the wireless quarter - Nordic Semiconductor

Transcription

the wireless quarter - Nordic Semiconductor
QUARTER 4 2007
www.nordicsemi.com
THE WIRELESS QUARTER
In this issue
NEW PRODUCT
nRF24LU1 redefines benchmark for
USB wireless peripherals
}
u Avoiding interference
on the 2.4GHz desktop
p Will ULP Bluetooth
make it in healthcare?
u ULP Bluetooth and
ZigBee compared
p People & faces
nRF24LU1 produces dime-sized USB dongles
emulate non-volatile memory.
The latter removes the need for an
external EEPROM.
A full suite of development tools
has been launched alongside the
nRF24LU1 to allow accelerated,
low risk and cost effective adoption
of the chip. The suite includes
a production-ready USB dongle
Reference Design, Software
Development Kit and complete
Hardware Development Kit.
In operation, the nRF24LU1 is a
true single chip wireless solution
for USB dongles that requires no
external voltage regulator as it
can be powered directly from the
USB bus using an internal voltage
regulator. The 5 by 5mm chip also
generates all necessary clocks from
a single 16MHz external crystal (so
doesn’t need the additional crystal
typical of two-chip approaches).
The performance of a USB
dongle for wireless peripherals is
primarily affected by three factors:
The data transfer rate between
the PC and USB dongle, the
microcontroller employed within
the dongle itself for simultaneous
data processing, and the on-air data
communication rate of the 2.4GHz
transceiver used. The nRF24LU1
uniquely delivers a full-speed USB
12Mbps PC to USB transfer rate,
a powerful and highly optimised
embedded 8051 microcontroller,
plus a 2Mbps air data rate.
Credit card-sized RF keypads yield 90-percent pass rate
A leading US-based provider of
audience response systems – Turning
Technologies, LLC – has standardised
on Nordic Semiconductor 2.4GHz
transceivers in its TurningPoint® software
and credit card-sized RF ResponseCard®
wireless keypads.
The keypads, developed by Turning
Technologies’ hardware division
Responsive Innovations, enable
Microsoft® PowerPoint® presentations to
become completely interactive including
real-time feedback and assessments.
In the education market, US case
studies show failure rates in
traditionally hard-to-teach
subjects such as algebra can
fall by up to 90 percent when
this technology is employed
in the classroom.
Nordic transceivers
are used in the new
XR ResponseCard
(nRF24L01)
with LCD screen and the existing RF
ResponseCard (nRF24E1). The latter
has an installed base of over a
million units.
By allowing audiences
and students to participate
in presentations or lectures,
a TurningPoint audience
response system makes
them significantly more
engaging, interactive and
measurable.
WELCOME TO THE WIRELESS QUARTER
This is the 6th issue of Nordic’s quarterly newsletter. It is designed to keep you updated on the latest news and
developments at Nordic and is supplied free-of-charge.
PLEASE FORWARD THIS NEWSLETTER TO ANY COLLEAGUES OR CUSTOMERS WHO MAY FIND IT USEFUL
To subscribe (or un-subscribe) please e-mail: [email protected]
NORDIC MARCH 2006 1
The Bluetooth™ word mark and logo are registered trademarks and are owned by the Bluetooth SIG
p Building practical
wireless networks
The launch of Nordic’s brand
new nRF24LU1, 2.4GHz single
chip transceiver instantly redefines
the industry benchmark for size,
performance and security of USB
dongles for ultra-low power wireless
peripherals.
The nRF24LU1 enables the
development of ultra-compact
USB dongles with a unique
combination of future-proofed
performance and security. This
includes native support for up
to five bidirectional ultra-low
power wireless peripherals
communicating simultaneously
via a single, full-speed USB 2.0compliant miniaturised dongle.
Full interoperability with
Nordic’s existing nRF24L01
– including its unique Enhanced
ShockBurst™ hardware link layer
– is also included, plus an 8051
compatible microcontroller,
hardware AES security co-processor
and 16kbytes of internal Flash
memory that can be used to
www.nordicsemi.com
ANT UPDATE
“With Nordic’s RF
Silicon Solutions,
designers can build
cost effective wireless
connectivity into
their products more
quickly”
Thomas Embla Bonnerud
Dear Reader,
This is the last issue of The Wireless Quarter for 2007. It does seem
incredible that the year is already ending. For all of us at Nordic, 2007
represents a year where the company has taken giant leaps forward
to become the leader in our chosen sector of ultra-low power wireless
connectivity. While much of our success is based on the PC peripherals
sector, we have seen the business expand into several other major
consumer areas.
As reported in The Wireless Quarter during the year, Nordic has had
design wins with the nRF24xxx family in sectors as diverse as sports,
audio, medical, networking, VoIP and industrial among others. Hardly
a week goes by without the announcement of another success on the
news section of our website at www.nordicsemi.com. These successes
from around the globe have enabled Nordic to reinforce its position as the
leading solution provider for ultra-low power wireless connectivity. On top
of that, we have found time to take a major role in the development of the
Wibree open industry wireless initiative (now part of the ultra low power
– or ULP – Bluetooth specification).
But we’re not about to rest on our previous successes as we look
forward to 2008. Nordic’s R&D team is busier than ever developing the
2.4GHz silicon and software that will continue to set new standards in
ultra-low power consumption and price/performance ratio for wireless
connectivity. We’ve listened to customer feedback and are working to
ensure that Nordic offers complete RF Silicon Solutions.
Nordic has always been much more than a silicon supplier. The
company’s staff has consistently worked with individual customers to
ensure their applications perform perfectly. But now we have formalised
this approach by offering complete RF Silicon Solutions for every
new product. RF Silicon Solutions comprise RF silicon (standalone or
embedded transceivers), proprietary software stacks (application specific
or used for reference designs), reference designs (which can even be used
as production-ready products), and development tools (development kits,
PC-based software for development kits, software development kits for
embedded radios and production test kits).
With these RF Silicon Solutions for each new product, customers will be
able to develop innovative products with wireless connectivity in less time
and at less expense.
At Nordic we’re looking forward to the new year and to working closely
with existing and new customers, not least because it’s fun to see the new
ways they find to exploit our wireless technology in their latest products.
Yours Sincerely,
Thomas Embla Bonnerud
Product Manager Standard Components
2 NORDIC WIRELESS QUARTER Q4 2007
ANT demonstrates its advantages
over ZigBee
By Brian Macdonald, Director - ANT
}
Recently, Nordic’s nRF24AP1 plus ANTTM with SensRcoreTM was
compared with a ZigBee system from a well-known manufacturer.
