RC receiver to arduino converter for BB-8

Ask Hackaday: How Do You Convert Negative Voltages To Positive?

November 14, 2016 by Steven Dufresne 81 Comments

I have a good background working with high voltage, which for me means over 10,000 volts, but I have many gaps when it comes to the lower voltage realm in which RC control boards and H-bridges live. When working on my first real robot, a BB-8 droid, I stumbled when designing a board to convert varying polarities from an RC receiver board into positive voltages only for an Arduino.

Today’s question is, how do you convert a negative voltage into a positive one?

In the end I came up with something that works, but I’m sure there’s a more elegant solution, and perhaps an obvious one to those more skilled in this low voltage realm. What follows is my journey to come up with this board. What I have works, but it still nibbles at my brain and I’d love to see the Hackaday community’s skill and experience applied to this simple yet perplexing design challenge.

The Problem

I have an RC receiver that I’ve taken from a toy truck. When it was in the truck, it controlled two DC motors: one for driving backwards and forwards, and the other for steering left and right. That means the motors are told to rotate either clockwise or counterclockwise as needed. To make a DC motor rotate in one direction you connect the two wires one way, and to make it rotate in the other direction you reverse the two wires, or you reverse the polarity. None of the output wires are common inside the RC receiver, something I discovered the hard way as you’ll see below.

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Electronica 2016: Too Much Electronics

November 14, 2016 by Elliot Williams 34 Comments

The Electronica trade show in Munich is so big that it only takes place once every two years. Every manufacturer, distributor, and maker of anything electronic is there. To get a feel for the scale of things, Electronica is spread out over twelve large exhibition halls and is served by two separate subway stations, one on either end. You wouldn’t think there would be so many inductor manufacturers in the world, but you’d be wrong.

It’s a hardware geek’s paradise, even if it is aimed more at facilitating industry contacts than at serving the humble hacker. But it’s great to see what is out there, quiz reps of all our favorite chip manufacturers about what they’ve got going on, and just generally wander around. You might not get to play with the multi-gigahertz scopes on a day-to-day basis, but you can get hands-on with them at Electronica. And as cool as it is to talk directly to the representatives of our mega-manufacturers, it’s maybe more fun to check up on the creative fringe of companies that you’ve never heard of before, but who nonetheless have great ideas.
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Linux On Your NES Classic Edition

November 13, 2016 by Jenny List 53 Comments

Nintendo look as though they may have something of a hit on their hands with their latest console offering. It’s not the next in the line of high-end consoles with immersive VR or silicon that wouldn’t have looked out of place in last year’s supercomputer, instead it’s an homage to one of their past greats. The NES Classic Edition is a reboot of the 1980s console with the familiar styling albeit a bit smaller, and 30 of the best NES games included.

You do not, however, get an original NES with a 6502 derived processor, and a stack of game cartridges. In the Classic Edition is a modern emulator, running on very modern hardware. We’re told it contains an Allwinner R16 quad-core Cortex A7 SoC, 256Mb of RAM, and 512Mb of Flash. That’s a capable system, and unsurprisingly any hacking potential it may have has attracted some interest. Reddit user [freenesclassic] for example has been investigating its potential as a Linux machine, and has put up a post showing the progress so far. It is known that there is already some form of Linux underpinning the console because Nintendo have released a set of sources as part of their compliance with the terms of the relevant open-source licences. That and the availability of a serial port via pads on the PCB gives hope that a more open distro can be installed on it.

We’re taken through the process of starting the machine up with the serial port connected to a PC, and getting it into the Allwinner FEL mode for low-level flashing work. Then we’re shown the process of loading a custom U-Boot, from which in theory a kernel of your choice can be loaded.

Of course, it’s not quite that simple. There is still some way to go before the device’s Flash can be accessed so for now, all that is possible is to use the RAM, and the current state of play has a kernel panic as it is unable to mount a filesystem. However this is a new piece of hardware in its first few days after launch, so this is very much a work in progress. We are sure that this device will in time be opened up as a fully hackable piece of hardware, and we look forward to covering the interesting things people do with it when that has happened.

If you are interested in the NES Classic, take a look at it on Nintendo’s web site. Meanwhile, here at Hackaday as a quick look at our past stories tagged “nes” shows, we’ve covered a huge number of projects involving the platform in the past.

Thanks [Doc Oct] for the tip.

Original NES console header image: Evan-Amos [Public domain], via Wikimedia Commons.

Transparent Rocket Engine

November 12, 2016 by Manuel Rodriguez-Achach 45 Comments

Rocket engines are undeniably cool. Experiencing the roar, seeing the fire, and watching the rocket blast off into the sky… what else can you ask for? Well, for [NightHawkInLight], a transparent rocket body is the answer.

