Transcript Equinox: Subverting the Dominant Paradigm in Consumer

Equinox: Subverting the
Dominant Paradigm in Consumer
Electronic Design
John Miles
Introduction
- Who am I?
- “Beware of programmers with
screwdrivers.”
- I have a history of solving hardware
problems with brute force…
… and a
pronounced
tool fetish
Evolution of Equinox
Meet the ICF-CD873 …
Meet the ICF-CD873 …
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20 buttons on top surface
– Only “Snooze” is easily
recognizable by touch
– Impossible to set clock or
alarm by feel
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Blinding LCD backlight
Annoying “Voice Plus”
feature
– Never miss a 3:00 AM power
glitch again!
So, how do we fix it?
The ICF-CD873 is a good target for
mockery, because it’s a perfect example of
the “one size fits all” fallacy
 Your desired features != mine

– Maybe you want a radio with 20 buttons you
can’t see
– OK, enough about the buttons already, we get
the idea

Let’s define my feature list…
Wish List: Radio Performance
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True “DC to daylight” radio coverage
– Nowadays, this means at least DC-1 GHz
» Imagine a 25-foot long radio dial…
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All common modulation types
» AM for standard AM broadcast, aircraft
» WBFM for standard FM broadcast, TV audio
» NBFM for weather, Amateur Radio repeaters, public-service
bands
» SSB/CW for HF Amateur reception
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Oh, yeah… trunk-tracking scanners are hella cool.
I want one of those, too.
Don’t care about CDs…
Wish List: Clock Display
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Large clock display with automatic
dimmer
– I couldn’t read the Sony’s display from 3’
away without glasses
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Original plan was to use 1” LEDs
These gave way to Burroughs B7971
Nixies
Eventual solution: 7” LCD touchscreen
with rendered B7971s
– Even better solution: LASIK surgery :-P
Wish List: Features/Ergonomics

It wouldn’t have taken much for me to be OK
with the Sony’s feature set
– Front-mounted controls (or at least hapticallycorrect ones)
– Automatic time setting
– Battery backup
– No howlingly-stupid features (“Voice Plus”)
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Ability to access receiver from anywhere
The All-Important GAF
(Girlfriend Approval Factor)
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Receiver outgrew two smaller enclosures
4U rack-mount server chassis = bad news in the
bedroom, in more ways than one
Antenna connections, cabling also awkward
Ended up with dedicated client PC (Mini-ITX) in
receiver’s first enclosure choice
GAF/WAF isn’t just snarky sexism in action, but a
valid expression of a legitimate design goal.
A design that considers the needs and tastes of
“normal people” will LAST.
Technical Highlights
• Main Receiver
• Quad-conversion superheterodyne
• DC-1 GHz, all-mode coverage
• Auxiliary Data Receiver (ADR)
• Single-conversion, single-frequency superheterodyne
• Continuously monitors King County trunked-radio system
control channel at 868.175 MHz
Technical Highlights
• Each receiver has its own Atmel
ATMega128 microcontroller
• 8-bit 16 MHz CPU with 128K program
memory, 4K RAM
• Lots of parallel and serial I/O ports,
timers, ADCs…
• Supported by free AVR-GCC C++
compiler
• Atmel C++ code cross-compiles under
MSVC for module-level testing on bench
via parallel ports
• Board in photo is AVR-H128 from
www.sparkfun.com; many other
vendors offer similar development
boards
Technical Highlights
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Main and auxiliary receiver controllers interfaced to Via
EPIA Mini-ITX motherboard in server chassis via RS-232
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Trunking data (talkgroup updates, etc.)
Commands from server to receiver hardware on behalf of clients
Status/signal reports from receiver to server for distribution to clients
This is all low-bandwidth traffic (38.4 kbps, plain ASCII text for easy
diagnostics)
Audio output from main receiver demodulator assembly
sent to onboard audio line-in jack for digitization and
streaming
• Audio transmitted as 11 kHz mono
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Local clients get 16-bit PCM
Remote clients get ADPCM
Construction Example:
Main Antenna Input Assembly
•
Receiver is built as array of
interconnected modules
• Better for RF signal integrity
• Easy to change your mind!
• Modules can be reused as-is
in future revisions of the
project, or in different
projects altogether
•
Expensive parts like filters
and coax relays scavenged
from (formerly) high-end
telecom / test equipment…
Construction Example:
PLL Synthesized Local Oscillator
- Offers tuning resolution
and coverage normally
found in military /
government receivers
- This is the only
professional-quality
PC board in the receiver
- More R&D time
(months) than any other
assembly
Construction Example:
Second Converter Assembly
• Good example of “dead bug” home construction technique
• Even hardcore RF tinkerers don’t realize this technique is usable
beyond 1 GHz!
• Among the best ways to work with RF at the prototype level,
but…
• Testing is important, since you can’t always model or predict exact
circuit behavior
• This is where your equipment fetish can really save the day!
More Dead-Bug Action…
• Short leads on components,
direct connections to ground
plane make your circuit ugly
• That means ugly = good!
• Electrons have surprisingly-little
regard for aesthetics…
Design Resources
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Equinox receiver project page
www.ke5fx.com/equinox/equinox.html
» Download the client app and give it a spin!

John Miles, KE5FX, and Richard Hosking, VK6BRO,
“A Versatile Hybrid Synthesizer,” QEX, Mar-Apr 2004
» Also available online at www.ke5fx.com/synth.html
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Analog Devices ADIsimPLL design tool (www.analog.com)
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AVR-GCC multiplatform C++ compiler
(www.avrfreaks.net/AVRGCC/)
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QEX/Communications Quarterly
(www.arrl.org/qex)
Component Sources
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www.ebay.com
• Business & Industrial
• Industrial Electrical & Test
• Electronic Components
• Test Equipment
Alphatronics
• In Tukwila, not far from Fry’s and other attractions
http://shop.vetcosurplus.com/catalog/
• In Bellevue, great selection of RF coax/connector hardware, much more
www.digikey.com
• Largest selection / best service / moderate prices
www.minicircuits.com
• Personal financial Armageddon for the RF hacker
www.jameco.com
• Similar to Digi-Key
www.futurlec.com
www.sparkfun.com
• Good sources for microcontroller prototyping aids, other parts