- most of what they're using barcodes for could be done just as easily
by typing four-digit codes on the phone keyboard.
Presumably a barcode can use all 10000 symbols, but manual entry would
require some redundancy to catch fat-fingering of fields.
- It might be feasible to put actual applications into a barcode rather
than just field identifiers. PDF-417 barcodes can hold several
kilobytes of data --- I think up to 6 or so.
Not closer to 1K, especially with ECC enabled?
QR code claims to get up to almost 3K:
http://www.denso-wave.com/qrcode/qrfeature-e.html
One nice thing about 2D vs. 1D is that the payload will increase with
the area, but the overhead to recover boundary-sync information can be
limited to increasing with the perimeter.
(off on a tangent:
http://sigfpe.blogspot.com/2006/08/what-can-we-measure-part-i.html)
(I paid bills today and noticed DataMatrices on some of the "receipt
stub" portions, which keep their sync tracks along two of the four
sides)
Similarly, for data-entry applications, you could use barcodes to
tell the cellphone which parts of the paper had which meanings ...
Xerox had a technology about 20 years ago to do exactly that --
although at the time we were interested in it for faxback services and
not cellphones. It should still be around; they show up from time to
time on brokerage statements.
(looks like it's turned into
http://www.parc.com/research/projects/dataglyphs/)
- I think modern inkjet print heads can print at 2100 dpi, and I think
they move across an A-size sheet of paper something like 20 times a
minute
http://www.hackaday.com/2006/10/08/inker-the-hand-inkjet/
One of our Hackaday favorites, [Sprite_tm] made my morning when he
sent this in. He built a driver circuit for a HP inkjet cartridge that
allows him to print by hand. Ideal for printing on other people, their
white boards or their beer. He had to do some blackbox reverse
engineering to figure out what the onboard driver chip does on the
cartridge. Considering the task, the circuit is surprisingly simple.
It has some ATTINY brains, some driver transistors, a data bus and a
DC/DC power converter to get the required 1.21 gigawatts, er 20 volts
to drive the cartridge.
-Dave
