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The house I moved into has these ceiling fan and  light combo units that are remote controlled. Since we’re setting up our own smart home system,   I want it to control these  fans and lights as well. So I’m going to figure out what  frequency the remote speaks on,   decode the messages, and then use a  Raspberry Pi to broadcast the same signals. Doing all of this doesn’t  require any expensive equipment. In fact, not counting the computer and Raspberry  Pi, the total cost of the gear is about $30. The key to understanding the signal that  the remote sends is this USB dongle.   It’s a USB TV tuner that was designed to let you  watch TV and listen to FM radio, but people found   out that the Realtek chip inside lets you receive  raw data from anywhere in its frequency range. And the frequency range is huge  - most of these Realtek TV tuners   can receive signals ranging from  double-digit megahertz up to 2 GHz, which would catch FM radio, TV,   amateur radio, automobile keyfobs,  cellphone signals, and tons more stuff. However, you can only tune  one frequency at a time, so   we’re going to use a piece of  free software called Spektrum. Spektrum lets us set a range, and it  continuously jumps through the range in a loop. I just need to plug in my TV tuner,  fire up Spektrum, and choose my device. The bigger the range, the slower  it takes to scan through it,   so I’m going to need to make an educated guess. It’s not going to be low enough  to be in the FM radio band, but   not high enough to share the cell phone bands. I know that garage doors and car  keys work on 300-400-ish MHz,   so this is probably also in that neighborhood. I’ll set a scan range of 200 to 600 MHz.   To make it easier to find, I’ll turn on the  max line which is like a high water mark. I should see a spike appear whenever  I push the buttons on the remote. OK, there it is. One big spike, and I’m going   to narrow down the range and  see what frequency it’s at. It’s looking like 304.2 MHz. Cool, so now I know what  frequency it’s speaking on. Next I need to decode it. I’m going to use a second program  called Universal Radio Hacker. This is a super convenient toolkit  for decoding binary data from RF. Here I’m choosing my receiver  and setting the frequency. What I’m going to do is record  just a couple seconds of signal,   and in the middle of the recording  I’m going to push the remote button. The shorter the recording,  the easier it is to handle. OK, I’ve got my recording, and you  can see that the signal in the middle   is much stronger than the noise before and after. In fact, the signal was clear  enough that Universal Radio   Hacker has automatically decoded the data  without me having to...