The Future Of The Internet Of Things

November 16, 2014 by Brian Benchoff 81 Comments

When buying anything, you’re going to have a choice: good, fast, or cheap. Pick any two. A plumber will fix a drain good and fast, but it won’t be cheap. The skeezy guy you can call will fix a drain fast and cheap, but it won’t be good.

Such it is with radios. You can have long-range (good), high bandwidth (fast), or a low price (cheap). Pick any two. The Internet of Things demands a cheap, long-range radio module, but until now this really hasn’t existed. At Electronica last week, Microchip demoed their IoT solution, the LoRa. This module has a 15km (rural) or ~3km (heavy urban) range, works for a year on two AAA batteries, and is very cheap. Bandwidth? That’s crap, but you’re not streaming videos to your shoe.

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Morse Decoder’s Lean And Sexy Search Algorithm

November 15, 2014 by Mike Szczys 27 Comments

Often the Morse Code centered projects that we feature are to help you practice transmitting messages. This one takes a tack and builds an automatic decoder. We think [Nicola Cimmino’s] project is well worth featuring simply based on his explanation of the Digital Signal Processing used on the signal coming in from the microphone. Well done. But he’s really just getting warmed up.

What makes this really stand out is a brilliant algorithm that allows conversion from Morse to ASCII using a lookup table of only 64 bytes. This provides enough room for A-Z and 0-9 without chance of collision but could be expanded to allow for more characters. Below is a concise description of how the algorithm works but make sure you take the time to read [Nicola’s] project description in its entirety.

The algorithm can be decribed as follows. Have an index inside the lookup string inizialied to zero. Have an initial dash jump size of 64. At every received element (dot or dash) halve the initial dash jump and then increase by 1 the index inside the lookup string if a dot was received and by dash jump size if a dash was received. Repeat until a letter separator is reached, at that point the index inside the lookup string will point to the ASCII corresponding to the decoded morse.

Have you heard of this technique before? If so, tell us about it in the comments below. Before you jump all over this one, realize that Magic Morse uses a different technique.

$2 FM Transmitter For Raspberry Pi

November 12, 2014 by Elliot Williams 37 Comments

We love re-purposed consumer gear. This project uses a cheap, discontinued cellphone gadget to create a Raspberry Pi controlled FM radio transmitter.

The Sony-Ericsson MMR-70 radio transmitter apparently used to connect to a cell phone and broadcast music. But the Walkman cellphones in question are a little bit old in the tooth, so one can buy the transmitter units for cheap on the resale market. What makes the transmitters even more interesting is that you can activate and deactivate the radio, change frequency or output power, and even send RDS station and song information.

It turns out (link in German) that the radios have an AVR ATMega32 microcontroller and a NS73 radio transmitter module, which can be entirely controlled over I2C. (Schematic here as PDF.) The units also have handy test points strewn all around. Once the test points were mapped out, one could completely ignore the on-board AVR microcontroller and control the FM transmitter module directly using the Raspberry Pi’s I2C outputs.

And that’s where [Manawyrm] stepped in. She wrote an I2C daemon for the Raspberry Pi that lets you control the FM transmitter via simple commands. All you have to do is solder up a bunch of test points, install [Manawyrm]’s software, write a batch script, and you’re on the air. For instance, this makes building a FM radio retransmitter for online streamed audio a one-day project. You can see his working example on youtube. Of course, you’ll want a web-based remote control interface to go with that.

If you’re interested in hacking along, and don’t have a Raspberry Pi application in mind, Sparkfun used to sell the NS73 radio transmitter so you can find lots of good information about the chip. We’d love to see a stand-alone broadcasting gizmo that actually utilizes the onboard AVR chip, but our hats are off to [Manawyrm] for making the Raspberry Pi version so accessible.

Transmitting Data Long-Distance With Morse Code

November 12, 2014 by Ethan Zonca 61 Comments

[Konstantinos] wrote in to tell us about his CDW project: a digital encoding scheme for ham radio that uses CW (continuous wave) Morse code for digital data transfer. [Link updated 1/5/16] CW operation with Morse code is great for narrow-bandwidth low-speed communication over long distances. To take advantage of this, [Konstantinos] developed a program that takes binary or text files, compresses them, and translates them to a series of letters and numbers that can be represented with Morse code.

