Akiba’s Awesome Lighting Tutorial

November 19, 2015 by Nava Whiteford 3 Comments

[Akiba] over at FreakLabs just put up a detailed tutorial outlining how to control and sequence lighting wirelessly using an Arduino and Vixen lighting sequencer software.

For those that don’t know [Akiba], he’s the guy behind Wrecking Crew Orchestra (TRON Dance) and their EL wire costumes. [Akiba] hacks on his projects at Hacker farm out in rural Japan.

In the tutorial, he sets up a simple 6 LED circuit on a Fredboard (an Arduino compatible board with integrated breadboard). [Akiba] then describes configuring the Vixen sequencer software to control the Arduino, providing simple example code to decode the Vixen serial protocol. Finally [Akiba] shows how to use the ChibiArduino protocol stack to build a wireless illumination system.

[Akiba] has used these tools in many stage performances including with the Wrecking Crew Orchestra (shown above) and the world number 1 flair bartending crew, UPT.

This tutorial is particularly awesome, as it includes both step-by-step videos and a text reference. The videos give a great overview of the process, while the text provides a handy reference to refer to as you hack on your own illumination projects.

Thanks for the writeup [Akiba]! With Christmas just round the corner we hope to see readers using these techniques in their own festive illuminations soon!

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Audio-coupled Smoke Alarm Interface Sends Texts, Emails

November 16, 2015 by Dan Maloney 18 Comments

The Internet of Things is getting to be a big business. Google’s Nest brand is part of the trend, and they’re building a product line that fills niches and looks good doing it, including the Nest Protect smoke and CO detector. It’s nice to get texts and emails if your smoke alarm goes off, but if you’d rather not spend $99USD for the privilege, take a look at this $10 DIY smoke alarm interface.

The secret to keeping the cost of [Team SimpleIOThings’] interface at a minimum is leveraging both the dirt-cheap ESP8266 platform and the functionality available on If This Then That. And to keep the circuit as simple and universal as possible, the ESP8266 dev board is interfaced to an existing smoke detector with a simple microphone sensor. From what we can see it’s just a sound level sensor, and that should work fine with the mic close to the smoke detector. But with high noise levels in your house, like those that come with kids and dogs, false alarms might be an issue. In that case, we bet the software could be modified to listen for the Temporal-Three pattern used by most modern smoke detectors. You could probably even add code to send a separate message for a CO detector sounding a Temporal-Four pattern.

Interfacing to a smoke detector is nothing new, as this pre-ESP8266 project proves. But the versatile WiFi SoC makes interfaces like this quick and easy projects.

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Polyakov Direct Digital Synthesis Receiver

November 15, 2015 by Al Williams 4 Comments

Direct conversion receivers are popular among ham radio operators and others who build radios. Suppose you want to listen to a signal at 7.1 MHz. With a direct conversion receiver, you’d tune a local oscillator to 7.1 MHz, and mix it with the incoming signal. The resulting sum and differences of the input frequencies will include the audio of an AM signal on the desired frequency.

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VOCore Tutorial Gets You Started With Tiny Router

November 15, 2015 by Elliot Williams 18 Comments

[Vadim] wrote up this short but sweet tutorial on getting started with the Vocore (tiny) OpenWRT-router-on-a-stamp. If you need more computing power than you can get with an ESP8266, and you want an open-source Linux-plus-Wifi solution in a square inch of board space, the Vocore looks pretty sweet.

We covered the Vocore a while ago. It has 28 GPIOs, all accessible from system calls in OpenWRT. It becomes much more computer-like if you add a dock that breaks out the USB and Ethernet functionality, but that also doubles the price.

Getting started with a no-frills Linux box (chip?) can be intimidating. So it’s a good thing that [Vadim] details a first setup of the Vocore over WiFi and SSH, and then takes you through a button-and-LED style ‘Hello World’ application that makes simple use of the GPIOs.

He says he’s going to interface it eventually with a TI CC110 sub-gig radio unit, but that’s going to involve writing some drivers and will take him some time. We’d love to see how to connect peripherals, so we’re waiting with bated breath.

[Vadim] also helpfully included an un-bricking script for the Vocore, which restores the default firmware and gets you out of whatever hole you’ve managed to dig yourself into. Basically, you connect to the device over a USB-Serial adapter, run his script, and you should be set.

Any of you out there using a Vocore? Or other OpenWRT routers? Give [Vadim]’s tutorial a glance and let us know what you think.

