Here is a term project I did last month. The objective is simple. To transmit a IR message from PC to a receiver module few feet apart and show it on LCD. I created my own protocol for it, while another group used the RS232 protocol, just replacing the copper wire with IR beams.

The project mainly focuses on the development and implementation of a serial communication protocol. There are two parts for this purpose: the Software at the PC, and the firmware of the microcontroller, along with the circuitry. A text is entered at the PC end and a 32 character substring of the text is sent via infrared link to the microcontroller. The modulation technique employed is Pulse Duration Modulation for the data, and the character transmission rate for worst case is 18.18 / sec. The firmware supports to checking device ID. Each character sent must have the same device ID with the microcontroller in order to display it in the LCD.

Components Used:
Atmega32 Microcontroller 4MHz Crystal Shielded IR Receiver (3 pin)IRF840 MOSFET LCD Module (HD17238 Controller) 4081 And Gate 7805 Voltage RegulatorBC547 Transistor (2) 555 timer IC Resistors 10K, 1K, 100R Capacitors 0.01u, 4700uF, 4.7uFBreadboard & Breadboard wire


The text is first converted to a binary data stream. Each character is represented by 17 bits. Each Data frame sends the character, device ID and location of the character:







This data was output from the PC Parallel port. This signal was modulated at 38 kHz using On-Off-Keying (OOK). The IR receiver demodulates 38 kHz



Here a pulse duration modulation is used: A 4 sec high pulse means transmission start. A 2 ms high pulse means 1 A 1 ms high pulse means 0 A 4ms high pulse means the data-frame is starting to transmit The protocol is made from the scratch without any help from built in USART receivers of the microcontrollers. The protocol was implemented using the input capture feature of the microcontroller. A timer inside the microcontroller was configured to count up at 0.5MHz speed once in every 8 clock pulses.





























Circuit Diagram:

Transmitter:


Receiver:


Limitation
1.The PC side software was written with Visual Studio 2008. But the PC used did not meet the minimum requirements to run the software. As a result the PC side software was very slow, and thus the data transfer rate needed to be slowed down.
2. The PC software sends 32 characters regardless of the number of characters in the input stream. The remaining characters are filled up with white space characters. This might be overcome by keeping a command for clearing screen in the firmware of the microcontroller.
3. The PC software was configured to send 32 characters only. It could not send more than that at a time.
Pictures:






Full Files:

http://www.edaboard.com/viewtopic.php?p=1084270

http://www.avrfreaks.net/index.php?module=Freaks%20Academy&func=viewItem&item_id=1630&item_type=project
Here is a term project I did last month. The objective is simple. To transmit a IR message from PC to a receiver module few feet apart and show it on LCD. I created my own protocol for it, while another group used the RS232 protocol, just replacing the copper wire with IR beams.

The project mainly focuses on the development and implementation of a serial communication protocol. There are two parts for this purpose: the Software at the PC, and the firmware of the microcontroller, along with the circuitry. A text is entered at the PC end and a 32 character substring of the text is sent via infrared link to the microcontroller. The modulation technique employed is Pulse Duration Modulation for the data, and the character transmission rate for worst case is 18.18 / sec. The firmware supports to checking device ID. Each character sent must have the same device ID with the microcontroller in order to display it in the LCD.

Components Used:
Atmega32 Microcontroller 4MHz Crystal Shielded IR Receiver (3 pin)IRF840 MOSFET LCD Module (HD17238 Controller) 4081 And Gate 7805 Voltage RegulatorBC547 Transistor (2) 555 timer IC Resistors 10K, 1K, 100R Capacitors 0.01u, 4700uF, 4.7uFBreadboard & Breadboard wire



The text is first converted to a binary data stream. Each character is represented by 17 bits. Each Data frame sends the character, device ID and location of the character:





This data was output from the PC Parallel port. This signal was modulated at 38 kHz using On-Off-Keying (OOK). The IR receiver demodulates 38 kHz



Here a pulse duration modulation is used: A 4 sec high pulse means transmission start. A 2 ms high pulse means 1 A 1 ms high pulse means 0 A 4ms high pulse means the data-frame is starting to transmit The protocol is made from the scratch without any help from built in USART receivers of the microcontrollers. The protocol was implemented using the input capture feature of the microcontroller. A timer inside the microcontroller was configured to count up at 0.5MHz speed once in every 8 clock pulses.




























Circuit Diagram:

Transmitter:


Receiver:


Limitation
1.The PC side software was written with Visual Studio 2008. But the PC used did not meet the minimum requirements to run the software. As a result the PC side software was very slow, and thus the data transfer rate needed to be slowed down.
2. The PC software sends 32 characters regardless of the number of characters in the input stream. The remaining characters are filled up with white space characters. This might be overcome by keeping a command for clearing screen in the firmware of the microcontroller.
3. The PC software was configured to send 32 characters only. It could not send more than that at a time.
Pictures:






Full Files:

http://www.edaboard.com/viewtopic.php?p=1084270

http://www.avrfreaks.net/index.php?module=Freaks%20Academy&func=viewItem&item_id=1630&item_type=project