Yak-2 Hardware Design

$Id: design.html,v 1.10 2000/11/29 08:48:41 jani Exp $
$Revision: 1.10 $


As far as wearables go, the Yak-2 is pretty beefy in its capabilities. While still about 5 years behind the state of the art in desktop computing with a 233 MHz Pentium, 640x480 display, etc, it is still rather bulky for a wearable and an order of magnitude more expensive than an equivalent non-wearable. If you can make do with less (586/486, flash memory only, etc) you can also reduce the size, weight, power consumption and expense considerably.


Original aims

See Wearable Translator Specifications for details.

Learned the hard way from Yak-1

See Yak-1 Hardware Usability Assessment for details.

General wearable requirements derived from the above

Basic design

Yak-2 Wearable Translator block diagram

Hardware platform (CPU, interfaces)

Prepackaged commercial wearable solutions

Overpriced, underpowered, built for specific tasks and software, poor Linux support and very little room for hacking.

Name Pros Cons Assessment
Xybernaut MA IV Prepackaged but expandable
Commercial and available now
Standard x86 technology
Includes PCMCIA, USB, audio in/out, port replicator
Designed for Windows
Usability on Linux unknown but probably poor
Relatively overpriced and underpowered (Pentium 200, 64 MB, 4.2 GB = $4000!)
VIA II PC Prepackaged
Commercial and available now
Standard x86 technology
Designed for Windows
No VGA output without port replicator
Bulkier than Xybernaut MA IV
Less powerful/expandable than MA IV
Price unknown, no distributor in Japan
Xybernaut MA IV is considerably better in this category

Prepackaged non-commercial wearable designs

Don't reinvent the wheel, copy someone else... but how many of yesterday's designs are still valid today, and how many are suitable for your task?

Name Pros Cons Assessment
Charmed CharmIT Available pre-assembled...maybe?
Based on JUMPtec's PC-104 boards, Pentium 166/266
Built for Linux
2xPCMCIA, ethernet, USB, keyboard, display
Fits just one PC/104 expansion card: sound or PCMCIA, not both
No CompactFlash
Clunky aluminum case
Somewhat outdated and not suitably packaged for this project

Obsolete: MIT Lizzy, Steve Mann's WearComp6 (extensive documentation though, and lots of good tips!)

PC/104 SBC boards

Highly integrated SBC (Single Board Computer) motherboards standardized for the embedded market, vertically stackable with expansion cards, standard size around 100x140 mm. PC/104 is ISA only, PC/104+ uses PCI instead. See the PC/104 FAQ for details...

Advantech PCM-5822 102x145x20 mm, 220g, <10W/5V
Standard x86 (Cyrix Geode GX1 200,233,300)
2xUSB, IrDA, 100Base-T, CompactFlash (Type I only!), audio in/out...
Almost all connectors on board, no baseboard needed
TV out built-in (for retrofitting Glasstron!)
Predesigned casing available
PC/104 (ISA) expandable
Popular in the wearable community
Less than $1000 with the works
Available now
Distributor in Japan
Y4-5 man, delivery in 3 days to 1 month
IBM MicroDrive requires CF Type II
PCMCIA requires PC/104 expansion board
Audio recording does not work under Linux...yet?
Would be perfect without recording and MicroDrive problems
Remains the best option even without them
Ampro EnCore 500 100x145mm, ? g, ?W/5V
Standard x86 (Pentium 266)
4xUSB (!), 100Base-T(!), sound in/out
CompactFlash expansion (MicroDrive etc) available
PC/104+ expandable
Less than $1000 with the works
No packaging
PCMCIA requires PC/104 expansion
No connectors, but has grouped pins for cables
Available Dec 2000
Most interesting...
Cell Computing Plug-N-Run 233
w/ Net/SlotCARD backplane
PNR: 76x127x13mm, 100g, 2-10W/5-16V
w/ NetCard: 102x137x28mm, 226g, 10W(max)/6-16V
Standard x86 (Pentium 233)
(higher clock speeds also available, but power consumption is prohibitive)
2xUSB, 100Base-T, CompactFlash and 2xPCMCIA through NetCARD
PC/104+ expandable
No packaging
Sound requires PC/104 expansion card
PNR/NetCARD/soundcard stack is too thick and heavy

See also: JUMPtec MOPS

Other SBCs

Many truly tiny systems are not PC/104, but most are also underpowered, difficult/impossible to expand and/or require too much porting work for many applications...

