Skills

354 Articles

Networking: Pin The Tail On The Headless Raspberry Pi

April 18, 2017 by 69 Comments

Eager to get deeper into robotics after dipping my toe in the water with my BB-8 droid, I purchased a Raspberry Pi 3 Model B. The first step was to connect to it. But while it has built-in 802.11n wireless, I at first didn’t have a wireless access point, though I eventually did get one. That meant I went through different ways of finding it and connecting to it with my desktop computer. Surely there are others seeking to do the same so let’s take a look at the secret incantations used to connect a Pi to a computer directly, and indirectly.

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Introduction To TensorFlow

April 11, 2017 by 26 Comments

I had great fun writing neural network software in the 90s, and I have been anxious to try creating some using TensorFlow.

Google’s machine intelligence framework is the new hotness right now. And when TensorFlow became installable on the Raspberry Pi, working with it became very easy to do. In a short time I made a neural network that counts in binary. So I thought I’d pass on what I’ve learned so far. Hopefully this makes it easier for anyone else who wants to try it, or for anyone who just wants some insight into neural networks.

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PlatformIO And Visual Studio Take Over The World

April 7, 2017 by 40 Comments

In a recent post, I talked about using the “Blue Pill” STM32 module with the Arduino IDE. I’m not a big fan of the Arduino IDE, but I will admit it is simple to use which makes it good for simple things.

I’m not a big fan of integrated development environments (IDE), in general. I’ve used plenty of them, especially when they are tightly tied to the tool I’m trying to use at the time. But when I’m not doing anything special, I tend to just write my code in emacs. Thinking about it, I suppose I really don’t mind an IDE if it has tools that actually help me. But if it is just a text editor and launches a few commands, I can do that from emacs or another editor of my choice. The chances that your favorite IDE is going to have as much editing capability and customization as emacs are close to zero. Even if you don’t like emacs, why learn another editor if there isn’t a clear benefit in doing so?

There are ways, of course, to use other tools with the Arduino and other frameworks and I decided to start looking at them. After all, how hard can it be to build Arduino code? If you want to jump straight to the punch line, you can check out the video, below.

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An Introduction To Differential I²C

March 31, 2017 by 45 Comments

A few weeks back, we talked about the no-nos of running I²C over long wires. For prototyping? Yes! But for a bulletproof production environment, this practice just won’t make the cut. This month I plucked my favorite solution from the bunch and gave it a spin. Specifically, I have put together a differential I²C (DI²C) setup with the PCA9615 to talk to a string of Bosch IMUs. Behold: an IMU Noodle is born! Grab yourself a cup of coffee and join me as I arm you with the nuts and bolts of DI²C so that you too can run I²C over long cables like a boss.

What’s so Schnazzy about Differential Signals?

There’s a host of ways to make I²C’s communication lines more noise resistant. From all of the choices we covered, I picked differential signals. They’re simple, fairly standardized, and just too elegant to ignore. Let’s take a moment for a brief “differential-signals-101” lecture. Hopefully, you’re already caffeinated! Continue reading “An Introduction To Differential I²C” →

Linux-Fu: Applications On The Web

March 31, 2017 by 38 Comments

Did you know you can run remote Linux GUI programs in a browser with HTML5 support? It’s even secure because you can use SSH tunneling and that little trick means you don’t even need to open additional ports. If this sounds like gibberish, read on, it’s actually pretty easy to get up and running.

I recently was a guest on a Houston-based podcast, and the hosts asked me if the best thing about writing for Hackaday was getting to work with the other Hackaday staff. I told them that was really good, but what I like best was interacting with people (well, most people) in the comments. That sometimes you’d post an article and someone would bring a topic up in comments that would really knock your socks off. This is how I wound up with this nearly ideal remote access solution, that requires nothing on the remote side but a web browser.

A while back I posted about keeping programs running after log off on a Linux box. The post was mostly about non-GUI programs but you could use NX or VNC to handle it. In the comments, someone mentioned how unhappy they’d been with recent copies of NX and another commenter called [Screen for X11] posted about a tool called xpra.

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The $2 32-Bit Arduino (with Debugging)

March 30, 2017 by 120 Comments

I have a bit of a love/hate relationship with the Arduino. But if I had two serious gripes about the original offering it was the 8-bit CPU and the lack of proper debugging support. Now there’s plenty of 32-bit support in the Arduino IDE, so that takes care of the first big issue. Taking care of having a real debugger, though, is a bit trickier. I recently set out to use one of the cheap “blue pill” STM32 ARM boards. These are available for just a few bucks from the usual Chinese sources. I picked mine up for about $6 because I wanted it in a week instead of a month. That’s still pretty inexpensive. The chip has a lot of great debugging features. Can we unlock them? You can, if you have the right approach.

The Part

For a few bucks, you can’t complain about the hardware. The STM32F103C8T6 onboard is a Cortex-M3 processor that runs at 72 MHz. There’s 64K of flash and 20K of RAM. There’s a minimicro-USB that can act as a programming port (but not at first). There’s also many 5 V-tolerant pins, even though this a 3.3 V part.

You can find a lot more information on this wiki. The board is a clone–more or less–of a Maple Mini. In fact, that’s one way you can use these. You can use the serial or ST-Link port to program the Maple bootloader (all open source) and use it like a Maple. That is, you can program it via the USB cable.

From my point of view, though, I don’t want to try to debugging over the serial port and if I have the ST-Link port already set up, I don’t care about a bootloader. You can get hardware that acts as a USB to ST-Link device inexpensively, but I happen to have an STM32VLDISCOVER board hanging around. Most of the STM32 demo boards have an ST-Link programmer onboard that is made to use without the original target hardware. On some of the older boards, you had to cut traces, but most of the new ones just have two jumpers you remove when you want to use the programmer to drive another device.

The “blue pill” designation is just a common nickname referring to the Matrix, not the pharmaceuticals you see on TV ads. The board has four pins at one edge to accommodate the ST-Link interface. The pin ordering didn’t match up with the four pins on the STM32VLDISCOVER, so you can’t just use a straight four-pin cable. You also need to bring power over to the board since it will have to power the programmer, too. I took the power from the STM32VLDISCOVER board (which is getting its power from USB) and jumpered it to my breadboard since that was handy.

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Linux-Fu: Keeping Things Running

March 10, 2017 by 42 Comments

If you’ve used Linux from the early days (or, like me, started with Unix), you didn’t have to learn as much right away and as things have become more complex, you can kind of pick things up as you go. If you are only starting with Linux because you are using a Raspberry Pi, became unhappy with XP being orphaned, or you are running a cloud server for your latest Skynet-like IoT project, it can be daunting to pick it all up in one place.

Recently my son asked me how do you make something run on a Linux box even after you log off. I thought that was a pretty good question and not necessarily a simple answer, depending on what you want to accomplish.

There’s really four different cases I could think of:

  1. You want to launch something you know will take a long time.
  2. You run something, realize it is going to take a long time, and want to log off without stopping it.
  3. You want to write a script or other kind of program that detaches itself and keeps running (known as a daemon).
  4. You want some program to run all the time, even if you didn’t log in after a reboot.

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