Conducted by independent engineering organization Au-Zone
Technologies (www.au-zone.com), the comparison test implemented a
simple wireless security system using modules from each company.
While the developers were experienced in embedded product design
and wireless technologies they had no specific prior experience with
either the nRF24AP1 plus ANT or ZigBee, making the trial unbiased.
Standard vendor supplied modules from their respective
development kits were employed. The specific areas of comparison were:
· The out-of-box experience for the developer;
· The effort level of developing the application with standard modules;
· The quality, accuracy and comprehensiveness of documentation;
· The performance of firmware drivers, API’s and sample code;
· The performance of the demo systems once implemented;
· The cost and size of the wireless sensor modules.
At Nordic Semiconductor and ANT, we know that ZigBee’s relatively
complex protocol and nodes of varying functionality make setting
up even a simple network difficult and time consuming. And that’s
without considering the issues of size, cost and power consumption.
In comparison, Nordic Semiconductor and ANT’s technology is
intentionally engineered to simplify practical wireless network
development and optimise network operational efficiency. But would
these advantages come to the fore in Au-Zone’s unbiased test?
We needn’t have worried. Au-Zone’s test exposed the deficiencies of
ZigBee while underlining the nRF24AP1 plus ANT with SensRcore’s key
advantages of simplicity, small size and ultra-low power consumption.
When it came to setting up the security network ZigBee took twice as
long to configure as Nordic and ANT’s technology (at 160.5 hrs compared
to 83 hrs). And even then, Au-Zone considered the ZigBee application as
a “work in progress, [with] some outstanding issues to be addressed”.
Au-Zone continued by saying: “Overall the ANT PC application
[SensRcore development platform] was a much more pleasant
experience. Once the network configuration was understood, the
developer was able to concentrate specifically on the application
development and not worry about the underlying ANT protocol.”
In addition, Au-Zone said that Nordic and ANT’s technology offered
“significant advantages over ZigBee for short range wireless sensor
implementations requiring low power operation”. Au-Zone concluded:
· The quality of the Nordic and ANT module, firmware support and
documentation enabled the implementation of a more robust system
with half the development effort;
· The Nordic and ANT module require only 60 percent of the area of the
ZigBee module with an equivalent antenna implementation;
· The Nordic and ANT module requires significantly less power
permitting higher data sensor rates using small coin cell batteries.
While we’re confident of the advantages of our product, it’s good to
have some occasional independent backing.
NEWS
COMPUTER PERIPHERALS
IN BRIEF
Kensington slims down computer
peripherals integration
}
Kensington® has managed
to combine many previously
standalone computer input devices
into one for mobile users. Yet the
Kensington SlimBlade Lifestyle
Collection, which includes five
products that communicate using
Nordic’s ultra-low power nRF24L01
2.4GHz transceivers, still combines
ultra thin design with multiple
layers of functionality in a robust
set of devices designed to work in
any environment.
The SlimBlade Presenter Media
Mouse, for example, offers the 3in-1 functionality of a previously
separate wireless mouse, presenter
and RF controller product, yet is
25-35 percent thinner than most
standard notebook mice. Further,
it communicates like most of the
SlimBlade Collection via a microsized USB wireless receiver about
one third smaller than traditional
USB wireless receivers, small
enough to be stored within the
housing of the mouse products
themselves when not in use.
“This level of integration
is a must have for the techsavvy mobile professional
Kensington is targeting with the
SlimBlade Collection,” explains
Wireless home automation
Christine Dumery, Marketing
Communications Director at
Kensington. “Travelling executives
need to get the most out of their
computers in all the terrain
settings that comprise a full mobile
experience – be it an office desk,
an airport seat, a hotel room or
their sofa at home. By combining a
unique feature set with unrivalled
simplicity, each SlimBlade product
is designed to work flawlessly and
intuitively to fit its user’s lifestyle
– there can be no performance
compromises.”
In the Kensington SlimBlade
Lifestyle Collection – that comprises
wireless mice, RF controllers and
presenters plus a magnetically
modular wireless keyboard, keypad,
laser mouse and RF controller
Media Notebook set – this is
achieved by using ultra-low power
Nordic nRF24L01 transceivers
in each input device and the
micro USB receiver (apart from
the SlimBlade Trackball Mouse
that employs Bluetooth wireless
technology but can function
alongside any SlimBlade product).
The ultra-low power
performance of the Nordic
nRF24L01 transceivers allows a
pair of AAA 1.5V cells to power the
wireless link of each SlimBlade
device for up to a year under heavy
usage conditions and provides a
10 m (30-ft) operating range even
when obstructions such as people
or furniture are in the way.
PROTOCOL SOFTWARE
Nordic-developed RF protocol stack gives desktop
control devices best-in-class battery life
}
The Wireless Desktop Protocol
eliminates the need for
engineers to write or source a
protocol when employing Nordic’s
ultra-low power 2.4GHz transceivers
in wireless computer peripherals. It
is available to all Nordic customers
developing projects with any
Nordic 2.4GHz transceiver(s).
This complete, off-the-shelf
RF protocol communication
software stack is designed to
enable robust, high-performance
wireless connectivity for a wide
range of advanced RF control
devices, and includes an Enhanced
ShockBurst™ link layer with all
necessary upper protocol layers. It
is also pre-optimised for ultra-low
power consumption on the device
(controller) side by minimising
the time on air. This enables the
implementation of products with
best-in-class battery lifetimes.
Excellent 2.4GHz co-existence
performance is assured thanks
to an advanced asynchronous
frequency agility transmission
scheme, and unique ReverseBurst™
feature allows simple high-
throughput data streaming
from the host (appliance
being controlled) to the device
(controller), making it a perfect
solution for the bidirectional
communications demanded by
advanced Media Centre remote
controls with displays.
The protocol stack also provides
native support for star topology
networking of up to 5 control
devices with bidirectional data
comms to one host. 3-in-1 desktop
bundles (mouse, keyboard, remote)
are therefore easily developed.
Norwegian domestic heating,
control and automation specialist,
NOBO Heating, has incorporated
Nordic Semiconductor nRF905
433/868/915MHz multiband
transceivers into the heart of its
newly launched and stylish Orion EC
700 wireless home automation and
control system. This allows multi-zone
wireless control and automation
of domestic heating, lighting and
electrical appliances.
