about data communication via Infra Red..pls help me..

Hi everyone,
I need ur help to build a circuit for my sub-project.
I just want to transmit data using infra red (in range up to 20 cm), but i dont know how to make the circuit. I dont matter bout the carrier frequency.. (usually 38 kHz or the other). I still use microcontroller AT89S52. And I want to use TSOP 48xx (cz i havent try with photo-transistor or photo diode)

The problems are :
1. How can I modulate data with the carrier frequency? use AND gate or something else?
2. How can I demodulate? I think after TSOP or photo transistor receives data, it must be demodulated before it fed to the microcontroller. (Am I right?). Pls give me the demodulator circuit.
3. Should I use pin 3.0 (RxD) and 3.1 (TxD) in MCS-51 microcontroller to transmit and receive data?

I have found the similar project in this link : Simple infrared data communications
But I don't understand about PIC microcontroller.
I hope someone could give me the complete circuit (IR transmitter and IR receiver), using MCS-51 microcontroller (assembly). A.S.A.P.
Thx b4.

girl-next-door said:

Hi everyone,
I need ur help to build a circuit for my sub-project.
I just want to transmit data using infra red (in range up to 20 cm), but i dont know how to make the circuit. I dont matter bout the carrier frequency.. (usually 38 kHz or the other). I still use microcontroller AT89S52. And I want to use TSOP 48xx (cz i havent try with photo-transistor or photo diode)

The problems are :
1. How can I modulate data with the carrier frequency? use AND gate or something else?

Click to expand...

No need, just generate the 38KHz directly in the processor, simple software loops is all it needs.

2. How can I demodulate? I think after TSOP or photo transistor receives data, it must be demodulated before it fed to the microcontroller. (Am I right?). Pls give me the demodulator circuit.

Click to expand...

Nothing required, the TSOP demodulates and provides a 'similar' pulse train to the original input signal. Be aware though that it's NOT identical, and the width of the pulses will vary depending on many factors.

3. Should I use pin 3.0 (RxD) and 3.1 (TxD) in MCS-51 microcontroller to transmit and receive data?

Click to expand...

No, it's not a good idea, use a better protocol that doesn't require accurate timing.

Use TxD pin to modulate a carrier, yes an AND will work fine, to drive an IR LED. If you use a crystal that is a power of two of the carrier (within the 5% tolerance of the receiver) you can use a simple divider off of the crystal for your carrier, either on chip or off.

Use a **broken link removed** to drive the RxD pin.

Dan