On Tue, 2 Feb 2010 06:33:35 +0800
Jaya Kumar [off-list ref] wrote:

You are right, broadsheet is a framebuffer device. It is slightly
different than a typical framebuffer controller that drives a normal
TFT-LCD display. Most E-Ink display panels require a waveform in order
to function. That is, in order to drive the state of a pixel to black,
gray, or white, a specific waveform is utilized. Basically, that
waveform represents the specific E-field wiggling needed to get the
pixel to its optimal state given current temperature, and its previous
state. TN/IPS-LCDs use a similar concept but the driving waveform is
sufficiently simple that it is internalized in the TFT source/gate
driver.

These E-Ink waveforms are specific to a production batch. That is, a
batch of display films are produced, then they get characterized and a
waveform is generated for that batch. Broadsheet, typically, is
attached to its private SPI flash which is then flashed with this
waveform.

Users won't be able to see the waveform and typically won't ever need
to know about it. If however, the display panel attached to broadsheet
is changed out, then they will need to update their waveform. That
would typically be done at a factory or repair facility rather than by
a user.

ah, I'd never have guessed, thanks.  I added that to the changelog ;)