Foot warmer is cosy for
winter sports
Austrian winter footwear heating
and drying specialist, Therm-ic, has
specified Nordic nRF24E1 2.4GHz
transceivers into its ThermiControl
wirelessly controlled foot warmers.
These ensure foot temperature is
controlled in winter sport and cold
working environments to prevent
injury and fatigue.
Wireless sensor networking
out of the box
Designers can now build functioning
wireless sensor networks (WSNs)
within minutes using a development
kit from ANT™ with Nordic 2.4GHz
transceivers. The ANTDKT3 WSN
development kit uses Nordic
Semiconductor nRF24AP1 and
nRF24L01 2.4GHz transceivers
running the ANT wireless sensor
network protocol to offer the easiestto-use wireless sensor networking
development kit available.
NORDIC WIRELESS QUARTER Q4 2007 3
www.nordicsemi.com
WIRELESS NETWORKING
Building practical wireless networks
Building a practical wireless network can be a daunting challenge. Nordic’s
nRF24AP1 eases the task
T
he nRF24AP1 combines an ultralow power transceiver for wireless
communications with ANTTM’s
production-proven ultra-low power
wireless sensor networking (WSN) protocol,
to create a single chip networking solution.
The nRF24AP1 is the answer for users who
are looking for an easy-to-implement 2.4GHz
transceiver for global operation, but who
don’t necessarily want to spend months
integrating a networking standard protocol
into their system.
The nRF24AP1 suits almost all practical,
ultra-low power wireless networking
applications – from simple point-to-point
to complex meshes. Operating in the
globally available licence-free 2.4GHz
Industrial, Scientific and Medical (ISM)
band, the nRF24AP1 has been intentionally
engineered for simplicity and efficiency.
A typical use case is a group of runners
each monitoring their heart rate and
speed with the data from the wireless
sensors being communicated to a sports
watch. The nRF24AP1 meets the tough
power constraints of this coin cell-powered
application while its Time Domain Multiple
Access (TDMA)-like adaptive isochronous
interference avoidance scheme ensures none
of the signals clash. The protocol is able to
Figure 1: A simple wireless
sensor network
4 NORDIC WIRELESS QUARTER Q4 2007
With the nRF24AP1, a cyclist
can monitor their heart rate and
speed using wireless sensors that
communicate data to a sportswatch
“The nRF24AP1 ably meets the battery life, size and system cost
requirements of wireless sensor networks”
support multiple data transfer modes up to
20kbps net data rate (transmitting at 1Mbps
raw data rate).
The nRF24AP1 is ideally suited to all
forms of WSNs used to monitor and control
systems in the sports, wellness, home and
industrial sectors. These types of networks
are forecasted to grow exponentially in the
next five years and are characterised by
low data rate transmission
of small amounts of sensor
information between
tens or even hundreds of
interconnected devices.
Typical applications
measure parameters that
don’t change rapidly (for
example, temperature or
humidity) so updates every
few seconds are satisfactory.
Technologies such as
Bluetooth wireless technology
and Wi-Fi® are designed to
transfer data much more
rapidly, so can’t meet the
special requirements of
battery life, size and system
cost of WSNs. In contrast,
the nRF24AP1 meets these
exacting requirements.
The ANT protocol
determines how one
wireless node communicates across a
wireless link with another by establishing
standard rules for co-existence, data
representation, signalling, authentication
and error detection. The protocol is critical
in ensuring reliable network transmission
over the specified range within demanding
power constraints. It includes features that
ensure ultra-low power consumption (down
to an average current draw of 10 microamps
in continuous operation) and constant
monitoring of the integrity of the link.
Networking with the nRF24AP1
Each wireless networking sensor, controller
or actuator combines with an RF transceiver
to form a network node. The abstract model
of the transceiver comprises a physical layer
(PHY), such as the nRF24AP1, protocol stack,
such as ANT, and an application layer that
forms the specific instruction set for the
application supported by the network.
The nRF24AP1 is a compact solution
requiring lower microcontroller resources
outside the radio than, for example, ZigBee,
considerably reducing system costs.
Each nRF24AP1 channel consists of one
or more transmitting nodes and one or
more receiving nodes depending on the
network topology. Any node can transmit
or receive so the channels are bi-directional.
In addition, every node is capable of
TECHNICAL BRIEFING
determining the best time to transmit
based on the activity of its neighbours, so no
coordinator or supervisory node is required.
(See figure 1.)
nRF24AP1 with ANT accommodates
three types of messaging: broadcast,
acknowledged and burst (see Figures
2(a), (b) and (c)). Broadcast is a one-way
communication from one node to
another. The receiving node transmits no
acknowledgement. This technique is suited
to sensor applications and is field proven as
the most economical method of operation.
Acknowledged messaging confirms
receipt of packets. The transmitter is
informed of success or failure, although
there are no retransmissions. This technique
is suited to control applications.
Finally, nRF24AP1 can use burst
messaging; this is a multi-message
transmission technique using the full data
bandwidth and running to completion.
The receiving node acknowledges receipt
and informs of corrupted packages that the
transmitter then resends. The packets are
sequence numbered for traceability. This
technique is suited to data block transfer
where data integrity is crucial.
The nRF24AP1’s ability to build a WSN on
an ad hoc basis simplifies interconnection.
Nodes can easily join and leave the network
and fewer system resources are required.
The nRF24AP1 is an ideal protocol for WSNs
because of its inherent ability to support
ad hoc interconnection of tens or indeed
hundreds of nodes.
Other technologies – such as ZigBee –
complicate network building by introducing
“reduced function” (i.e. devices that can
only operate as slaves), “full function” (i.e.
devices that can only operate as masters) and
coordinator nodes. These are distributed
throughout the network to supervise subsets
of nodes, adding complexity and increasing
system resources. The coordinator first
forms a subset cluster and then handles
requests from neighbouring coordinator
nodes wishing to attach their clusters to the
overall mesh (see figure 3). Such networks
can’t be constructed on an ad hoc basis,
which then makes it difficult for nodes to
join and leave.
The ANT protocol
The ANT protocol is characterised by its
low overhead that enables it to operate
efficiently with minimal system resources
and ultra-low power consumption at
low cost. It features low latency and the
ability to trade-off data rate against power
consumption. ANT is a production-proven
protocol designed for maximum flexibility,
scalability and ease-of-use, with integrated
Figures 2(a), (b) and (c): nRF24AP1 messaging
types; broadcast, acknowledged and burst
to send back an acknowledgement that the
message was either received OK, or should
be resent.
