Ya: backlit keyboard - Rii Mini case study
werner at openmoko.org
Tue Jul 13 12:39:16 EDT 2010
Wolfgang Spraul wrote:
> good to see how others solved the backlight problem.
I was afraid that there would be just a few LEDs but a lot of
"fancy plastic" to distribute the light. It's nice that what
seems to be a much more pedestrian approach works so well.
> Does this have anything to do with 'USB'? First time I hear about WirelessUSB.
> Wikipedia says WirelessUSB operates at 3.1 to 10.6 GHz, but the Cypress chip
> talks about 2.4 GHz?
The difference may be in the space between "Wireless" and "USB".
Without it, it's Cypress' 2.4 GHz stuff, about which they proudly
| WirelessUSB and enCoRe are trademarks of Cypress Semiconductor.
The Wiki page says that USB-IF prefers people to call theirs
somewhat pompously "Certified Wireless USB". I guess now we know
A good comparison:
http://www.ac.tut.fi/aci/courses/ACI-31070/pdf/UWB WUSB WirelessUSB.pdf
> Maybe to look at RF in Ya, we should first identify some interesting, free
> software / GPL licensed stacks? Then find a matching module/RF IC for it?
I'm still not sure what would be the best strategy. I've tried a
search for standards (see below) but I'm not entirely happy with
the results. I've now started to look at what the major chip
makers have to offer.
> Are you aware of any good and stable RF protocol stacks implemented in
> free software?
Nothing interesting beyond things that have already been mentioned.
I would in fact go one step back and look for Open standards, not
Here's a very rough compilation of things I found so far for the
ISM bands that aren't flat out "vendor standards":
Band Rb Range Modulation Openness/Patents Ref.
434 915 kbps m Standard Use
| 868 2.4 (nom)
| | | |
Wibree - - - x 1000 10 ? "open" ? 
IEEE 802.15.4 - x x x 20-250 ? many open  ? 
6LoWPAN n/a n/a n/a n/a open  open? 
MiWi - - - x -250 ? ? unpublished ? 
WirelessHART - - - x ? ? QPSK for-pay roylty-free 
ZigBee - - - x 250-500 75 QPSK 
INSTEON - - x - ? 50 FSK for-pay? ? 
ISO/IEC 18000-7 for-pay? RAND 
DASH7 x - - - 28-100 250 FSK,GFSK = = 
ONE-NET ? x x ? ? ? FSK ? roylty-free 
Wavenis x x x - 5-100 100+ ? ? ? 
Wireless USB > 3 GHz 53-480 10 MD-OFDM open  ? 
Z-Wave - x x - 10- 40 30 GFSK NDA ? 
(Site requires registration and moderator approval to even read any
(links to IEEE standard documents, with click-through license)
note: 802.15.4-2006 specifies ASK for 868/915 but requires devices to also
http://ww1.microchip.com/downloads/en/AppNotes/MiWi Application Note_AN1066.pdf
Implementation tied to use of Microchip products. No indication about IP
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