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Step 2Infrared modulation
Now, this is the theory, if you don't want to know how to reverse-engineer an IR remote control, you can just skip to step 6.
Ok, so the helicopter isn't controlled with a 'normal' radio remote, but is controlled with a cheaper Infrared remote.
This is just great because we can more easely reverse-engineer the thing ! We only need a component called an IR detector or IR demodulator.
Now this page has an excellent tutorial on how infrared modulation works, but I'm only going to resume it quickly here :
As you know, the sun, as well as most heat sources, including light bulbs, emits infrared radiation. Infrared modulation is a technique that involves PWM-ing an Infrared led at a certain frequency (here 38kHz) to 'bypass' the IR radiation from ambient light : the IR demodulator only accepts 38kHz modulation, filters out everything else, and gives a clean logic (0 or 1) output. It gives a logic LOW (0volts) output when it detects a modulated IR signal.
There's a device like this on all TVs/DVRs/DVD players, etc.. Fortunately, this thing doesn't cost much , is really easy to interface with a microcontroller/logic analyzer and will allow us to reverse-engineer the IR protocol used by our helicopter remote without opening the remote !
BTW, the image below kinda illustrates well how IR modulation works : the remote gives the signal on the left, the demodulator gives the one on the right.
Now let's move on to step three : preparing our improvised 'logic analyzer' .
Ok, so the helicopter isn't controlled with a 'normal' radio remote, but is controlled with a cheaper Infrared remote.
This is just great because we can more easely reverse-engineer the thing ! We only need a component called an IR detector or IR demodulator.
Now this page has an excellent tutorial on how infrared modulation works, but I'm only going to resume it quickly here :
As you know, the sun, as well as most heat sources, including light bulbs, emits infrared radiation. Infrared modulation is a technique that involves PWM-ing an Infrared led at a certain frequency (here 38kHz) to 'bypass' the IR radiation from ambient light : the IR demodulator only accepts 38kHz modulation, filters out everything else, and gives a clean logic (0 or 1) output. It gives a logic LOW (0volts) output when it detects a modulated IR signal.
There's a device like this on all TVs/DVRs/DVD players, etc.. Fortunately, this thing doesn't cost much , is really easy to interface with a microcontroller/logic analyzer and will allow us to reverse-engineer the IR protocol used by our helicopter remote without opening the remote !
BTW, the image below kinda illustrates well how IR modulation works : the remote gives the signal on the left, the demodulator gives the one on the right.
Now let's move on to step three : preparing our improvised 'logic analyzer' .
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