Data is sent across a wireless link in
packets of a predetermined size. Each
packet comprises an overhead (information
required to set-up the communication
with a specific node and to determine how
the information will be reliably sent) and
payload (the actual useful data). Information
too large to be sent using a single packet is
broken down into a number of standard
packets and re-assembled at the receiver.
In ANT’s case, the bits required to set-up
communications are minimised so that a
packet is shorter for a given payload. The
efficiency of a protocol is measured by the
ratio of overhead to payload. For example,
one generic protocol competing with ANT
features a packet of 160 bits comprising 128
bits of overhead and 32 bits of data yielding
an efficiency of 20 percent. In comparison,
ANT’s efficiency is 47 percent.
The efficiency of the protocol
– combined with the radio’s bandwidth
– largely determines the battery life of the
transceiver. The nRF24AP1 combines the
highly efficient ANT protocol with a raw
data bandwidth of 1Mbps (compared to
ZigBee’s less efficient protocol and 250kbps
raw data rate). Consequently, the nRF24AP1
can be engineered to spend long periods
in ultra-low power sleep mode (consuming
just microamps), wake up quickly, transmit
rapidly (because consumption rises to tens
of milliamps during transmission) and then
return to sleep mode.
network and channel management.
Standards-based protocols such as
Bluetooth wireless technology and ZigBee
(based on IEEE802.15.4) are loaded with
extra features that typically creep into
consortia specs in order to keep all
contributing parties happy. This increases
the protocol’s size, reducing efficiency and
increasing power consumption.
A protocol stack determines how
communication across a wireless link is
handled by establishing standard rules for
co-existence, data representation, signalling,
authentication and error detection.
Perhaps more importantly, a protocol
also has to be able to routinely handle
situations where several devices are trying
to communicate simultaneously.
A protocol determines how these
communications are handled
so that devices can co-exist and
broadcast routinely. In WSNs with
complex networks, ANT is able to
manage hundreds of nodes such
that transmissions do not clash or
interfere with each other.
A protocol is designed to
Figure 3:
suit specific communications
Some wireless
requirements depending on the
technologies,
constraints of a given application.
such as ZigBee,
For example, ANT is designed
employ nodes
with varying
primarily for sensor networks;
capabilities
data from the sensor is periodically
to construct
broadcast across the link to a
networks,
supervisory system. If data is sent
complicating
but occasionally not received this
the process
is not a problem because another,
updated transmission follows soon
after. However, if it’s essential that
every piece of data is received – for
instance when data is being backedup – the protocol would include
instructions for the receiving node
NORDIC WIRELESS QUARTER Q4 2007 5
www.nordicsemi.com
WIRELESS NET DESIGN LINE
Avoiding interference on the 2.4GHz
wireless desktop
The 2.4GHz band is home to so many competing RF sources that an effective
interference avoidance scheme is mandatory. But in battery-powered
applications, standards-based synchronised schemes aren’t a good choice.
Thomas Embla Bonnerud explains
C
ontemporary IEEE.802.xx standardsbased wireless technologies such as
Wi-Fi, Bluetooth wireless technology and
ZigBee crowd into the 2.4GHz band,
along with various forms of wireless Ethernet
and USB. In addition, many proprietary
manufacturers, including Nordic
Semiconductor, use 2.4GHz technology.
There are several established
techniques for ensuring
communications in the presence
of interference – including the
bullish approach of simply repeating
the transmission on high power until it
finally gets through to the elaborate direct
sequence and frequency hopping spread
spectrum schemes used by Wi-Fi, Bluetooth
wireless technology and ZigBee.
These latter schemes work well, but
when it comes to ultra-low power wireless
connectivity – where the unit’s current can’t
exceed the peak current of coin cells or other
small batteries, and the batteries need to last
for months or even years – these schemes
demand more power than is available.
Consider wireless peripherals for a PC.
End users expect to use several 2.4GHz
peripherals simultaneously (e.g. keyboard,
mouse, gamepad and for the latest media
centres, RF remotes) often in very close
proximity to Wi-Fi and Bluetooth-equipped
products. To meet consumers’ expectations
2.4GHz peripherals must communicate
with no loss of user data and remain highly
responsive even in the presence of other
active 2.4GHz RF sources.
Interference avoidance
The three popular IEEE-based wireless
technologies, Wi-Fi/ZigBee and Bluetooth
wireless technology employ Direct Sequence
Spread Spectrum (DSSS) and Frequency
Hopping Spread Spectrum (FHSS) schemes
respectively to maintain link integrity.
These work well, but they do add a
“Nordic Semiconductor’s recently
released nRF2601 Wireless Desktop
Protocol (WDP) is well suited to devices
with limited battery power”
The wireless desktop is
no place for peripherals without
good 2.4GHz interference immunity
significant communication overhead. For
low data throughput systems like mice and
keyboards, the overhead and hence power
consumption penalty means battery life falls
short of consumers’ demands.
In the case of FHSS (and other solutions
based on synchronous protocols), the
overhead is in the form of synchronisation
exchanges over the air that occur whether
the system is transferring useful data or not.
This synchronisation ensures that all the
participating devices hop between allocated
frequency channels simultaneously.
In DSSS, the overhead comes in the form
of the spreading codes sent instead of the
raw user data. This causes a DSSS system to
transfer a higher volume of data than would
be the case with just the raw data, increasing
power consumption. Both FHSS and DSSS add
complexity and represent a fixed overhead
because neither can be reduced or switched
off when little or no interference is present.
AA, AAA or coin cell powered-devices such
as mice and keyboards struggle to cope with
FHSS’s fixed overhead. ZigBee, championed
as a “low power” technology and using DSSS,
TO SEE THE ORIGINAL ARTICLE GO TO: http://www.wirelessnetdesignline.com/howto/202803164
6 NORDIC WIRELESS QUARTER Q4 2007
is undoubtedly easier on batteries than
Bluetooth wireless technology but targets
an entirely different market with low duty
cycle sensors and support for complex mesh
networking. ZigBee’s power consumption
(and complexity) make it unsuited to wireless
desktops that don’t need such features.
In comparison, Nordic Semiconductor’s
recently released nRF2601 Wireless Desktop
Protocol (WDP) is well suited to devices with
limited battery power. The WDP uses the
high speed features of the Nordic nRF24L01
transceiver. While running on the nRF24L01
chip (consuming around 12mA (peak) when
transmitting or receiving at 0dBm and
2Mbps) with typical usage patterns, the WDP
endows a wireless mouse with a battery life
of a year on two AAA batteries compared to a
month for an equivalent Bluetooth mouse.