The software translates the characters into sequences of Morse code pulses, and plays an audio stream of the result. His software doesn’t support decoding Morse from an audio stream, so [Konstantinos] recommends using one of many existing programs to get the job done. Alternatively those with a good ear and working knowledge of Morse can transcribe the characters by hand.

After receiving a broadcast, the user pastes received characters back in the software. The software re-assembles the binary file from the Morse characters and decompresses the result. [Konstantinos] also added a simple XOR encryption feature, but keep in mind that using encryption on ham radio bands is technically illegal.

Fox Hunting With A Raspberry Pi

November 6, 2014 by Bryan Cockfield 11 Comments

No, not a real fox! [KM4EFP] is a ham radio operator with a passion for fox hunting, which is an event where several radio operators attempt to find a broadcasting beacon (a “fox”) using radio direction finding techniques. [KM4EFP] has just built his own portable fox using a Raspberry Pi in a very well-built enclosure.

Since the fox could be outside for a while, the project was housed in a reasonably weatherproof ammunition case. A mount for an antenna was attached to the side, and it is hooked up to a GPIO pin on the Raspberry Pi. The entire device is powered by a 6000 mAh battery pack which allows the fox to broadcast long enough to be found.

The software running on the Raspberry Pi is very similar to the Pi FM transmitter program but it is specially made for ham radio broadcasting instead. Almost no extra hardware is needed to get the Pi broadcasting radio, as these software packages can drive the antenna directly from the GPIO pin. This is a great twist on the standard FM transmitter that ham radio enthusiasts everywhere can use to start finding those wily foxes!

SDR: Satellite Death Receiver

November 4, 2014 by Kristina Panos 18 Comments

Halloween may be over, but [happysat] has found a way to listen to the dead. Satellites, that is, specifically those in the 136-138 MHz and 150-400 MHz ranges. He’s using an RTL-SDR dongle and a QFH antenna to detect the death throes of decommissioned navigation and space research satellites.

[happysat] was listening to NOAA/Meteor on the 137MHz band when he made this discovery. When a satellite is near end of life, the last bit of fuel is used to push it into graveyard orbit. This doesn’t always work, however, and when the light is just right, a chemical reaction makes the long-dead batteries conduct and these satellites in purgatory transmit once more.

They’re not sending out anything ~~proprietary~~ useful, just unmodulated carrier that sometimes interferes with currently operational satellites on the 136-138 MHz band. [happysat] captured some audio from two of the oldest satellites that are still broadcasting, and links to a TLE set of dead satellites he created. Check out his frequency database for SDR# as well. Don’t have a weather satellite-capable antenna? Build one!

[via /r/RTLSDR]

The Internet Of Things Chip Gets A New Spectrum

October 20, 2014 by Brian Benchoff 52 Comments

Last year we learned about Weightless, an Internet of Things chip that solves all the problems of current wireless solutions. It’s low power and has a 10-year battery life (one AA cell), the hardware should cost around $2 per module, and the range of the Weightless devices range from 5+km in urban environments to 20-30km in rural environments. There haven’t been many public announcements from the Weightless SIG since the specification was announced, but today they’re announcing Weightless will include an additional spectrum, the 868/915 MHz ISM spectrum.

The original plan for Weightless was to use the spectrum left behind by UHF TV – between 470 and 790MHz. Regulatory agencies haven’t been moving as fast as members of the Weightless SIG would have hoped, so now they’re working on a slightly different design that uses the already-allocated ISM bands. They’re not giving up on the TV whitespace spectrum; that’s still part of the plan to put radio modules in everything. The new Weightless-N will be available sooner, though, with the first publicly available base station, module, and SDK arriving sometime next spring.

Weightless has put up a video describing their new Weightless-N hardware; you can check that out below. If you want the TL;DR of how Weightless can claim such a long battery life and huge range from an Internet of Things radio module, here’s an overly simplified explanation: power, range, and bandwidth. Pick any two.

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