RFM69 To MQTT Gateway On The Super-Cheap

November 14, 2015 by Elliot Williams 10 Comments

[Martin] is working on a RFM69-to-MQTT bridge device. If you’re at all interested in DIY home automation, this is going to be worth following. Why? When your home automation network gets big enough, you’re going to have to think seriously about how the different parts talk to each other. There are a number of ways to handle this messaging problem, but MQTT is certainly a contender.

MQTT is a “lightweight” publish-subscribe framework that’s aimed at machine-to-machine data sharing, and runs on top of a normal TCP/IP network. IBM has been a mover behind MQTT since the beginning, and now Amazon is using it too.

But most MQTT servers need a TCP/IP network, which pretty much means WiFi, and this can be a killer for remote sensors that you’d like to run on battery power, or with limited processing power. For these use cases, a low-power, simple sub-gigahertz radio module is a better choice than WiFi. But then how to do you get your low-power radios to speak to your MQTT devices?

That’s the point of [Martin]’s MQTT bridge. Previously he had built a sub-gig radio add-on for a Raspberry Pi, and let the Pi handle the networking. But it looks like there’s enough processing power in a lowly ESP8266 to handle the MQTT side of things (over WiFi, naturally). Which means that you could now connect your 868 MHz radio devices to MQTT for less than the cost of two pumpkin spice, double-pump lattes.

On the firmware side, [Martin] has enlisted the help of [Felix], who developed the Arduino-plus-RFM69 project, the Moteino. [Felix] has apparently ported his RFM69 library to the ESP8266. We’re dying to see this working.

For now, we’ve got some suggestive screenshots which hint at some LAN-exposed configuration screens. We’re especially interested in the RFM + MQTT debug console window, which should really help in figuring out what’s gone wrong in a system that spans two radio protocols.

The bottom line of all of this? Super-cheap, power-efficient RFM69-based radio nodes can talk with your sophisticated MQTT network. Keep your eyes on this project.

Low Parts Count ARM SDR

November 14, 2015 by Al Williams 4 Comments

[Alberto di Bene] wanted to build an SDR for relatively low frequencies. Usually, you’d start with some front end to get the radio frequency signal down where you can work with it. But [Alberto] practically just fed an antenna into an STM32F429 Discovery board and did all the radio processing in the onboard ARM chip.

There is a little more to it than that, but only a little. If you open the PDF file on [Alberto’s] site, you’ll see there is a simple front end filter (a transformer, along with a few capacitors and inductors). This low pass filter prevents high frequencies from reaching the ARM processor’s analog to digital converter. In addition, a capacitor and a couple of resistors ensure the converter only sees positive voltages.

The CPU digitizes the incoming signal and processes it, demodulating several different types of radio transmission. The recovered audio is sent through the onboard digital to analog converter.

In addition to an input filter, the output also needs a filter to prevent high frequencies from reaching the speaker. Unlike the input filter, this one is a bit more complicated. The inductors needed for a passive filter were too large to be practical, so the output filter is an active one with a few transistors. The only other external circuitry is the power supply for the Discovery board.

The document does a great job of explaining the rationale behind the design choices and how the whole system works. It also includes simulations of both analog and digital filters used in the design.

This is really bare metal SDR and reading the code is educational. However, if you want to start with something simpler, consider GNU Radio and either an SDRPlay or a cheap RTL-SDR dongle.

Your First GNU Radio Receiver With SDRPlay

November 12, 2015 by Al Williams 25 Comments

Although GRC (the GNU Radio Companion) uses the word radio, it is really a graphical tool for building DSP applications. In the last post, I showed you how you could experiment with it just by using a sound card (or even less). However, who can resist the lure of building an actual radio by dragging blocks around on a computer screen?

For this post and the accompanying video, I used an SDRPlay. This little black box has an antenna jack on one end and a USB port on the other. You can ask it to give you data about a certain area of the RF spectrum and it will send complex (IQ) data out in a form that GRC (or other DSP tools) can process.

The SDRPlay is a great deal (about $150) but if you don’t want to invest in one there are other options. Some are about the same price (like the HackRF or AirSpy) and have different features. However, you can also use cheap TV dongles, with some limitations. The repurposed dongles are not as sensitive and won’t work at lower frequencies without some external help. On the other hand, they are dirt cheap, so you can overlook a few little wrinkles. You just can’t expect the performance you’ll get out of a more expensive SDR box. Some people add amplifiers and converters to overcome these problems, but at some point it would be more cost effective to just spring for a more expensive converter.