Microcontroller Solutions TechZone Magazine, April 2011 - Digikey

Deeply Embedded Devices:
The “Internet of Things”
by Mark Wright and Rodger Richey, Microchip Technology Inc.
The “Internet of Things” consists of
interconnected, deeply embedded devices
that need to communicate while maintaining
extremely long battery life. Fortunately there
are some low-power RF solutions that address
both halves of the problem.
The “Internet of Things” is about connecting products that create,
store, and consume data via the Internet. This allows processing to
provide results that can be more easily used by people. The basic
technical requirements to enable this are vastly different from the
current treadmill of mainstream Internet-connectivity technology.
Mainstream connectivity strives to constantly increase bandwidth,
range and features to counter dwindling margins and prepare for
the next “killer” application. Whether this is HD media serving,
on-demand TV, 4-play (voice, data, Internet and multimedia), Network
Attached Storage (NAS), or the next thing you absolutely must have,
mainstream connectivity requires a wider, faster-pipe mentality.
Mainstream provisioning, however, is fundamentally disjointed from
the requirements of the “Internet of Things.” While an Internet gamer
will pay $150 to replace his 802.11b/g access point with the latest
802.11a/b/g/n access point, in order to reduce game “latency” or
increase their virtual “survivability,” this is not a price option for
adding connectivity to a thermostat, temperature sensor, garagedoor
opener, coffee maker, or lawn sprinkler. In short, the “Internet
of Things” dictates a signifi cantly different adoption model than
mainstream broadband support.
Applications can be categorized as open, embedded, and deeply
embedded. Open systems are compute-based products with
purpose-loaded functions. Open systems may change their nature
from one use to another. A laptop that is confi gured to be a word
processor in one setting and an Internet-connected media player
in another is an example of this. Due to the varying uses of open
systems, the capabilities must be fl exible yet high-performance
in nature, with the limitations usually driven by cost. Embedded
systems are fi xed function. They may be very high- or lowperformance,
with a limited energy footprint. Deeply embedded
systems are single-purpose devices that are used to detect
something in the environment, perform a basic level of processing
and then do something with the results.
Table 1: Comparison of device categories.
Categories Product Examples Battery Life Data Rate Range
Open PC 4 - 8 hours High Max.
Embedded Access Point, iReader, AC Powered or
Pocket Dictionary up to 2 years
High 30 m - Max.
Deeply
Embedded
Sprinkler Valve, Locks,
Power Monitor
The “Internet of Things” is primarily driven by deeply embedded
devices. These devices are low- bandwidth, low-repetition
data capture, and low-bandwidth data usage “appliances” that
communicate with each other and provide data via user interfaces.
There are embedded appliances, such as high-resolution video
security cameras, video VOIP phones, and a handful of others that
require high-bandwidth streaming capabilities. This article instead
targets the countless products that simply require packets of data to
be intermittently delivered.
Figure 1: Device categories.
2 years + Low - Med. 30 m
Data-rate requirements and the corresponding power consumption
vary signifi cantly between the different device categories. Open-type
devices utilize Pentium class or similar processing, and run complex
OS-based protocols for communication. Such devices require mains
power, or utilize large batteries and have battery life measured in
hours. Battery-operated embedded devices are products for which
it is critical to reduce power consumption, design complexity, and
cost through the optimization of computation occurring in the device.
This is done through the use of specialized hardware, or less fl exible
purpose-driven software. Deeply embedded devices build upon
this optimization and often require battery operation, which creates
a critical need for low power consumption. These products utilize
low-power microcontrollers such as the 16-bit PIC24F family from
Microchip, which features low-power sleep currents down to 20 nA
and allows the use of AA or coin-cell batteries for up to 20 years of
operational life.
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