An asynchronous protocol
The WDP only changes frequency channel
if transmission conditions deteriorate on
the channel in use. If the channel needs to
PRESS ARTICLES
Figure 1(a): WDP in low latency mode: The host constantly monitors predetermined channels waiting for a communication initiated by the device
Figure 2(a) above and (b) below: Latency and power consumption
increase with number of retransmits
Figure 1(b): WDP adapts to interference on channel 1 (“F1”) by shifting the
device’s transmitting frequency to channel 2 (“F2”)
be changed, the new one is selected from a
“channel table” subset of allowable 2.4GHz
channels known to both host and device.
The system is asynchronous – i.e. there
are no fixed timeslots – so there is less added
latency when retransmits are required, quick
transition from sleep mode to data transfer
and an inherent ability to scale to several
devices. (The WDP has native support for up
to five). Moreover, power consumption in the
peripheral devices is minimised, as there’s no
requirement for synchronisation beacons. It’s
important to note the star network formed
between the PC host and peripheral devices
is not a Personal Area Network (PAN) like that
formed by a Bluetooth master and its slaves.
With the WDP, each peripheral device has
no knowledge of its companions, and isn’t
synchronised to their communications.
The WDP host has two modes of operation,
low latency and low power. In the first mode,
because the PC powers the USB donglemounted transceiver, there is no current
rationing (nonetheless, RF front end current
is still only 12.3mA). However, if the PC goes
into sleep mode and suspends the USB bus,
the protocol can enter a low power mode and
reduce the drain to a minimum, enabling the
application to meet, for instance, the 500µA
average USB suspend mode requirement.
Remote wake up is maintained in this mode.
Moreover, this mode is very useful in meeting
other power rationing demands in the host
such as those needed to meet ‘green’ marking
of an end product.
In the low latency mode, the host (typically
a USB dongle on the host PC) monitors all
channels in the channel table for the same
duration in continuous rotation. In the
low power mode, channels are monitored
infrequently in a “burst-like” way; in between
bursts, the transceiver enters a sleep mode.
When initiating a transmission the device
(mouse, keyboard or remote control) wakes
up from sleep and transmits the data a userdefinable number of times on the previously
used good channel – so if no interference is
detected, communication is re-established
within a few milliseconds depending on the
number of RF channels the WDP utilises.
However, if after the defined number of times
the device is unable to communicate with
the host it will switch to another channel (in
130µs) as defined in the channel table.
The channel table is continually adapted
to take into consideration other WDP-based
desktop peripheral systems in the area
– so after a short period of operation, the
likelihood of multiple systems trying to
communicate on the same channel is low.
Figure 1(a) shows the scheme operating in
low latency mode. The host cycles through a
configurable number of RF channels (3 in this
case). The listen time on each channel must
accommodate two transmission (TX) attempts
from a device (in a typical PC peripheral
set up this will be typically 700 to 800µs).
Meanwhile, the device transmits on a single
channel (channel 1). (Note that by using the
Enhanced ShockBurst feature of nRF24L01 it
can do this in short bursts, minimising the
time on air and allowing the device radio to
return to the standby mode quickly where it
consumes just tens of microamps).
In this example, the first four bursts
coincide with the host’s time scanning
channels 2 and 3, so no acknowledgment is
received. When the host returns to channel
1 it coincides with the device channel;
the packet is received by the host and an
acknowledgment is sent back. The host and
device then exchange the data. For devices
with fixed report rates (like mice), the WDP in
the device keeps track of the host timing and
adjusts the first transmission attempt of the
next report to coincide with when the host is
back on channel 1. For non-fixed report rate
devices (keyboards and remotes), the device
simply goes to sleep and runs a similar linkup attempt the next time a button is pressed.
Even with a worst case link-up delay like that
shown in Figure 1(a) the link up time is still
less than 3 x 700 to 800µs (2.1 to 2.4ms).
Figure 1(b) shows what happens if
interference is encountered. If channel 1
becomes blocked by a competing RF source,
the device first tries communicating on the
last known good channel for a duration equal
to that of the host cycling through all used
channels, before switching to channel 2. Once
the host is on channel 2 it acknowledges the
transmission and communicates on the new,
clear channel (that is used from then on).
Latency and RF power consumption in the
device increase linearly with the number of
retries performed by the nRF24L01. Figure
2(a) illustrates the added latency against
number of retransmits, adding up to just over
3.5ms for eight retransmits. Figure 2(b) shows
the average nRF24L01 current consumption
against the number of retransmits.
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Battery life is critical in wireless desktop
applications and batteries don't last all that
long when standard-based interference
protocols are applied. Here's a
lower-power way to co-exist.
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Wireless Portal Technology — An Overview and
Perspective
MD8470A Speeds Development of Video Chips for Cell
Phones
The Building Blocks of a Wireless Communications
System
WiMAX: IEEE 802.16e-2005 — Introduction to OFDMA
Measurements
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Applications
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Phones
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Alliance Approach to Certification
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SDR folks (NXP calls its
embedded vector processor
an SDR solution) should sit up
and take notice. I was under
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component was the toughest
nut to crack. Maybe NXP had
done it.
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UWB on ice?
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How to mitigate 802.11n interference with PC peripherals
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IBM says the new capabilities
will expand the role of
self-managing, self-healing
computing systems.
CSR sees sales, margins
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increase in Q3
Big operators, vendors join
Femto Forum
Linux developers give
Google a belated welcome to
mobile party
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The full version
of this article was
originally published
in Wireless Net
Design Line. This
website is part of
CMP’s “TechOnline
community” and
has a subscriber
base of 8500
wireless specialists
Comments for: "GPS on
steep ramp in cellphones"
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MORE FORUMS
NORDIC WIRELESS QUARTER Q4 2007 7
www.nordicsemi.com
BLUETOOTH EVOLUTION CONFERENCE REPORT
Will ULP Bluetooth wireless
technology shape up for healthcare?
At the recent Bluetooth Evolution Conference* in London, the key
applications for ultra low power (ULP) Bluetooth wireless technology
were described. One of the most hotly debated applications was
healthcare, reports Thomas Embla Bonnerud
8 NORDIC WIRELESS QUARTER Q4 2007
ULP Bluetooth wireless technology
will enable unobtrusive monitoring
of health indicators – which can then
be relayed via a cellphone – while
patients go about their normal lives
PHOTO COURTESY OF BLUETOOTH SIG
H
ealthcare is crying out for a
standardised wireless solution
such as ultra low power (ULP)
Bluetooth wireless technology.
