THP Entry: A 433MHz Packet Cloner

ookloneThe first generation of The Internet Of Things™ and Home Automation devices are out in the wild, and if there’s one question we can ask it’s, “why hasn’t anyone built a simple cracking device for them”. Never fear, because [texane] has your back with his cheap 433MHz OOK frame cloner.

A surprising number of the IoT and Home Automation devices on the market today use 433MHz radios, and for simplicity’s sake, most of them use OOK encoding. [Texane]’s entry for THP is a simple device with two buttons: one to record OOK frames, and a second to play them back.

Yes, this project can be replicated with fancy software defined radios, but [Texane]’s OOKlone costs an order of magnitude less than the (actually very awesome) HackRF SDR. He says he can build it for less than $20, and with further refinements to the project it could serve as a record and play swiss army knife for anything around 433MHz. Video demo of the device in action below.

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Verifying A Wireless Protocol With RTLSDR

rtlsdr_nrf905_rtlizer

[Texane] is developing a system to monitor his garage door from his apartment. Being seven floors apart, running wires between the door and apartment wasn’t an option, so he turned to a wireless solution. Testing this wireless hardware in an apartment is no problem, but testing it in situ is a little more difficult. For that, he turned to software defined radio with an RTLSDR dongle.

The hardware for this project is based around a TI Stellaris board and a PTR8000 radio module. All the code for this project was written from scratch (Github here), making it questionable if the code worked on the first try. To test his code, [Texane] picked up one of those USB TV tuner dongles based around the RTL2832U chipset. This allowed him to monitor the frequencies around 433MHz for the packets his hardware should be sending.

After that, the only thing left to do was to write a frame decoder for his radio module. Luckily, the datasheet for the module made this task easy.

[Texane] has a frame decoder for the NRF905 radio module available in his Git. It’s not quite ready for serious applications, but for testing a simple radio link it’s more than enough.