Accessing Blockchain On ESP8266 Using The NodeMCU Board

May 2, 2018 by Sean Boyce 24 Comments

Blockchains claim to be public, distributed, effectively immutable ledgers. Unfortunately, they also tend to get a little bit huge – presently the Bitcoin blockchain is 194GB and Ethereum weighs in at 444GB. That poses quite an inconvenience for me, as I was looking at making some fun ‘Ethereum blockchain aware’ gadgets and that’s several orders of magnitude too much data to deal with on a microcontroller, not to mention the bandwidth cost if using 3G.

Having imagined a thin device that I could integrate into my mobile phone cover (or perhaps… a wallet?) dealing with the whole blockchain was clearly not a possibility. I could use a VPS or router to efficiently download the necessary data and respond to queries, but even that seemed like a lot of overhead, so I investigated available APIs.

As it turns out, several blockchain explorers offer APIs that do what I want. My efforts get an ESP8266 involved with the blockchain began with two of the available APIs: Ethplorer and Etherscan.

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When 4 + 1 Equals 8: An Advanced Take On Pointers In C

April 19, 2018 by Sven Gregori 104 Comments

In our first part on pointers, we covered the basics and common pitfalls of pointers in C. If we had to break it down into one sentence, the main principle of pointers is that they are simply data types storing a memory address, and as long as we make sure that we have enough memory allocated at that address, everything is going to be fine.

In this second part, we are going to continue with some more advanced pointer topics, including pointer arithmetic, pointers with another pointer as underlying data type, and the relationship between arrays and pointers. But first, there is one particular pointer we haven’t talked about yet.

The one proverbial exception to the rule that pointers are just memory addresses is the most (in)famous pointer of all: the NULL pointer. Commonly defined as preprocessor macro (void *) 0, we can assign NULL like any other pointer.

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Circuit VR: The Dickson Charge Pump

April 6, 2018 by Al Williams 23 Comments

There was a time when taking a low DC voltage — say a single battery — and converting it to a higher voltage was painful. Now, however, cheap and easy-to-use DC to DC converters are readily available. For some small tasks, though, these can seem like overkill. For example, consider a case where you need to supply a higher voltage for a MOSFET gate that doesn’t draw much current. Perhaps you need that higher voltage to trigger a microcontroller’s programming mode and nothing else. The current draw is minimal, and a full-blown DC to DC converter is overkill. For cases like that, it is tempting to use some voltage multiplication scheme. There are many, but for this post, I’m going to take you inside a Dickson charge pump. This is Circuit VR because not only are we going to discuss the circuit, we’ll look at an LT Spice simulation you can try yourself.

The Dickson is interesting because it doesn’t require any AC conversion or transformers. Instead, it uses diodes or other switching elements to transfer charge between capacitors in stages. Each stage will effectively increase the voltage by the supply voltage — in theory. Reality isn’t so kind, though, as we’ll see.

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Bringing Fiction To Life With 3D Printing

April 2, 2018 by Tom Nardi 27 Comments

I print something nearly every day, and over the last few years, I’ve created hundreds of practical items. Parts to repair my car, specialized tools, scientific instruments, the list goes on and on. It’s very difficult for me to imagine going back to a time where I didn’t have the ability to rapidly create and replicate physical objects at home. I can say with complete honesty that it has been an absolutely life-changing technology for me, personally.

But to everyone else in my life, my friends and family, 3D printers are magical boxes which can produce gadgets, weapons, and characters from their favorite games and movies. Nobody wants to see the parts I made to get my girlfriend’s 1980’s Honda back on the road before she had to go to work in the morning, they want to see the Minecraft block I made for my daughter. I can’t get anyone interested in a device I made to detect the algal density of a sample of water, but they all want me to run off a set of the stones from The Fifth Element for them.

As I recently finished just such a project, a 3D printed limpet mine from Battlefield 1, I thought I would share some thoughts on the best practices for turning fiction into non-fiction.

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The Essential List Of 3D Printer Accessories

March 28, 2018 by Tom Nardi 108 Comments

You’ve acquired your first 3D printer and are giddy with excitement. But like all new additive manufacturing adventurers, the more you do with your printer the more questions arise. Don’t worry, we’ve got your back.

Getting the most out of your time with a new 3D printer has a lot to do with the tools and accessories on hand and what you do with them. Let’s take a look at a few of the accessories that should accompany every 3D printer, be it in your home, school, or hackerspace. There’s already enough potential aggravation when it comes to 3D printing, the goal here is to ensure you won’t be without a tool or supply when you need it the most.

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An Introduction To Storm Detector Modules

March 22, 2018 by Sean Boyce 41 Comments

Lightning storm detectors have been around for a surprisingly long time. The early designs consisted of a pair of metal bells and a pendulum. When there was a charge applied, for example by connecting one bell to the ground and the other to a lightning rod, the bells would ring when a lightning storm was close by. In the mid 18^th century, these devices were only practical for demonstration and research purposes, but very likely represent the earliest devices that convert electrostatic charge to mechanical force. A bit over a hundred years later, the first lightning detector was considered by some as the first radio receiver as well.

As soon as I found out about storm detector chips, I knew I would have to get one working. For about $25, I ordered an AMS AS3935 module from China. This chip has been featured before in a number of excellent projects such as Twittering lightning detectors, and networks of Sub-Saharan weather stations. While there’s an Arduino library for interfacing with this IC, I’m going to be connecting it up to an ESP8266 running the NodeMCU firware, which means digging into the datasheet and writing some SPI code. If any of the above tickles your fancy, read on! Continue reading “An Introduction To Storm Detector Modules” →

CUDA Is Like Owning A Supercomputer

March 19, 2018 by Al Williams 51 Comments

The word supercomputer gets thrown around quite a bit. The original Cray-1, for example, operated at about 150 MIPS and had about eight megabytes of memory. A modern Intel i7 CPU can hit almost 250,000 MIPS and is unlikely to have less than eight gigabytes of memory, and probably has quite a bit more. Sure, MIPS isn’t a great performance number, but clearly, a top-end PC is way more powerful than the old Cray. The problem is, it’s never enough.

Today’s computers have to processes huge numbers of pixels, video data, audio data, neural networks, and long key encryption. Because of this, video cards have become what in the old days would have been called vector processors. That is, they are optimized to do operations on multiple data items in parallel. There are a few standards for using the video card processing for computation and today I’m going to show you how simple it is to use CUDA — the NVIDIA proprietary library for this task. You can also use OpenCL which works with many different kinds of hardware, but I’ll show you that it is a bit more verbose.
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