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Dids

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Posts posted by Dids

    Replicating a radio signal (433 MHz)

    in SDR - Software Defined Radio

    Posted

    You may want to check out some of the Yard Stick One Hak 5 episodes, what you are trying to do is almost exactly what it was designed for:

    https://revision3.com/hak5/how-to-hack-wireless-remotes-with-radio-replay-att

    You don't need to have that piece of hardware but those episodes could give you a good underlying basis for what you are trying to do and working with there.

    The maker of the ys1, Mke Ossmann, has some really good tutorials on his site as well going over the basics and working with they information here:

    https://revision3.com/hak5/how-to-hack-wireless-remotes-with-radio-replay-att

    Also any talk his given he usually goes into a ton of details.

    I can't remember if it's the ys1 or the hackRF (maybe both?) that there's basically a couple commands (record pattern/play pattern) where you don't even have to do all the decoding you just record it, then play it back.

    I should've watched the episode first. I'm guessing my data has padding, which is why there are no continuous 1's.

    Replicating a radio signal (433 MHz)

    in SDR - Software Defined Radio

    Posted

    Since my recordings don't have short and long pulses, I'm assuming I'm actually dealing with ASK modulation.

    There's a ton of things that are hard to figure out, including timing (mostly due to Audacity and microseconds).

    With this information, I'm fairly sure my preamble calculations are wrong, as I'm assuming I'll need to find a way to chop the recordings into equally sized bits (ie. length of one bit, or the bit rate), so I can clearly calculate the preamble length, silence length (or just instead X number of 0's there) and then figure out a way to send this data with more or less the same timing as with the recording.

    I'm not using a hackRF, as I'm creating a small embedded device with built-in wifi.

    Replicating a radio signal (433 MHz)

    in SDR - Software Defined Radio

    Posted

    Well that sure makes sense, now that I have something to compare it to! I hadn't realized how OOK actually worked, or even that it was in fact OOK, so I had no idea how to calculate the bits. It makes perfect sense now, and I can easily calculate all the signals by hand this way.

    Thanks Josef, you've been an absolutely huge help!

    I have pretty much those exact transmitters (got them from DealExtreme), so I should be good to go! Thanks again. :)

    Replicating a radio signal (433 MHz)

    in SDR - Software Defined Radio

    Posted

    I recently installed a very powerful LED based lighting solution to my office, but unfortunately it can only be controlled with a proprietary remote controller. As I've understood it, each remote and receiver are "paired" at the factory (no idea what kind of pairing technique they're using), and as far as I know they use one-way communication at 433 MHz (remote -> receiver).

    I've bought a SDR USB dongle which allowed me to accurately record the key presses, and it's relatively easy to see the signals. But since I'm very new to the world of SDR, I have no idea how to decode the signal, so I can replicate it on an Arduino or a Raspberry Pi, then use a 433 MHz transmitter (I have several transmitter boards) to send the replicated signal, to for example turn the lighting on or off.

    From all the guides and resources I've been researching, they all talk about OOK modulation, but my recorded data looks nothing like the ones I've seen online. I'm fairly sure it's not using OOK modulation, but then again, I know next to nothing about SDR or radio signals.

    Below is a link to a sample recording of a single recorded signal. I'm hoping that some of you who are more familiar with SDR could help me with this. Once I know how to decode or replicate one signal, I should be able to continue with the rest of them.

    Sample Recording (.wav): https://dl.dropboxusercontent.com/u/480/SDR_Sample.wav

    I've gathered the following information from these signals:
    - Bit rate is 40 nanoseconds
    - Preamble is 180 bits (90 highs and 90 lows)
    - Frequency is at around 433,895 MHz

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