Based on previous work by [Applied Science], he uses an acrylic rod as the rocket body and as the fuel. Bring a flame into the acrylic, apply oxygen from a canister at the other end of the body and voilà! The rocket engine starts nicely, and even better, the intensity of the burn can be controlled via the amount of oxygen provided.
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ArduWorm: A Malware For Your Arduino Yun

November 11, 2016 by Elliot Williams 24 Comments

We’ve been waiting for this one. A worm was written for the Internet-connected Arduino Yun that gets in through a memory corruption exploit in the ATmega32u4 that’s used as the serial bridge. The paper (as PDF) is a bit technical, but if you’re interested, it’s a great read. (Edit: The link went dead. Here is our local copy.)

The crux of the hack is getting the AVR to run out of RAM, which more than a few of us have done accidentally from time to time. Here, the hackers write more and more data into memory until they end up writing into the heap, where data that’s used to control the program lives. Writing a worm for the AVR isn’t as easy as it was in the 1990’s on PCs, because a lot of the code that you’d like to run is in flash, and thus immutable. However, if you know where enough functions are located in flash, you can just use what’s there. These kind of return-oriented programming (ROP) tricks were enough for the researchers to write a worm.

In the end, the worm is persistent, can spread from Yun to Yun, and can do most everything that you’d love/hate a worm to do. In security, we all know that a chain is only as strong as its weakest link, and here the attack isn’t against the OpenWRT Linux system running on the big chip, but rather against the small AVR chip playing a support role. Because the AVR is completely trusted by the Linux system, once you’ve got that, you’ve won.

Will this amount to anything in practice? Probably not. There are tons of systems out there with much more easily accessed vulnerabilities: hard-coded passwords and poor encryption protocols. Attacking all the Yuns in the world wouldn’t be worth one’s time. It’s a very cool proof of concept, and in our opinion, that’s even better.

Thanks [Dave] for the great tip!

Listening To Jupiter On A DIY Radio

November 10, 2016 by Al Williams 41 Comments

By Jove, he built a radio!

If you want to get started with radio astronomy, Jupiter is one of the easiest celestial objects to hear from Earth. [Vasily Ivanenko] wanted to listen, and decided to build a modular radio receiver for the task. So far he’s written up six of the eight planned blog posts.

The system uses an LNA, a direct conversion receiver block, and provides audio output to a speaker, output to a PC soundcard, and a processed connection for an analog to digital converter. The modules are well-documented and would be moderately challenging to reproduce.

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Drone Snags A Snag, Pilot Faces Fine

November 10, 2016 by Jenny List 38 Comments

If you hail from somewhere to which Australian beers have been exported, you could be forgiven for forming a view of the country based solely on TV adverts for Foster’s, or Castlemaine XXXX. Entertaining 30-second stories of wily young Aussies, and their inventive schemes to get their hands on a cool glass of the Amber Nectar.

Whether it’s an accurate depiction or not is something you’d have to ask an Australian, but it seems to provide a blueprint for at least some real-life stories. An Australian man in Sunbury, west of Melbourne, is to face a fine of up to A$9000 for using his multirotor to pick up a sausage in a bun from a stall in a superstore car park, and deliver it to him relaxing in his hot tub.

From one perspective the video of the event which we’ve posted below the break is a very entertaining film. We see the flight over houses and a main road to a local branch of Bunnings, an Australian hardware store chain. Their sausage sizzle is a weekly institution in which local non-profit groups sell barbecued sausages from a stall in the car park as a fundraiser. The drone lowers a bag on a string over people queuing, with a note saying “Please buy snag(Aussie slang for sausage) and put in bag, here’s $10”. Someone complies, and the tasty treat is flown back over suburbia to our hero in his tub. It’s fairly obviously a production with many takes and supporting actors rather than a real continuous flight, but the Australian Civil Aviation Safety Authority is nevertheless investigating it. Breaches of the rules are reported as being use of a drone within 30 metres of people, as well as flight beyond the line of sight and over a populated area. The original video has been taken down, but it lives on courtesy of Australian tech site EFTM.

Aside from providing our readership with entertainment courtesy of our Australian friends there is an important message to take away from this story. It’s likely that if they can adequately prove that their flight was never out of the line of sight they can escape some of the charges, but even so they have strayed into difficult territory. We’ve written about drone hysteria on the part of authorities before, and we are living in an age during which twitchy agencies have shown themselves willing to view what we know to be little more than grown-up toys as something akin to terror weapons. Of course people who use multirotors for wilful endangerment should be brought to book in no uncertain terms, but the line between that and innocuous use feels sometimes to have been shifted in an alarming direction. Please keep entertaining us with your multirotor exploits and hacks, but never take your eye off how what you are doing could be misconstrued by those in authority. We’d prefer not to be writing up drone stories involving fines.

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