Equinox Subverting the Dominant Paradigm in Consumer Electronic
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-CD 873 …
Meet the ICF-CD 873 … n 20 buttons on top surface – Only “Snooze” is easily recognizable by touch – Impossible to set clock or alarm by feel n n Blinding LCD backlight Annoying “Voice Plus” feature – Never miss a 3: 00 AM power glitch again!
So, how do we fix it? The ICF-CD 873 is a good target for mockery, because it’s a perfect example of the “one size fits all” fallacy n Your desired features != mine n – Maybe you want a radio with 20 buttons you can’t see – OK, enough about the buttons already, we get the idea n Let’s define my feature list…
Wish List: Radio Performance n True “DC to daylight” radio coverage – Nowadays, this means at least DC-1 GHz » Imagine a 25 -foot long radio dial… n 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 n n Oh, yeah… trunk-tracking scanners are hella cool. I want one of those, too. Don’t care about CDs…
Wish List: Clock Display n Large clock display with automatic dimmer – I couldn’t read the Sony’s display from 3’ away without glasses n n n Original plan was to use 1” LEDs These gave way to Burroughs B 7971 Nixies Eventual solution: 7” LCD touchscreen with rendered B 7971 s – Even better solution: LASIK surgery : -P
Wish List: Features/Ergonomics n 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”) n Ability to access receiver from anywhere
The All-Important GAF (Girlfriend Approval Factor) n n n Receiver outgrew two smaller enclosures 4 U 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 ATMega 128 microcontroller • 8 -bit 16 MHz CPU with 128 K program memory, 4 K 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-H 128 from www. sparkfun. com; many other vendors offer similar development boards
Technical Highlights • Main and auxiliary receiver controllers interfaced to Via EPIA Mini-ITX motherboard in server chassis via RS-232 • • • 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 k. Hz mono • • 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 n Equinox receiver project page www. ke 5 fx. com/equinox. html » Download the client app and give it a spin! n John Miles, KE 5 FX, and Richard Hosking, VK 6 BRO, “A Versatile Hybrid Synthesizer, ” QEX, Mar-Apr 2004 » Also available online at www. ke 5 fx. com/synth. html n Analog Devices ADIsim. PLL design tool (www. analog. com) n AVR-GCC multiplatform C++ compiler (www. avrfreaks. net/AVRGCC/) n QEX/Communications Quarterly (www. arrl. org/qex)
Component Sources • • 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
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