Hacker News Reader

Comment by flashman | Hacker News Reader

You can use a similar technique to clone a garage door remote control. You simply have to record the transmission using the techniques mentioned in this post, then rebroadcast it on the same frequency.

Broadcasting FM is as simple as loading a Raspberry Pi up with PiFM[0]. Or, if you don't have the original remote (but are a bit more technical), you can just brute force the combination; most remotes only use a 12-bit DIP switch (4096 combinations)[1].

[0] https://github.com/CodyJHeiser/PiStation [1] http://samy.pl/opensesame/

View on HN

Instead of a Pi you can use an Arduino with a RF module. The RF transmitter modulates at a standard frequency (e.g 433.92MHz), so the Arduino only has to send the code (a few bytes) at an appropriate frequency.

Here is an example I wrote, where I use this setup to turn on and off a remote controlled socket: https://github.com/andmarios/arduino/blob/master/lidlRemoteS...

Total cost could stay below $5 if you buy cheap components from eBay.

AFAIK some/most garage doors now use rolling-key encryption, like car keys.

Nice. I have a 30 year old garage opener but I don't have a remote. I know the combination because I set the DIP switches, and I think I even dug up the trasmission frequency when I looked into it a few months ago. I don't know what sort of transmission the opener wants to receive, though. Any resources you can point me to on that topic?

One thing I don't know how to do is encode information in pulses. That's why I use the record/replay method. There is probably a program that will convert a binary string to pulsed data (I believe 2ms chirps with 2ms gap between them?) but I don't know of it.

There is a little more information on the opening signal here: http://andrewmohawk.com/2012/09/06/hacking-fixed-key-remotes...

Unless I'm reading this wrong, GPIO4 is being used as a radio transmitter, but it can only do between 100.025Mhz and 99.975Mhz frequencies. Garage openers work mostly on 315 and, older ones, on 390 MHz.

I don't think the pi ships with a proper software defined radio.

The GPIOs generate (approximate) square waves with harmonics at 3 times the fundamental frequency, then 5 times, 7 times, etc. You can apparently use a filter to select only the third harmonic and transmit on 315 MHz that way.

Reply on news.ycombinator.com