3D Printering: Which Raspberry Pi Is Best At Slicing In Octoprint?

May 3, 2018 by Tom Nardi 22 Comments

OctoPrint is arguably the ultimate tool for remote 3D printer control and monitoring. Whether you simply want a way to send G-Code to your printer without it being physically connected to your computer or you want to be able to monitor a print from your phone while at work, OctoPrint is what you’re looking for. The core software itself is fantastic, and the community that has sprung up around the development of OctoPrint plugins has done an incredible job expanding the basic functionality into some very impressive new territory.

RAMBo 3D controller with Pi Zero Integration

But all that is on the software side; you still need to run OctoPrint on something. Technically speaking, OctoPrint could run on more or less anything you have lying around the workshop. It’s cross platform and doesn’t need anything more exotic than a free USB port to connect to the printer, and people have run it on everything from disused Windows desktops to cheap Android smartphones. But for many, the true “home” of OctoPrint is the Raspberry Pi.

As I’ve covered previously, the Raspberry Pi does make an exceptional platform for OctoPrint. Given the small size and low energy requirements of the Pi, it’s easy to integrate into your printer. The new Prusa i3 MK3 even includes a header right on the control board where you can plug in a Raspberry Pi Zero.

But while the Raspberry Pi is more than capable of controlling a 3D printer in real-time, there has always been some debate about its suitability for slicing STL files. Even on a desktop computer, it can sometimes be a time consuming chore to take an STL file and process it down to the raw G-Code file that will command the printer’s movements.

In an effort to quantify the slicing performance on the Raspberry Pi, I thought it would be interesting to do a head-to-head slicing comparison between the Pi Zero, the ever popular Pi 3, and the newest Pi 3 B+.

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Directly Executing Chunks Of Memory: Function Pointers In C

May 2, 2018 by Sven Gregori 75 Comments

In the first part of this series, we covered the basics of pointers in C, and went on to more complex arrangements and pointer arithmetic in the second part. Both times, we focused solely on pointers representing data in memory.

But data isn’t the only thing residing in memory. All the program code is accessible through either the RAM or some other executable type of memory, giving each function a specific address inside that memory as entry point. Once again, pointers are simply memory addresses, and to fully utilize this similarity, C provides the concept of function pointers. Function pointers provide us with ways to make conditional code execution faster, implement callbacks to make code more modular, and even provide a foothold into the running machine code itself for reverse engineering or exploitation. So read on!

Function Pointers

In general, function pointers aren’t any more mysterious than data pointers: the main difference is that one references variables and the other references functions. If you recall from last time how arrays decay into pointers to their first element, a function equally decays into a pointer to the address of its entry point, with the () operator executing whatever is at that address. As a result, we can declare a function pointer variable fptr and assign a function func() to it: fptr = func;. Calling fptr(); will then resolve to the entry point of function func() and execute it.

Admittedly, the idea of turning a function into a variable may seem strange at first and might require some getting used to, but it gets easier with time and it can be a very useful idiom. The same is true for the function pointer syntax, which can be intimidating and confusing in the beginning. But let’s have a look at that ourselves.

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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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