JUMPtec ETX-P1 100x114x10(!) mm, ? g, 5-8W/5V
Standard x86 (Pentium 266)
3xUSB (!), 100Base-T(!), sound in/out
8 MB flash built in!
Custom-tweaked "EMF White Dwarf Linux" available
Basic board (no memory) $500
No packaging
No PCMCIA or CompactFlash expandability
No direct support for PC/104+ expansion
Bizarre custom connectors (optional baseboard is way too big, alternative is lots of custom cable soldering)
Poor expandability and custom connectors make this a risky choice
LART Fully open technology
Very low power consumption
Expansion boards available
Built for Linux
Not available commercially
Packaging not included
200 MHz StrongARM, not x86
No Java support (yet)
No speech recognition support (yet)
Would be #1 if not for extra effort required
Building a LART wearable would be an interesting project in itself!
TIQIT Matchbox PC Truly tiny (70x50x24 mm)
Standard x86 technology
Commercial and available now
Only 66 MHz
No facility for audio input/output
Not suitable for translation

See also: ZF Linux Devices MachZ, JUMPtec DIMM-PC, Cell Computing CardPC, Advantech Biscuit PC


Name Type Resolution Price Availability
(delivery time)
MicroOptical EG-7 Integrated eyeglass 640x400 color $6000? 2001?
Definitely the best of the bunch, but not yet available
MicroOptical CO-3 Clips onto glasses 640x400 color $3000 Jan 2001
Choice #1: resolution is more important than a bit of extra visibility
MicroOptical EG-? Integrated eyeglass 320x200 color $5000 Now
(6 weeks)
The most unobtrusive, but too low-res: no point in buying now with the 640x480 just around the corner
MicroOptical CO-1 Clips onto glasses 320x200 color $2500 Now
(1-2 weeks)
Obsoleted by CO-3
Shimadzu Data Glass 2 Monocular headband 800x600 color $500(?) Dec 2000?
Choice #2: All the functionality of the MicroOptical CO-3 in a slightly bulkier case at 1/6th the price
Liquid Eye M2 Monocular glass mount 800x600 color $5000 Now
(6 weeks)
Much too bulky
Liquid Eye M1 Monocular eye-patch 320x200 monochrome $500 Now
(next day)
A popular cheap solution, but unacceptably low-res

Non-monocular solutions: Sony Glasstron, Olympus Eye-Trek, Canon GlassType...

Research prototypes: IBM VisionPad, Minolta's new gadget...


Name Pros Cons Assessment
CompactFlash flash cards
No moving parts, thus effectively indestructible
Available at sizes up to 512 MB (see SimpleTech)
512 MB is still pretty small
Way more expensive than other solutions (512 MB costs $1,599!)
Not a replacement for a "real" hard drive, but needed to get system to boot
IBM MicroDrive Smallest drive on the market
43x37x5 mm, weight 16g
Up to 1 GB available
Uses CompactFlash for power & data
Requires large CompactFlash slot (not usable with Advantech PCM-5822)
1 GB is a bit on the small side
Very, very attractive, but requires PCMCIA adapter for PCM-5822 -- so we go for a "real" PCMCIA HD with more capacity instead
IOdata PCHDT-2Gt PCMCIA Type II card
86x54x5 mm, weight 55g
Capacity 2 GB
Data & power through PCMCIA
Available now (MSRP Y59,800)
Requires PCMCIA support
Most systems can't boot from PCMCIA
Still bigger than 2 MicroDrives
Excellent solution if system has a spare PCMCIA slot -- and with the PC/104 2-slot PCMCIA board Yak-2 does!
IBM TravelStar 100x70x9.5mm, weight 100g
4.7W peak, 2.3W use, 5V
Capacity up to 20 GB
Designed to take abuse
Standard IDE interface
Heavier and bulkier than CF solutions Provides major capacity, but it's either this or the 2-slot PCMCIA, not both


The only easy choice: almost all embedded systems use SO-DIMM "laptop memory", available in sizes up to 256 MB. 64 or 128 MB should be plenty. (We don't want too much, memory also sucks up juice...)


Choices, choices...

Input/output devices

Needed for translation system itself


Not needed for Yak-2 core functionality, but still a very good idea to have around... See also: Dauphin mini keyboard

Recycled from Yak-1

Power supply

Mounting and support

Name Pros Cons Assessment
L3 WristPC (aka Xybernaut XyberKey) QWERTY layout
149x67x13 mm, 200g
Completely sealed
Can also be worn on wrist
USB and PS/2 available
Backlighting available
$300-$600 depending on model!
Layout not quite kosher, only 40 keys
(XyberKey offers 60-key version)
Still the winner in the QWERTY category
HandyKeyTwiddler 2 ~140x40x40mm, ~110g
Designed for wearable use
IBM Trackpoint mouse integrated
KB/mouse through PS/2
Chording keyboard The best chording solution by far
Name Pros Cons Assessment
eHolster harness Concealable under coat, blazer, etc.
Harness distributes weight evenly
Available in kinky leather or functional nylon
Expandable and modifiable
Cables can be run on harness straps
Allows component-level mods while wearing it
Impractical in hot weather
Looks seriously bizarre if revealed
Difficult to take on and off
Still the best choice by far!
eHolster eBeltPouch Everything mounts on belt instead
(More) usable in hot weather
Impractical for larger devices
Poor weight distribution
Higher likelihood of banging into things
No place for speakers or some cables
The gear is still too big to make this practical
Sling-type pack (eg. YakPak Tech Sling) Everything nicely packed into one bag
Easy to take on and off
Requires carrying bag around
Not practical when eg. sitting in chair
Turning on/off and accessing modules cumbersome
This approach tried with Yak-1, too many cons


Now add up all the luvverly cyan boxes and proceed to the final design specifications!