Navigable Dashboard on Kindle 4

Some time ago at the dormitory, we wanted a common display to have the current weather, personal quotes, and other information be viewable at a glance in the kitchen. This means some display has to receive regular updates. E-paper displays are pre-destined to fulfill the use case, as they just use power on redraws and do not emit light, unlike common LED displays. Also, they are pleasant to look at in my opinion. There is, however, one drawback, such that e-paper displays larger than 25 inches are currently very expensive. So you have to resort to smaller displays and work around the limited space.

E-paper displays around 6 to 10 inches available for consumers can be more expensive than buying a used e-book reader of the same size. In this case we choose a used Kindle (4th generation) with a 6-inch display. On such a 600x800 pixel display, you need to find the balance between information density and content size, which determines the possible viewing distance.

In our use case, some information should always be large and well visible. Other information can be switched on-demand using the Kindle navigation buttons. Kindles cannot render web pages sufficiently fast, such that the rendering is outsourced to a server. This works similarly to kindle-dash from pascalw, but it allows you to navigate between multiple pages and does not enter low-power mode. Additionally, the Kindle rotates between the pages hourly.

Energy consumption-wise, it can run for a few days on battery. The most draining aspect is the permanent wifi connection, which you could power only on demand. But it would not last for a year, and a more long-term solution is to keep it plugged in all-the-time here.

Dashboard Setup

This component is a bit resource-heavy because it takes screenshots from your custom webpage with a headless Chrome instance using Puppeteer, but in the end it is a working method to create your 600x800 pixel images for the Kindle display. The dashboard consists of a node server using express and handlebar templating for your pages. I did not want to interact much with the Kindle setup, so it also provides endpoints for the latest viewed page and total page count, in case it changes in the future.

You can clone the kindle4-navigable-dash repository.

For local development you can run:

cd node_server
npm install
npm run server

and view the current page on localhost:45700.

A page has a common header with the current weather and a small footer to see the previous and next page. Inside node_server/views/ you can modify and design your pages. To add it, modify PAGES in node_server/server.mjs accordingly. The array index determines the page number. The weather is fetched via the OpenWeather API, which requires a provided API key and city. Create a .env with your OW_API_KEY and OW_CITY variables. Also, every time the current page number /current is requested by the Kindle, the server updates the variable to a new page, such that on the next request the Kindle shows a different one. If you are happy with your customizations, you can deploy it with Docker:

docker build --tag kindle-navigable-dash .
docker run --env-file .env -p 45700:45700 kindle-navigable-dash:latest

In the end, you can access a page <YOUR IP>:45700/page/<PAGE_NUMBER> and get a grayscale image in Kindle format via /screenshot/page/<PAGE_NUMBER>.

Kindle Configuration

Jailbreak

At first you need to jailbreak the Kindle, and then you can set up SSH access. You can connect over USB, and then you can set up your WiFi connection if you refer to the USBNet README. Additionally, the Python package has to be installed, available from this forum post.

Setup Kindle

After you can connect to your Kindle with the default password from the wiki:

ssh root@KINDLE_IP

You can remount the filesystem to read-write to copy the scripts:

mntroot rw

Then the scripts from the same repository need to be copied:

scp ./kindle/* /mnt/us/

The Python script reacts to key presses and displays different pages, which are saved in /tmp. These pages need to be first downloaded from the web server, done by the update_screens.sh script.

Add the following two lines to /etc/crontab/root for hourly page updates:

@reboot /mnt/us/setup_screens.sh
0 */1 * * * /mnt/us/update_screens.sh

The @reboot directive does not seem to really work, but the following modification in /etc/rc.d/functions disables the default Kindle reader startup and chooses our own script instead. Find the line with START_FRAMEWORK= and change it to:

START_FRAMEWORK=/mnt/us/setup_screens.sh

To start directly without a reboot, run:

/mnt/us/setup_screens.sh
/mnt/us/update_screens.sh

Now you should have everything set up and can use the navigation buttons to select the next and previous pages.

Hopefully we can see some larger, commercially viable e-paper displays in the future, but until now, e-book readers provide a neat solution.