Category: programming

Podcasts and Mailing Lists

Posted by Kristian Golding on September 10, 2023

Mailing Lists

Pointer
A reading club For software developers. A newsletter about what current and future CTOs are reading and thinking about.

Podcasts

The Skeptics Guide to the Universe
Weekly science podcast produced by the SGU Productions llc. Also provides blogs, forums, videos and resources.
Coder Radio
A weekly talk show
Oxide Computer Company
Recordings of our weekly live show where we discuss a wide range of topics.
The Changelog podcast
Software's best weekly news brief, deep technical interviews & talk show.
Making Sense Podcast with Sam Harris | Stream Episodes Now
Join Sam Harris for the Making Sense podcast as he debates questions of atheism, politics, self, religion, free will, philosophy, economics, science & more – listen now!
The Great Simplification with Nate Hagens
The Great Simplification with Nate Hagens explores money, energy, economy, and the environment with world experts and leaders to understand how everything fits together, and where we go from here.
About SE-Radio : Software Engineering Radio
Software Engineering Radio is a podcast targeted at the professional software developer. The goal is to be a lasting educational resource, not a newscast. Now a weekly show, we talk to experts from throughout the software engineering world about the full range of topics that matter to professional d…
Programming Throwdown
Episode 163 – Recursion

ESP8266 RGB controller

Posted by Kristian Golding on July 14, 2020

I had a sizable pile of infra-red RGB controllers that came with every RGB LED strip I’ve ever purchased. Still, one was never around when I needed it, and the transmission range was so small that I’d have to move closer to the LED strip to change the color anyway. Finally, there were really only a few unique colors – most looked the same as the next. I decided to instead replace the RGB LED PWM generator with an ESP8266 (as a NodeMCU) that I could control via a web interface from my phone.

For the code I found this excellent resource: https://tttapa.github.io/ESP8266/, in particular, I took the Chapter 14 example and made some updates to support the LittleFS file system (the only change that’s absolutely required is the SSID and password for your WiFi access point): https://github.com/daecks/ESP8266/tree/master/Examples/14.%20WebSocket/A-WebSocket_LED_control

Given that I had a couple of RGB signal boosters, I did not need to use high-current MOSFET transistors to drive my 15-foot LED strips, and instead I chose to use 2N2222 NPN transistors because I have an ample amount of them. The RGB LEDs in the strips are SMD 5050s, which are rated at 60 mA per LED channel. The strips come with their own resistors, so all that’s needed is to drive the NPN transistor with the correct base current.

To have the transistor act as a PWM switch, the recommendation is to have the collector-emitter current be 15-times that of the base current, meaning my base current would be (current per LED / 15) = (60 / 15) = 4 mA, which the ESP8266 can handle (the limit is 12 mA per pin). The voltage output of a ESP8266 GPIO pin is 3.3 volts, and the voltage drop across the transistor is ~ 0.7 volts, so given this and Ohms law, I could determine the base resistor to use: V = IR, R = V/I, R = (ESP8266 voltage – transistor drop)/ 4mA = (3.3 – 0.7/ 0.004) = 650 Ohms. The closest resistance value to this is 680 Ohms, so I went with that.

Schematic for circuit
Breadboard layout
The final result
The web interface for controlling the color

References

A journey with “Embedded programming with Android”: part 1

Posted by Kristian Golding on November 13, 2019

I purchased the Kindle edition of this book: https://www.amazon.com/Embedded-Programming-Android-Bringing-Scratch-ebook/dp/B013IQGX3A

and since I’m going through the book in 2019, there are a few gaps to bridge.   The first was creating an emulator.  I did this via command line, and step 1 was to get a basic Android SDK downloaded.  I use Vagrant/Virtualbox for my development, so this was used to set up the SDK

put this here

Once that’s done, I need to configure my emulator to use Android API 15.  To get an idea of what I can install, I use the sdkmanager tool to list all the available options:

$ANDROID_HOME/tools/bin/sdkmanager --list

Which gives a bunch of output, but I’m only interested in the android-15 results:

  system-images;android-15;default;armeabi-v7a      | 5    | ARM EABI v7a System Image
  system-images;android-15;default;x86              | 5    | Intel x86 Atom System Image
  system-images;android-15;google_apis;armeabi-v7a  | 6    | Google APIs ARM EABI v7a System Image
  system-images;android-15;google_apis;x86          | 6    | Google APIs Intel x86 Atom System Image

The book says we’ll be developing for arm, and I don’t think I’ll need Google APIs, so Ihoose the armeabi-v7a.  I don’t know how this is all going to fly in Virtualbox either, so I yolo by running the following command and accepting license with “y”.

$ANDROID_HOME/tools/bin/sdkmanager "system-images;android-15;default;armeabi-v7a"

Cool.   Now to create an emulator image, right?  I don’t have any idea of how to configure it via command line, but I’ll try and feel my way through:

$ANDROID_HOME/tools/bin/avdmanager create avd --name mytestavd --abi default/armeabi-v7a --package "system-images;android-15;default;armeabi-v7a"

Which results in “Error: “emulator” package must be installed!”

Ok, let’s install that (and wait!):

$ANDROID_HOME/tools/bin/sdkmanager emulator

And then I try re-running the command to create the avd, this time successfully.  I answer “no” to creating a custom hardware profile, as I answered “yes” the first time and didn’t know what to answer for some of the questions.  I believe I can play around with this at a later time.  Now where did that go?   Find out with this command:

 $ANDROID_HOME/tools/bin/avdmanager list avd

Output:
Available Android Virtual Devices:
    Name: mytestavd
    Path: /home/vagrant/.android/avd/mytestavd.avd
  Target:
          Based on: Android 4.0.3 (IceCreamSandwich) Tag/ABI: default/armeabi-v7a

So, it seems like we may have some basic steps done.  More will be done in a part 2 of this post, hopefully in the New Year.

Docker image to run a quick PHP test server

Posted by Kristian Golding on August 5, 2018

I had a need to run a PHP-capable web server on my Vagrant box to locally test some Javascript that queried a database via PHP, and then presented that via Google Charts.  This Docker image suited that use case just fine.  Replace <full path to location you want as root> as appropriate:

sudo docker run --name web-server -p 127.0.0.1:80:80 -v /opt/mysql:/var/lib/mysql -v <full path to location you want as root>:/web -d osws/php-web-server