Direct UART Serial to IR modulation

william chan

We all know that most IR remote controls use pulse width to send signals to the receiver.

Now, instead of using pulse width, I was thinking of using the serial 1s and 0s of a UART to directly modulate the 40Khz carrier to on and off.

Then the IR receiver will directly receive a serial signal as if the link is a serial cable, without any translations.

Would such a scheme be reliable?

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Mike Green

What do you mean by reliable? The scheme works and has been used before many times. It's subject to all sorts of interference from bright lights, etc. It's a half duplex link ... you can only send in one direction at a time. It does have the advantage of being very cheap and simple to implement.

PJAllen

It works for me.

http://forums.parallax.com/showthread.php?p=721739

LoopyByteloose

There are UARTs made to do just that. Usually they are part of an IRDA scheme that is relatively short distances [noparse][[/noparse]inches]·and high speed packets [noparse][[/noparse]>110K baud]·with CRC confirmation of their accuracy. These do take RS-232 at TTL levels and transmit with the modulation.· The advantage of using them is they also have a buffer.· But, it is possible to modulate the IR with a 555 timer calibrated to the appropriate frequency.

And, there really is no reason that one cannot use a slower BAUD and impliment a half-duplex serial interface.· The modulation is quite important as it keep the receiver from being confused by other source of IR flicker, like fluorescent lighting.

And, usually this scheme is more stable indoors than outside due to the intensity of background IR.· Shade and overcast weather conditions might help.· So, I generally think of IR remote control of any sort as primarily useful in a single interior environment.·

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