I have a question about a project, hopefully someone could have come across the same problem before me :
The goal is to replace the infrared communication of a remote with a radio communication with a XBee module (and a XBee receiver of course).
For that sake there is a quick and dirty solution that would consist into wiring some buttons of the remote directly into some XBee pins, but this is quite limited as you can guess.
The clever solution (I think) would be to plug the Xbee directly on a pin of the IR LED emitter… Depending of the button pressed, the IR LED emits a “pulsatile” signal, this pulsation is different depending on the pressed button… And you see my question coming now :
Would someone have a trick / or any idea / suggestion, to get this pulsation directly “parsed” into the XBee, so that the Xbee can guess what was the button pressed ? Or any other idea to sample somewhere on the remote chip a relevant info about the pressed button ?
Well that would not work if you connected to the XBee’s UART.
This might work into on of the XBee’s input pins and the XBee is setup to send the pin state on change. but the pin switching rate would need to be fairly slow. Check the XBee’s document on the fastest change of input it can detect and send.
Another big issue may be that the IR LED drive is modulated with a high frequency carrier (~38kHz is common). The XBee will not be able to respond to this. You need to know what the siganl to the IR LED is or look at it with an O’scope.
Now if you had an Asynchronous serial link the XBee can easily is used to make the link wireless.
Actually I can plug the led pin into a digital input, then the XBee transmits a series of data to the receiver… but this is not much readable
Another thought I have would be to read the IR LED output directly with a IR receiver… plugged to the emitter XBee : as far as I could read, the IR receiver could give a much more readable input depending on the blinking it sees. I ordered such a receiver, will do the tests as soon as received and keep it posted if I can get an interesting result !
Most IR is done by toggling the IR diode emitter at something like 38KHz. The serial data is on the order of 1Kbps and, essentially, serial data 1’s and 0’s gate the 38KHz carrier on and off. It’s a bit more than this, but it’s the gist.
On the receiving end (typical TV remote), a $3 IR receiver module has a chip which has a narrow bandwidth 38KHz filter to reject sunlight and lightbulb IR, a threshold detector, and a data out - this data being about the same as the 1Kbps at the transmitter.
Doing this with an XBee … to essentially make a wireless IR extender… isn’t straightforward. As you may know, there are lots of 434MHz and 900MHz wireless IR extenders. And extenders that use the existing TV coax to distribute IR signals to emitters, etc.