At present, hospitals and healthcare
institutions all over the world use a wide
range of fragmented systems for tracking,
monitoring and recording patients and
their medical data both within hospitals
and at home.
While out of necessity, management
methods and approaches have evolved to
work around the challenge, the disjointed
nature of patient monitoring and tracking
between various treatment inpatient and
outpatient stages (including the home) is
ripe for higher efficiency and, thus, lower
cost approaches. ULP Bluetooth wireless
technology could be the enabler for many
new approaches.
ULP Bluetooth wireless technology
could be used to allow automatic wireless
tracking and monitoring of patients
via dedicated, ULP Bluetooth wireless
technology-enabled instruments and
wearable sensors from the moment they
come into contact with the healthcare
provider, until the moment they leave the
system. These systems could be engineered
to seamlessly handover from one treatment
phase to the next, while at the same time
giving healthcare staff rapid access to
information telling them everything that
has gone before.
Tracking and monitoring technology
needn’t be restricted to inpatient and
outpatient facilities at the hospital. It
is perfectly suited to extend to patients’
homes. Indeed, as it was explained at
the conference, the unobtrusive nature
of wireless technology ideally matches
the trend in healthcare towards making
sure people are treated in hospitals and
healthcare institutions when it is the only
“The unobtrusive nature of wireless technology ideally
matches the trend in healthcare towards making sure people
are treated in hospitals when it is the only alternative”
alternative. This trend is only likely to
accelerate as healthcare costs escalate.
ULP Bluetooth wireless
technology in health
ULP Bluetooth wireless technology would
enable wireless monitoring and hence
remote management of what are fast
becoming today’s big killers: the chronic
diseases such as hypertension (blood
pressure), heart disease and diabetes.
Another market with huge potential
for ULP Bluetooth wireless technology
in healthcare is enabling elderly
independence – i.e. giving the elderly
the ability to age with dignity, for as long
as possible, in their own homes. With
greying populations in the developed and
developing world growing, managing the
cost of treating and caring for the elderly is
BRIEFING
fast becoming one of the key contemporary
political issues.
Potentially, ULP Bluetooth wireless
technology could be part of the solution
– one that not only meets the financial
restraints of healthcare providers and
governments, but that also gives elderly
people what they want: a chance to live
independently for as long as possible.
In reality, this means automating the
monitoring and care of large numbers of
people at home, and minimising costly
home visits.
With the appropriate infrastructure
(see sidebar below “A friend of the sick”)
ULP Bluetooth wireless technology could
be used to remotely monitor correct
intake of medication, whether the user
had successfully got out of bed and eaten
on time, and, in a less palatable but
nonetheless equally important role, for
personal cleanliness monitoring after
bouts of incontinence.
Too early to predict
Although the case and potential for ULP
Bluetooth wireless technology in healthcare
was made quite strongly during the
conference, it has to be stressed that its
adoption – or more particularly speed of
adoption – was heavily debated.
A number of attendees felt that the
universal use of ULP Bluetooth wireless
technology in healthcare – although
technically feasible and eminently desirable
– was years from adoption and that any
discussion of likely product applications
and volumes was woefully premature.
Although certain senior speakers from
the healthcare sector said ULP Bluetooth
wireless technology was what the sector
had been demanding, the doubters
cautioned that healthcare was a naturally
conservative market and that the decision
makers of that industry would need a lot
of convincing about the performance and
reliability of the technology.
Moreover, it was noted that attempts
to introduce wireless into the healthcare
sector in the past had resulted in a loss
of credibility due to technical problems
relating to poor interference immunity.
In a healthcare environment, there
are likely to be many wireless sensors
and devices transmitting in close vicinity
to each other. While ULP Bluetooth
wireless technology’s frequency hopping
schemes will almost certainly be more
than capable of handling such hostile
radio environments, a cynical medical
community will need some convincing.
That said, ULP Bluetooth wireless
technology is unlikely to ever be used
in safety-critical areas (i.e. in intensive
care or emergency room systems that
keep patients alive) because of the use
of the unlicensed ISM band. This would
be because performance could not be
guaranteed (and litigation issues are the
core worry here) to meet the required
medical-grade availability and reliability
standards, potentially leaving makers
exposed to crippling legal suits.
A long haul to adoption
The overriding message from the
conference was that while ULP Bluetooth
wireless technology has enormous
potential in healthcare – for in-house and
home-based patient tracking, monitoring
and medical data recording – many
observers still predict a long haul, rather
than immediate wave of adoption.
This conclusion is despite the fact that
ULP Bluetooth wireless technology addresses
one of the healthcare industry’s biggest
challenges – cost effectively keeping
greying populations out of hospital and in
their homes for as long as possible.
All this, however, is unlikely to afflict
another of ULP Bluetooth wireless technology’s
prime target sectors: sports equipment. Here,
ULP Bluetooth wireless technology-enabled
applications could well appear even before
the end of 2009. For more on this, look out for
the first issue of The Wireless Quarter in 2008.
* Organised by IMS Conferences – see www.
imsconferences.com/bluetooth
Thomas Embla Bonnerud is Product
Manager Standard Components with Nordic
Semiconductor. Bonnerud presented at the
Bluetooth Evolution Conference and sat on several
Q&A panels at the event.
A friend of the sick
ULP Bluetooth wireless technology’s
interoperability and ability to run from 3V coin
cell batteries for up to a year make it an ideal
technology for unobtrusive monitoring.
In one suggested application scenario,
patients carry on their daily lives at home
while ULP Bluetooth wireless technologyequipped sensors monitor vital signs such as
blood pressure, temperature, blood glucose
or heart rate.
In addition, motion sensors could be used
to indicate whether medicine containers had
been accessed at prescribed times, or whether
patients were moving around the house
in a normal routine (rather than remaining
stationary which could indicate lack of self care).
Standalone ULP Bluetooth chips fitted to
these wireless sensors are able to run off coin
cells for long periods due to very low duty cycle
operation and ultra-low power consumption.
These chips enter ultra-low power sleep modes,
ULP Bluetooth is an ideal technology for unobtrusive monitoring
waking periodically to send data in short bursts,
utilising the 1 to 2 Mbps bandwidth of ULP
Bluetooth wireless technology, before returning
to sleep mode.
Data is transmitted to a cellphone or PC
equipped with a dual mode ULP Bluetooth
chip. The cellphone or PC saves the data before
periodically transmitting it via the local GSM
system or over the Internet for interpretation by
healthcare professionals.
