project idea: portable password safe

Paul Boddie paul at
Tue Sep 10 17:54:00 EDT 2013

On Tuesday 10. September 2013 22.38.23 Werner Almesberger wrote:
> Paul Boddie wrote:
> > I added a project involving e-paper to the wiki:
> > 
> >
> Nice ! How is the contrast for text ? In the pictures, the contrast
> looks low, but that may be just because of the content.

The Pervasive Displays site provides some reasonable (in other words: not 
completely faked) illustrations:

(That saves me the effort of getting the panel back out and doing some tests!)

The limitation of these screens is the resolution. As you can see, you have to 
go as far up as the 10.2" panel at the top of the range to get a pitch 
(160dpi) that people would consider for an e-reader. Meanwhile, the contrast 
is fairly reasonable and it obviously gets better in bright light (unlike 
LCDs), although I don't make use of the temperature sensor with the Ben and 
consequently perhaps don't give each pixel enough time to saturate under 
certain conditions.

As one can conclude from the above site, these panels are intended for 
signage, either for store shelf pricing or for things like museum exhibits. I 
think it has been at least two or three years since a supermarket situated at 
my former employer introduced electronic shelf labels throughout the store, 
including in the refrigerated section (thus testing their capabilities 
further), so I imagine it's a market set to grow in the coming years.

Here's the Adafruit version of the solution:

I think the "upstream" code from my vendor's solution is now bloated with lots 
of extra graphical library stuff from Adafruit's version, at least for one of 
the supported boards, meaning that one has to sift through lots of irrelevant 
files to figure out what is actually needed to support the panel on different 
hardware to that already supported - the curse of microcontroller accessory 
projects, I guess - and I think most vendors have added flash memory to their 
boards for the benefit of Arduino, which is then used to complicate matters 

Still, I intend to come back to this with some ideas of putting it to 
appropriate use.


More information about the discussion mailing list