I'm probably quite far from being able to program the stuff, i'm asking this more out of curiosity (and perhaps also in hope someone that got the knowledge and skills might like the ideas)




The first one is, can the IR transceiver be used as a limited "radar", by emitting pulses and checking when they bounce back? To detect them bouncing back would need to detect what is the background IR radiation and then see when there is a spike above that in the intensity. Is the hardware and software fast enough for that? Or perhaps it could work just by constantly emitting IR and measuring the intensity of IR picked by the sensor, when it increases, if it's not just a quick spike, it might mean there is an obstacle getting closer (could get confused by incandescent lights, windows in a sunny day and devices talking with each other with IR though)

If it does work, it would be interesting to evaluate the possibility of using it as a virtual cane for blind people, and also for anyone walking in the dark.



The other idea is, would it be possible to use the FM transmiter and receiver to turn the N900 into a metal detector, or perhaps have it work like a sensor like on theremins?

Hi TiagoTiago,

afaik the IR module in the N900 only supports the sending of IR Signals, not receiving them (HW limitation).
You can use it as a remote for TVs for example, but not for communicating with other devices.
Using the camera to pick up the IR beam is also out of discussion, as it looks in the wrong direction (otherwise you could use it to detect how large/bright the IR-light "blob" is and measure the distance that way. But this would be really inaccurate).

Your second question goes in the same direction.
Metal detectors usually use a very distinct electromagnetic field. The direction is exactly known. N900s FM Transmitter emits also an electromagnetic field, but it will spread in multiple directions and measuring it with the FM receiver will yield to nothing.
Theremins work by measuring the field capacity. Your hand is like the second plate of a capacitor.

Sorry to disappoint you.

the IR transmitter is transmitter only like a TVremote (CIR) and even if the IR devices used in handhelds are not that powerful on the one hand and not that sensitive on the other.

So it isn't a transceiver like on many Nokia smartphones? Damn!


Regarding the metal detector/theremin idea, it's not possible to detect when there is some distortion in the signal, or some difference in how pulses fade/echo ?

No, as there is not much demand for IR any more, especially receivers, Nokia probably couldn't justify the cost of having a transceiver, but just added a transmitter because alone they are fairly cheap and can come in handy now and again.

That is disappointing, i was hoping eventually someone would make a prog that would record IR to learn how to communicate with undocumented devices :/

It still can be done. I'm using IR diode hooked into microphone port to record commands.

http://jumpjack.wordpress.com/2008/0...icator-just-1/

It may not be impossible.
It's in principle possible to record IR with the camera.
Place a remote _right_ up against the camera.
Trigger while watching viewfinder.
The stripy pattern contains data on the IR timing.

Is there a way to measure the resistance of the IR emitter of the N900 via software? Would it work if it was also emitting IR at the same time?

edit:I once read about this idea of using pulsing LEDs as touch sensors (one of the uses they suggested was for a toggle light switch), they would pulse and then stop emitting and the resistance would be monitored to see how long until the pulse bounces back, if it bounced quickly enough it would mean there is somthing very close to the LED

Transmitter was an all-in-one package, located in some chip they needed anyways (as far as I remember the design document I've read).