NORDIC WIRELESS QUARTER Q4 2007 9
www.nordicsemi.com
ESM CHINA
ULP Bluetooth wireless technology and
ZigBee compared
ESM China recently interviewed Chim Chan, Nordic’s Greater China
sales manager about ultra low power (ULP) Bluetooth. This is an
excerpt from the interview published in ESM China’s September 2007
print issue and online
ESM China (ESMC): What are the
differences between ULP Bluetooth
wireless technology and ZigBee?
Chim Chan (CC): Nordic Semiconductor is
not a supplier of ZigBee, so I can only make
general statements about that technology.
My understanding is that ZigBee is
targeted at mesh networking where power
consumption and cost are constraints.
Typical applications are home automation,
industrial networking and other wireless
sensor networks where many sensors need
to transmit relatively small amounts of data
relatively infrequently. Consequently, the
radio can spend much of its time in a lowpower “sleep” mode, saving battery capacity.
Backed by an alliance of powerful silicon
vendors, ZigBee is based on the IEEE 802.15.4
standard PHY (the actual radio) and Media
Access Control (MAC) layers, supporting
the alliance’s own Network (NWK) and
Application (APL) layers. It can transmit
on either 868 or 915MHz, or 2.4GHz. Most
development efforts are focused on the
2.4GHz band as this is generally accepted as
the ‘global’ licence-free band and allows the
highest transmission rates (up to a claimed
250kbps “raw” data rate).
Compared to Bluetooth wireless technology
– which is designed for larger bandwidth,
higher duty cycle file transfers, for instance
cellphone to PC – ZigBee is undoubtedly
cheaper, simpler and more power efficient.
But it is not the optimum engineering
solution for mesh networking applications.
Proprietary alternatives – such as our
nRF24AP1 running the ANTTM protocol – use
far less power, are comparable in price,
simple to implement, scalable and proven.
Perhaps that’s why ZigBee has so far failed
to catch the engineering community’s
attention – but this is a conversation for
another time.
Furthermore, because it is designed for
large static networks, ZigBee is ill-suited to
10 NORDIC WIRELESS QUARTER Q4 2007
the ad hoc star networks typical of consumer
electronics applications.
Nordic Semiconductor has been very
successful in leading the ultra-low power
short-range wireless connectivity niche for
consumer applications with its proprietary
technologies. For example, Nordic’s
nRF24xxx family of 2.4GHz transceivers are
used in millions of wireless mice, keyboards,
health sensors and sports watches across the
globe. The company’s success is founded on
products that are simple to build-in, use little
power, are immune from interference from
other 2.4GHz radios, and are cost-effective,
compact and robust.
But, as with all proprietary technologies,
Nordic’s transceivers lack the ability to
interoperate with 2.4GHz devices from
other manufacturers. That’s why Nordic
Semiconductor decided to become a
founder member of the Wibree Alliance, an
open industry initiative driven by handset
manufacturer Nokia and set up to promote
interoperable ultra-low power wireless
transceivers. In June, Wibree was adopted by
the Bluetooth SIG and renamed ULP Bluetooth
wireless technology.
The Bluetooth SIG appreciates that its
current technology is limited to applications
with relatively large (often rechargeable)
batteries. The SIG knows that its members
want to embed wireless connectivity into
“The Bluetooth SIG knows
that its members want to
embed wireless connectivity
into everything from
biomedical monitors, to
watches, toys, and sports
goods. ULP Bluetooth wireless
technology fills this gap”
everything from biomedical monitors, to
watches, toys, and sports goods (such as
linking a sensor in a running shoe to an MP3
player). ULP Bluetooth wireless technology
fills this gap. Note that what I say here about
ULP Bluetooth wireless technology is based on
provisional information and could change
when the final specification is published.
ESMC: How is progress towards ZigBee
single-chip integration and the ULP
Bluetooth interoperability specification?
CC: Again, it’s difficult for me to
comment specifically on ZigBee as Nordic
Semiconductor is not part of that initiative.
But as an outsider, I’m not aware of many
efforts to integrate ZigBee onto a single
chip. It’s a tough challenge because
PRESS ARTICLES
PHOTO COURTESY OF FRWD TECHNOLOGIES
ZigBee does have quite a large protocol
demanding the resources of relatively
powerful microcontrollers. Integrating a
microcontroller and ZigBee radio onto a
single chip is possible, but it’s going to be
difficult to keep the price down.
Regarding ULP Bluetooth wireless
connectivity: Nokia, Nordic Semiconductor
and other members of the Wibree Alliance
were aiming to release the Wibree spec
during the first half of 2008. As far as I know,
this date has not significantly changed
now that the Bluetooth SIG is in charge of
producing the ULP Bluetooth specification.
I read somewhere that the Bluetooth SIG
Above, the sports sector is a prime target for
ULP Bluetooth
PHOTO COURTESY OF BLUETOOTH SIG
Left, initial applications for ULP Bluetooth
technology will include PC peripherals
expects members to be producing sample
dual mode parts before the end of 2008.
Nordic Semiconductor plans to introduce
samples of its standalone devices before the
end of this year.
There is currently no information
regarding whether the Bluetooth SIG plans
to significantly change the draft Wibree
specification, but I think that the SIG would
prefer to keep the changes to a minimum.
ESMC: What are the target markets for
each technology? How do you think the
two technologies will co-exist?
CC: The envisaged market for ULP Bluetooth
wireless technology is clear. It is targeted
at those manufacturers who want to add
a low cost, ultra-low power, robust 2.4GHz
wireless link to their product in order to
transmit small volumes of data to a central
resource such as a cellphone or PC. Because
ULP Bluetooth wireless technology can run
from coin cell batteries, it can be integrated
into thousands of low-power items which will
form PANs with dual mode Bluetooth chipequipped devices.
Initial applications for ULP Bluetooth
wireless technology include leisure,
healthcare, entertainment and office. So, for
example, a person taking a workout could use
their smartphone equipped with a Bluetooth
dual mode chip as the centre of a PAN
comprising ULP Bluetooth wireless technology
equipped running shoes, ULP Bluetooth
wireless technology-equipped heart rate
belt and ULP Bluetooth wireless technologyequipped sportswatch. It’s also possible
that this data could be sent to a suitably
equipped GPS unit that could be used to
make predictions about where the user will
be physically located in the future based on
their current rate of progress.
Again, commenting as an outsider, ZigBee
is targeted at mesh networking applications,
sometimes called wireless sensor networks.
