by the television at a time that they also specify. Therefore, we decided to create a device, uControl, that can automatically turn on a television at a scheduled time, switch to the correct channel, and start recording at a desired time. While recording the shows does get around this problem, keeping track of it is very troublesome. High Level Design RationaleĪs Cornell Engineering students, we are so busy with homeworks and projects that we tend to miss a lot of television shows. When the time arrives, the device will automatically execute this sequence of button pushes. These are done after setting the execution time of the button push sequence. To schedule the sequence of button pushes, the user can use the computer to program the device, or use their remote control to have the device record the sequence of button pushes. However, unlike remote controls, uControl allows the user to program a sequence of button pushes that will automatically run at a time that they can set. ![]() The uControl allows the user to control their DVD player as if they are using a remote control. ![]() This project creates a programmable device that can control a DVD player on scheduled times by sending infrared signals.
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