my recent reads..

LEAP#173 Mini 64-LED Cube

LED cubes were a "thing" a few years back maybe ... but I've never built one. Time to fix that...

Here's my "mini" 4x4x4 cube - 3cm per side with 3mm clear blue LEDs. Pretty compact, and delivers nice effects. The clear blue LEDs work really well - very bright, even when driven with minimal current.

It's encased in a Ferrero Rocher cube box. During the build, that raised some challenges - most of the effort in building the project concerned squeezing all the electronics into the space in the lid (which becomes the base of the cube). Not quite as small as HariFun's "World's Tiniest RGB LED Cube" but about as small as you can get without resorting to SMD LEDs!

As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub. Here's a quick demo:

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LEAP#100 Retrogaming on an Arduino/OLED "console"

(blogarhythm ~ invaders must die - The Prodigy)
Tiny 128x64 monochrome OLED screens are cheap and easy to come by, and quite popular for adding visual display to a microcontroller project.

My first experiments in driving them with raw SPI commands had me feeling distinctly old school, as the last time remember programming a bitmap screen display was probably about 30 years ago!

So while in a retro mood, what better than to attempt an arcade classic? At first I wasn't sure it was going to be possible to make a playable game due to the limited Arduino memory and relative slow screen communication protocol.

But after a few tweaks of the low-level SPI implementation, I was surprised myself at how well it can run. Even had enough clock cycles left to throw in a sound track and effects.

Here's a quick video on YouTube of the latest version. ArdWinVaders! .. in full lo-rez monochrome glory, packed into 14kb and speeding along at 8MHz.

As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.

Full source and schematics are in the LittleArduinoProjects collection on Github.
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LEAP#018 The Fretboard - a multi-project build status monitor

(blogarhythm ~ Diablo - Don't Fret)

The Fretboard is a pretty simple Arduino project that visualizes the build status of up to 24 projects with an addressable LED array. The latest incarnation of the project is housed in an old classical guitar … hence the name ;-)

All the code and design details for The Fretboard are open-source and available at Feel free to fork or borrow any ideas for your own build. If you build anything similar, I'd love to hear about it.

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cancannible role-based access control gets an update for Rails 4

Can You Keep a Secret? / 宇多田ヒカル

cancannible is a gem that has been kicking around in a few large-scale production deployments for years. It still gets loving attention - most recently an official update for Rails 4 (thanks to the push from @zwippie).

And now also some demo sites - one for Rails 3.2.x and another for Rails 4.3.x so that anyone can see it in action.

So what exactly does cancannible do? In a nutshell, it is a gem that extends CanCan with a range of capabilities:

  • permissions inheritance (so that, for example, a User can inherit permissions from Roles and/or Groups)
  • general-purpose access refinements (to automatically enforce multi-tenant or other security restrictions)
  • automatically stores and loads permissions from a database
  • optional caching of abilities (so that they don't need to be recalculated on each web request)
  • export CanCan methods to the model layer (so that permissions can be applied in model methods, and easily set in a test case)

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