Category Archives: ARM

Posts relating to ARM embedded work

Introducing the Tiny Home Area Network Stack

TinyHAN MQTTIn the past I have bemoaned the resource requirements and closed nature of “standard” RF protocols such as ZigBee and other 802.15.4 based specs.  In the meantime low-cost radio modules like the RFM12B, RFM22B and the newer RFM69 series (all from HopeRF) have started to become the radios of choice in open source Internet of Things projects.  The problem is that despite a tendency towards standards like MQTT and HTTP on the Internet side, there does not seem to have been any attempt to standardise on what goes over the air, leaving a situation where everyone uses the same radios but nothing can actually interoperate.

Tiny Home Area Network (TinyHAN) is an attempt to address this in the form of an Apache licensed, highly portable protocol suite for resource constrained embedded systems using cheap sub-GHz radio hardware.  The software is written in portable C and uses a layered approach to enable interoperability even between devices using different radios.  This initial release of the suite supports basic client/server topologies currently without security, but with authentication and encryption to be added in the near future.  Various examples are included, as well as a GnuRadio based sniffing tool that can be used with an RTL-SDR dongle.

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WG2 Flight Update

ms_wg2_final_smallThe WG2 long-range balloon flight is now over as far as being able to track it is concerned; it is quite likely still in the air somewhere over Russia, however (as of 27/6/14).

The flight performed much better than we expected for a first try, covering a known distance of 1500 miles, to finally go out of ground-station range over Ukraine about 31 hours after launch.  During the flight the balloon passed through a total of 8 countries (some more than once).

The balloon’s telemetry signal was received across Europe by a network of volunteers (many of whom are amateur radio operators), and fed into the central Habitat system operated by the UK High Altitude Society (UKHAS).  This enabled the flight to be seen in real-time through the site.

At the time contact was lost the balloon and the tracking electronics remained in good health, with the battery expected to last perhaps a further 8 to 10 hours.  Long-range flight predictions from the last known point suggest that the balloon will, if it remains airborne, travel up into Russia and then continue East towards Siberia.

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Tiny Balloon Tracker

Tiny balloon trackerToday sees the first flight of my tiny ARM based GPS tracker.  The balloon (a 36″ Qualatex foil) was launched from Wirral Grammar School for Girls with their Astronomy Club, who were responsible for the successful WGGS1 high-altitude launch last October.

This flight is a float attempt, and can be tracked at with the callsign WG2.  Calculations suggest the battery (a single AAA) should be good until about Friday morning.

The tracker, shown in the picture (more here), has the connector piece removed once programmed.  For scale, the board is the same length as the AAA that powers it.  Wire antennas were used for both GPS and downlink, and these were just soldered straight to the board.  Total mass is about 12 g including the battery.  Technical details of the tracker follow…

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