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Full duplex is such a big deal. As an example, I have some remote controlled ceiling fans in my house. They're controlled by dumb RF remotes, but I wanted to
by fpgaminer 9y ago
Full duplex is such a big deal.
As an example, I have some remote controlled ceiling fans in my house. They're controlled by dumb RF remotes, but I wanted to make them smart so they can be controlled from Alexa.
Being a total SDR novice I figured it'd be easy to use an SDR to tackle this. But after much searching, I discovered full-duplex SDR is _super_ expensive. I think HackRF is the cheapest one at ~$500?
So instead I grabbed an RTL-SDR dongle and some dumb, cheap RF transmitters (the fixed frequency kind that you just dump a digital signal into) that had roughly the same frequency as the fan's remotes.
It only took me a day to get the RTL-SDR working, capture some of the remote's signals, and decode them. But when I tried to recreate the signals using the RF transmitter I grabbed they only worked 10% of the time. Maybe my timing was off. Maybe my antenna was cruddy. Maybe the frequency of the RF transmitter was too far off from the remote's. I felt intimidated by the big, scary black magic of RF. So I gave up.
I ended up just cracking open one of the remotes and soldering relays to all the button pads. An ESP8266 later and I can control all the fans in the house using Alexa. Not bad for a day's work.
But it would have been a lot nicer and cleaner to just use a full duplex SDR. Awesome to see something affordable finally coming out!
- wyldfire 9y agoWhy not use multiple RTL-SDRs?
- ac29 9y agoRTL-SDR cant transmit.
- ac29 9y agoDoubt you would need full duplex there. I can't imagine that the fan had a transmitter or that the remote had a receiver. Even if they did, I would be really surprised if they were both full duplex radios.
- baobrien 9y agoHackRF is closer to $300, can transmit, but isn't Full Duplex. The LimeSDR (the original one) can also be had for around that price, and has two RX and TX full duplex channels, but not a whole lot of RF front end. HackRF would, however, work for the fan project.
- rasz 9y agoyou confuse Full Duplex with transceiver. RTL-SDR is receiver, hackrf is transceiver(receiving and transmitting, but not at the same time), lime is full duplex(can TX and RX at the same time).
- fpgaminer 9y agoYou're right, I misspoke. All I needed was a transceiver (or even just separate TX). Regardless, you can't even get a SDR transceiver for an affordable price.