This week, as we jump from 2014 into 2015, I’d like to start on an exploration which is dear and near to me: ultra low-power wireless sensor nodes for use in and around the house.

The LPC810 µC has 4 free I/O pins, when connected via a serial port or I2C. And as it so happens, it’s also quite feasible to drive an RFM69 wireless module with just 4 pins, i.e. using just an SPI bus connection, without any interrupt pins hooked up.

So why not try to combine the two, eh?

The following articles introduce a brand new “RF69” driver, using native packet mode:

• Radio blips from an LPC810 – Now
• From RFM69 to RasPi via I2C – Thu

This concludes this year’s refreshed weblog series, but I’m really looking forward to the year ahead. The new weekly format is working out nicely for me – I hope you also like it.

To close off the year and fulfil another goal I had set for myself, the recent material on this weblog has now been added to the The Jee Book. It’s just a start to let you download the entire set of articles published so far – in a range of e-book formats, including PDF.

I hope you had a great 2014 and wish you a very Guten Rutsch into 2015. May it bring you and yours much happiness, creativity, and inspiration – with respect and tolerance for all.

Happy hacking,
Jean-Claude Wippler

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Physical computing is about hooking things up. Sure, there’s also low-power and wireless in the mix, but in the end you need to tie into the real world, and that means connecting sensors, indicators, actuators, and what-have-you-not. It’s a big varied world out there!

The computing side is all about information. From a µC’s perspective, we need to direct information from sensors to us, and from us back out to indicators and actuators.

The more data you need to shuttle across (or the more frequently), the harder it becomes in terms of engineering. But sometimes all you need is to send or receive a few bytes of data, perhaps just a few times per second. That’s where I2C comes in, created over 30 years ago.

Or, more accurately: the I²C bus, which stands for the “Inter-Integrated Circuit” bus.

So the upcoming article series is about this wickedly clever “eye squared see” invention:

• Let’s take the bus – Now
• Masters and slaves – Thu
• I2C on the Raspberry Pi – Fri
• Re-flashing an LPC810 on the RPi – Sat

As before, one article per day. And while we’re at it, I’ll also use the Raspberry Pi single-board computer as an example of how to use I2C under Linux. As you’ll see, it’s really easy!

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The past several weeks were about hacking stuff together: electrically connecting chips and some other components together, and making the resulting circuit + software do fun stuff.

This week is about turning an experiment into a more formal design.

In some cases, such as the mains distribution panel at JeeLabs, clear wiring is not a luxury:

Those colour codes are not for making a pretty picture – the are required by law. And even though most mains distribution panels end up being unique one-offs, the formal “notation” is essential to make each design well-documented and understandable for decades to come.

With low-power experiments, we have a lot more freedom to just hack around, fortunately!

But although breadboards are great for trying out ideas by letting you “edit” the electronic circuit, at some point you will probably want to make it more permanent, or smaller, or more robust – or even all those at once. Or perhaps you simply want to make it repeatable, so more “instances” of your experiment can be produced – whether for fun or for profit, and perhaps even not for yourself but for others to replicate with minimal effort.

Tinkering is fun. Repeatedly solving the same puzzle or falling into the same trap is not.

Here are this week’s articles, as planned for the coming days at 0:00 CET:

• Circuits and schematics – Now
• The magic of copper and solder – Thu
• Laying out and routing a PCB – Fri

Please note that these articles are not a how-to guide for the entire process, just a first introduction to all the steps involved in going from an idea to a reproducible design.

Getting to know the ARM architecture and the LPC810 is a wonderful adventure. It’s also almost impossible to figure out where to start. So let’s just dip our toes in the water, eh?

This week’s articles all highlight a different aspect of the LPC810 (of the entire LPC8xx series, in fact), by exploring a variety of uses and figuring out how to implement them.

Each of the following examples includes a minimal circuit to demonstrate their use:

• Serial output from a DIP – Now
• Number crunching on a DIP – Thu
• Atomic clock via a DIP – Fri
• LEDs racing around a DIP – Sat
• Motion out of a DIP – Sun

All of them can also be built on a breadboard, but soldering up a little circuit with an 8-DIP chip (or socket) in them is a lot more fun. It really shows the versatility of such little µC’s:

Who knows, you might even have an immediate use for some of these examples. With a bit of extra work, any of them could be turned into a self-contained I2C slave to add to your own project. Instead of complicating your own project code with the hard timing requirements of pulsed LEDs or servos, why not simply “off-load” to a dedicated LPC810?

The sky is the limit. Eh, wait, strike that, it isn’t anymore…

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This next article series is about setting up a practical project for use around the house. It’s small enough to be covered in a few articles, and simple enough to be constructed entirely on a breadboard with no soldering involved. It’s time to start making things!

I’ll take you through the problem definition, the way to pick a solution, and the many trade-offs involved in getting everything working as intended. As you will see, getting this thing to run off batteries poses some challenges, but is nevertheless feasible.

Here are this week’s articles, as planned for the coming days at 0:00 CET:

• Let’s build a GPA – Now
• Hardware design choices – Thu
• Measuring distances – Fri
• Reducing power consumption – Sat
• Squeezing a bit more – Sun
• In-System Programming – Mon

The GPA has all the properties you’d expect in a physical computing project: a sensor, a readout, a microcontroller, and a power source. You may not have a garage (or a car), or you may have a car with this functionality built-in, but there’s probably something to glean from this design process for your own use – and maybe some parts will be useful in other ways. It’s all “loosely coupled” after all, with a breadboard to build any variations you like:

Speaking of parts – Martyn & Co have produced a kit for the JeeLabs shop if you’d like to get going fast, with everything needed to create this little parking aid gimmick.

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