NanoNotes and electronic dictionaries

Werner Almesberger werner at almesberger.net
Fri Aug 23 18:41:13 EDT 2013


Paul Boddie wrote:
> I imagine that one significantly different thing is the keyboard.

I'd consider the keyboard the most difficult component. My
hardware difficulty ranking would be, from hardest to easiest:

1) keyboard
2) case
3) WLAN
4) LCD
5) battery
6) audio
7) CPU and all the rest

The ideal keyboard would not only work and "feel right" but it would
also allow for relatively easy reconfiguration. E.g., by accepting
keycaps or similar that can be manufactured or imprinted with a
small-tech approach (CNC mill, 3D printer, laser cutter, etc.)
suitable for low-volume customization.

Note that there are quite unusual approaches that work well. E.g.,
the OQO 01/01+ had a keyboard with small round buttons under a
plastic film. Unlike the Sinclair ZX80/81, which used a somewhat
similar approach, with painful results, the OQO keys had very clear
tactile feedback.

> Looking at screens, it seems pretty difficult to get one the same size as the 
> Ben's.

Maybe not: go to http://www.ampire.com.tw then click on "TFT" in the
side bar. The AM320480B looks quite reasonable for the Ben form
factor: module size 87 x 58 mm, 480 x 320 pixels, 3.5" diagonal, 164
dpi, 3:2 aspect ratio. This seems to be very similar to the iPhone 1
and 3 display, so there ought to be a gazillion more.

For comparison, the Ben's display: 70 x 51 mm, 320 x 240 pixels,
3.0" diagonal, 133 dpi, 4:3 aspect ratio.

They're probably not too hard to source in the Chinese market.
There are also some EU distributors that list it. Fun feature: the
controller has its own frame buffer, so the CPU could stop screen
refreshes when there are no changes and thus have more memory
bandwidth available for other things.

Data sheet of the "A" version of that display:
http://gamma.spb.ru/download/AM-320480ATMQW-B0H.PDF
http://www.ampdisplay.com/documents/pdf/AM-320480A1TZQW-TB0H.pdf

The controller (RM68040) appears to be the same as the Ilitek
ILI9481, with this data sheet:
http://www.allshore.com/pdf/ILITEKILI9481.pdf

> What is interesting about the Ben is that the screen only takes up 75% 
> or so of the available space, which then makes one wonder whether the case 
> could accommodate a larger panel anyway.

Yes, there's a lot of unused space there. Just about as much as the
above larger display would fill. This is what a scan of the Ben's
display frame looks like:

http://projects.qi-hardware.com/index.php/p/ben-scans/source/tree/master/data/jpg/ben-lcdframe-front-500um.jpg

This display is slightly asymmetric, so a symmetric placement would
leave room for an RF cable on one side leading to an antenna in the
top area of the display shell.

- Werner



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