inspired by the barcode CAMBrowser

[Dave Long]

> - 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