Computing stuff tied to the physical world

Archive for May 2015

RFM69 on ATmega

In Book on May 27, 2015 at 00:01

Now that we have the RFM69 working on Raspberry Pi and Odroid C1, we’ve got all the pieces to create a Wireless Sensor Network for home monitoring, automation, IoT, etc.

But I absolutely don’t want to leave the current range of JeeNodes behind. Moving to newer hardware should not be about making existing hardware obsolete, in my book!


The JeeNode v6 with its on-board RFM12 wireless radio module, Arduino and IDE compatibility, JeePorts, and ultra-low power consumption has been serving me well for many years, and continues to do so – with some two dozen nodes installed here at JeeLabs, each monitoring power consumption, house temperatures, room occupancy, and more. It has spawned numerous other products and DIY installations, and the open-source JeeLib library code has opened up the world of low-cost wireless signalling for many years. There are many thousands of JeeNodes out there by now.

There’s no point breaking what works. The world wastes enough technology as it is.

Which is why, long ago a special RF69-based “compatibility mode” driver was added to JeeLib, allowing the newer RFM69 modules to interoperate with the older RFM12B’s. All you have to do, is to add the following line of code to your Arduino Sketches:

#define RF69_COMPAT 1

… and the RFM69 will automagically behave like a (less featureful) RFM12.

This week is about doing the same, but in reverse: adapting JeeLib’s existing RF12 driver, which uses a specific packet format, to make an RFM12 work as if it were an RFM69:

As I’ve said, I really don’t like to break what works well. These articles will show you that there is no need. You can continue to use the RFM12 modules, and you can mix them with RFM69 modules. You can continue to use and add Arduino-compatible JeeNodes, etc. in your setup, without limiting your options to explore some of the new ARM-based designs.

Let me be clear: there are incompatibilites, and they do matter at times. Some flashy new features will not be available on older hardware. I don’t plan to implement everything on every combination, in fact I’ve been focusing more and more on ARM µC’s with RFM69 wireless, and will most likely continue to do so, simply to manage my limited time.

Long live forward compatibility, i.e. letting old hardware inter-operate with the new…

RFM69 on Raspberry Pi

In Book on May 20, 2015 at 00:01

With the Micro Power Snitch sending out packets, it’d be nice to be able to receive them!

This week is about turning a Raspberry Pi, or a similar board such as an Odroid-C1, into a Linux-based central node for what could become a home-based Wireless Sensor Network.

All it takes is an RFM69 radio module and a little soldering:

DSC 5086

On the menu for this week’s episode:

And before you know it, you’ll be smack in the middle of this century’s IoT craze…

(For comments, visit the forum area)

Micro Power Snitch, success!

In Book on May 13, 2015 at 00:01

We’ve come to the eighth and final episode of the Micro Power Snitch story: it’s working! The circuit is transmitting wireless packets through the RFM69 radio module running on nothing but harvested electromagnetic energy. Install once, run forever!

But there are still several little details, optimisations, and edge cases we need to take care of – which is what this week’s articles are all about. As always, one article per day:

The MPS triggers on any appliance drawing ≥ 500W (on 230 VAC, or 250W for 115 VAC):

DSC 5089

As always on the JeeLabs weblog: everything is open source – you are welcome to build and adapt this circuit for your own purposes. If you do, please consider sharing your suggestions/findings/improvements on the forum, for others to learn and benefit as well.

(For comments, visit the forum area)

Micro Power Snitch, part 7

In Book on May 6, 2015 at 00:01

The two problems with projects powered by harvested energy, are: 1) running out of juice, and 2) falling into a state of limbo and not (or not consistently) getting out of it again.

Here is an example of both happening – a successful µC startup and then a radio failure:


In the case of the Micro Power Snitch, the energy coming in may vary greatly, since it will be proportional to the current drawn by the appliance being monitored by our MPS.

We’re going to have to tread carefully in this week’s episode:

As usual, each of the above articles will be ready on successive days.

Planned for next week: a few more loose ends, and then my closing notes.

(For comments, visit the forum area)