These applications require large numbers
of inexpensive nodes running for years
on batteries. I can see the need for such
applications – after all, we already deal with
such customers because they often select our
nRF24AP1 because it’s perfect for the job.
Despite the hype, practical implementations
of ZigBee are rare, because it’s still relatively
expensive, hard to set up, and battery life is
proving disappointing. Because of this, I see
proprietary technologies dominating this
sector for some time yet.
Because ULP Bluetooth wireless technology
and ZigBee are different technologies,
targeted at consumer oriented PANs and
wireless sensor networks respectively, there
is little or no chance of co-operation and
integration. The Bluetooth SIG and ZigBee
Alliance have never worked together, and ULP
Bluetooth wireless technology – as an extension
of the existing Bluetooth specification – isn’t
going to change that.
I think the technologies will co-exist,
providing ZigBee can resolve the problems it
has with practical implementations, because
the market for wireless technologies will be
so big. ULP Bluetooth wireless technology has a
bright future because it is a logical extension
of a mature and proven technology.
ESMC: What do you think are the main
challenges in the market promotion of
Zigbee/ULP Bluetooth technology?
CC: ZigBee is struggling to find a niche
because cost, battery power and ease-ofimplementation aren’t living up to the hype.
ZigBee really isn’t “Wireless control that
Simply Works”, despite the slogan.
ULP Bluetooth wireless technology is still
at the draft stage and engineers are waiting
to see how long the standard takes to be
ratified. But ULP Bluetooth should reach the
market much quicker than Bluetooth wireless
technology did because it is already at such an
advanced stage – Nokia has been working on
this technology since 2001, and the Wibree
forum have been drafting the specification
since October 2006. In addition, Nordic is
developing the hardware and software right
now, and Bluetooth chip suppliers are busy
working on the dual mode chips.
Probably the only major issue to rapid
uptake of ULP Bluetooth is fear among non-RF
designers about designing-in the technology.
Nordic Semiconductor works with these type
of customers all the time and we overcome
these fears by offering comprehensive “RF
Silicon Solutions” in the form of chips,
software, development kits and reference
designs to lower the learning curve and
accelerate time-to-market.
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An edited version of this
article was originally
published in ESM China.
ESM China is published
in Simplified Chinese
and distributed to a
BPA audited circulation
of over 36,000
Chinese engineering
professionals
NORDIC WIRELESS QUARTER Q4 2007 11
www.nordicsemi.com
THE PEOPLE & FACES
Behind Nordic Semiconductor
Bertel-Eivind Flaten
R&D Director
The nRF24LU1
(see front cover) is
the latest Nordic
transceiver to redefine
what’s possible at
2.4GHz
“Nordic
Semiconductor
is now widely
regarded as
the leading
expert in ultralow power
2.4GHz wireless
technology”
Hi. My name is Bertel-Eivind Flaten and I’m Director of
Research & Development (R&D) at Nordic Semiconductor.
I’m responsible for the development of all new Nordic 2.4GHz
components at our R&D headquarters in Trondheim, Norway.
I’ve been with Nordic since June 1996, when my first
task was to map out the company’s strategy for making the
wholesale shift to becoming a supplier of standard wireless
components and all the technical R&D challenges and
implications this would entail.
A year later, the strategy was formalised and I was
privileged to become the R&D Director within the newly
formed wireless components division. I passionately
wanted the initiative to succeed given that in large parts
it included my original proposal.
Thankfully, moving to standard wireless components has
proved to be a very successful strategy for the company both
technically and commercially. As a result I was promoted to
R&D Director for the entire company two years ago. This work
includes the development and rollout of our first ultra low
power (ULP) Bluetooth transceiver.
Nordic Semiconductor is now widely regarded as the
leading expert in ultra-low power wireless (basically 3V
coin-cell powered and/or one-year plus battery lifetimes)
technology – whether it’s Nordic’s proprietary 2.4GHz
technology today or standards-based ULP Bluetooth
tomorrow. Ultra-low power wireless is all we focus on.
While it is an honour to be perceived as the leading expert,
it also makes Nordic a prime target for competitors, and
responsible for establishing cost, power and performance
benchmarks for ultra-low power wireless. That’s a huge
responsibility on my department’s shoulders: It means we
have to continue to develop 2.4GHz transceivers – currently
in and around the 1-2Mbps data rate performance envelope
– that meet the core wish list of customers and that no other
semiconductor rival can match, no matter how hard they try.
As director of R&D it’s my job to lead and motivate our
technical development teams to meet this objective – not
only during the good times – but also during the darkest and
most punishing moments. These are the moments when the
temptation is to accept “good enough” but when the right
decision is to work harder to attain genuine excellence.
This means at times having to solve problems that initially
seemed impossible; backing maverick engineering ideas
because “they might just work”; but knowing when to steer
well clear of other ideas we instinctively sense will never
work (wisdom, as they say, is knowing the difference).
While this does occasionally mean working through
the night and consuming pots of strong coffee in order to
hit deadlines, when we hear of yet another global brand
designing-in Nordic technology to their latest product it
makes it all worth it – in an instant.
I don’t for one moment accept any more than a tiny part
of the credit for the results – such as Nordic’s newly launched
nRF24LU1 2.4GHz transceiver – because our success is due to
the collective brilliance and ambition of our technical teams,
and that’s far greater than the impact of any one person.
The other side of R&D is technical support: giving
customers the critical advice that enables them to designin our products quickly without getting hung up on the
inevitable technical queries and issues that may occur.
One of the things I really like about my job is that every
single day there is a new challenge that can’t necessarily
be solved with a standard approach. You have be prepared
to think laterally and draw upon the collective experience
and expertise of the teams. I love that, because you come
away feeling that you have created something that was truly
better than the sum of its parts.
Outside of work, I enjoy Norway’s summer months where
it’s daylight most of the time. This is in complete contrast
to the winter months where in northerly Trondheim it’s
dark most of the time. Although the glorious Northern
Lights - once believed in ancient times to be the sprits of
dead Norwegian warriors but now known to be the Earth’s
magnetic field deflecting fast moving charged particles from
the Sun - go a long way to make up for it.
I also love hiking and skiing in the beautiful, serene and
somewhat deserted Norwegian mountains we are so lucky
to have here. The nearest most people are likely to get to this
experience is the cross trainer in their local gym (although a
lot of these will one day almost certainly carry Nordic ultralow power wireless technology so they’ll at least spiritually
be closer to the real Scandinavian thing).
Bertel-Eivind Flaten
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