This is the beginning of a post from about:benjie. If you’ve written a blog post you think would be useful to SoutHACKton members, please get in touch!

I’m working on a new project, I’ve got a 8×8 dual colour dot matrix display (£2.50 delivered from Earthshine Design) and I want to power it from the Arduino. One way of making a chip like that (which has 2×8×8 = 128 LEDs) would be to have a common ground and an additional 128 pins – one for each LED. This, I think you’d agree, would be a nightmare, so instead they’ve basically gone for an 8×16 grid for a total of 24 pins. This raises two main problems:

1. You can’t turn 2 arbitrary LEDs on at the same time unless they are on the same row/column. (Doing so would actually draw a square of LEDs.)
2. My Arduino doesn’t have enough digital input/output pins

Point 1 is easily solved – we simply update just one row at a time, letting Persistance Of Vision (POV) do the hard work for us. Point 2 is the subject of this post – multiplexing, combining multiple individual signals into just one signal. I will not be using this dot matrix display in this post, instead I will simply be powering normal LEDs. I wanted to find out if the Arduino is fast enough to multiplex the data through just a few pins in order to power this display. The answer (one of my favourite answers!) is: “Yes, but not without some hacking.” Read on…

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Sunday 4th October 2009, 10:30am-6:30pm, Steamshift HQ

As the Arduino meeting was such a success, we’ve already booked our next meetup – a Hack Day – again kindly hosted by Steamshift at their HQ in Eastleigh.

What is a Hack Day?

It’s a day where everyone brings along their current projects (if any) and can work on them in the presence of other like-minded individuals. Just starting out with Arduino? Putting the finishing touches on your latest life-size robot? Planning to build a water jet-pack? Hacking electronics into clothing? Hacking together the components necessary to make a new GNU/Linux distro or media centre software? Join us!

What if I don’t have a current project?

Come along anyway – help with someone else’s! Skilled or unskilled, knowledgeable or not-so-knowledgeable, all are welcome!

Why is it so long?

The idea is that people can turn up when they want for however long they want – pop in for just a couple of hours or come for the whole day – it’s completely up to you! We anticipate that the busiest time will be 12:30 until 4:30.

Why so early? (Also: what about lunch?)

We thought it would be nice to have lunch together (at around 1pm, though the timing is up to the individual) – some of us will probably order pizza, others may bring lunch with them. However, we didn’t want to cut into two meal times so we’ve aimed for “after breakfast and before dinner.” Everyone is responsible for bringing/ordering their own food and drink.

Where do I sign up?

This will be another free (no cost) day, all you need to do is turn up. We like to know how many people are coming though, so please join the Google Group and drop a short message in this thread.

Looking forward to seeing you there!

This event is kindly hosted by Steamshift.

Steamshift develops creative solutions to technical challenges primarily in the fields of web application development, flash AS3 programming and linux hosting. They work closely with their design and branding partners to deliver an end-to-end solution.

Saturday 29th August 2009, 2pm, Steamshift HQ

Steamshift have kindly offered to host our next meeting which is targetted at introducing us to the Arduino and similar development boards.

No prior knowledge is necessary, but if you already have an Arduino/Freeduino/PICAXE/etc board, please feel free to bring it along, and if you like you can even teach the rest of us about it. Andy from Steamshift will be bringing a number with him, and there are a number of people on the groups who will be bringing theirs too.

I don’t feel knowledgeable enough to tell you much about Arduino, so instead, I suggest you go to Wikipedia, or the Arduino website:

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It’s intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.

Arduino can sense the environment by receiving input from a variety of sensors and can affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is programmed using the Arduino programming language (based on Wiring) and the Arduino development environment (based on Processing). Arduino projects can be stand-alone or they can communicate with software on running on a computer (e.g. Flash, Processing, MaxMSP).

The boards can be built by hand or purchased preassembled; the software can be downloaded for free. The hardware reference designs (CAD files) are available under an open-source license, you are free to adapt them to your needs.

Arduino received an Honory Mention in the Digital Communities section of the 2006 Ars Electronica Prix.

Please, if you have any friends who you think might be interested, spread the word! Arduino is a very flexible platform and can be used for hardware hacking, home automation, robotics, and millions of other things.

Bring as much of the following as you can (all are totally OPTIONAL):

• Laptop with a free USB port
• Arduino/Freeduino/PICAXE/etc boards (I suggest marking them in some way so they don’t get mixed up!)
• Components: breadboards, LEDs, resistors, capacitors, Arduino shields, light dependant resistors, proximity sensors, speakers, buzzers, switches, …
• Cash (in case a quick trip to Maplin might be required, or in case you want to buy an Arduino board/some components off of someone else)
• Camera/camcorder to document the day!

If you can make it, please let us know in the group or by commenting on this post so we know how many people to expect.

My thanks go out again to the guys at Steamshift, especially Andy, for making this next meetup possible: