Howto: Arduino Pin Speed (Multiplexing)

Posted on September 8, 2009 by Benjie

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:

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.)
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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Hack Day 1 – Meetup

Posted on September 3, 2009 by Benjie

: Image via Wikipedia

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.

Review of the Arduino meet

Posted on September 1, 2009 by Jem

Our next meeting, Hack Day 1, is on 4th October. Click here for details.

At 2pm Saturday 29th of August, on an otherwise uneventful bank holiday weekend, a varied group of men and women met at Steamshift HQ. Their purpose – to get down to business and HACK! Some arrived with projects in mind – disco lights, energy usage monitoring, laser mazes – while others turned up with little equipment but an eagerness to get their hands dirty. At the full height of the meet, there were around twenty people there, playing around with Arduino and PIXACE boards.

Southackton Meet

The meet was organised and hosted by Andy Bennett and Steamshift as part of SoutHACKton – a group of like-minded Solent residents who all want to kick back, take stuff apart and build new things out of the resulting mess.

And that they did – sometimes clusterd in small groups, working away on personal projects, sometimes coming together in larger groups to admire a piece of someone else’s handy work. Projects that drew particular attention were Ruzz’s walking robots (a hit at our last meet too), Andy T‘s LEDs (Did I mention he has 4,000 LEDs?) and my own project: Lou Lou the Furby. I hope to hook Lou Lou up to the PC and tell me when I get new email. Maybe she’ll get her own twitter account one day. For now, she’ll just have to be happy playing sounds from my eeePC through an Arduino.