Diptyx E-reader

It's time for another quick software update! In this update, two major functionalities are added, namely pinning books, and unifont fallback for special characters.

Pinning books

In the book library, you can now click on a book with the middle button to add it to your favorites list. This is shown as a small heart underneath the pagecount of the book,. Favorite books are listed under the favorite books tab, which is always the first element in the library menu.

Unifont fallback
Custom proportional fonts are supported in the .yaff format. These fonts often do not support non-european characters such as Chinese or Korean however. In this update, a fallback in Unifont is implemented: Characters that are not supported in the currently selected font are rendered in Unifont instead, this can be the case for normal characters, but also special characters like emojis for example.

I am excited to announce that the the crowdfunding campaign for the Diptyx E-reader has officially started!

I have been quite intrigued by the idea of using the Diptyx E-reader as a platform for writing/note taking. The screens that I'm using have a update time of about 0.8s, with a custom LUT. In practice this means that the displays will start updating practically instantly, but takes 0.8s to finish updating, blocking any  new data from being displayed in the mean time. It is possible to shorten this duration, but this then decreases the contrast of what is being displayed..

So that's where I got the idea: Instead of updating the pixels in a single refresh, we update each pixel in multiple quick updates. In this way, we get good responsiveness, but also good contrast. 
We have 2 framebuffers, in these we store the target levels for each pixels (0 for white, 10 for black), and the current level. Now, for each frame we check if the level of each pixel is lower or higher than the target level. If this is the case, we update that pixel on the screen, and add or subtract 1 to the current level of that pixel. 
If we now set the target level of pixel to 10, the pixel will receive 10 short updates in the next 10 frames, and will then be left in neutral. (this btw makes it also possible to use grayscales, simply by setting a lower target level! )

In the video you can see a quick demo of what typing looks like with this technique:

With the two screens you could do some very cool things, like writing markdown in the left screen, and seeing the rendered text in the right screen. Or imagine a text adventure with the text interface in the top screen, and a view  of the map or inventory on the bottom screen. 

When reading with the Diptyx E-reader, you can add a bookmark to the current page by pressing the down button. This shows a black triangle in the top-right (like folding the corner of a page in a real book), and you can quickly jump to a bookmark in the quickmenu. 
There is an issue with this however: When changing the rendering settings (font, font size, line-spacing, etc.), the layout of the book changes, and the book must be re-indexed. This changes what text is displayed on which page, meaning the bookmarks are now useless!

In the latest software update, this has now been resolved. Instead of only saving the pagenumber of each bookmark, we now also store the chapter in which the bookmark is present, and the index of the first html element on the page that the bookmark points to. Now, when re-indexing the book after changing the render settings, the book indexing routine will check for every html element that it comes accross if the bookmark is present there, and change the pagenumber of the bookmark accordingly. 
There can always be a slight discrepancy, as the contents of each page is slightly different when changing the render-settings, but even in the worst case the bookmark likely won't be off by more than a page after re-indexing.

To further customize your reading experience, I have added the functionality to choose the type of idle screen you want. By default, when the device enters stand-by or is manually shut down, the screens remain the same, except for a small notification in the lower-left corner indicating whether the device is in deep sleep or fully off.

Now, in the settings menu there is a new setting, called standby screen, which can be set to 'none', 'current book', or 'custom'. When set to none, the previous behavior remains. When set to current book, the cover of the book that you're currently reading is displayed:

And finally, when set to custom, two images are displayed on both screens. These images are stored on the SD card, and can be easily changed by uploading new images through the usb port: