A (commandline based) calendar for Kindle e-readers.
The goal of the projekt is to display a CALDAV-Calendar (from iCloud, nextCloud whatever) as screensaver on your (old) Kindle ebook reader.
All code and scripts are provided as is and comes with no warrenty what so ever.
This litle project is based on two scripts. The show_kahl which goes on a linux-based host system and the get_calendar_image which runs on the Kindle and gets the calander data from the host.
The host is fetching the calendar entries from your CALDAV calendar and creates a png file for the Kindle to download.
This script syncs your caledar entries with vdirsyncer and outputs the calender to the termnial with khal. After that, the output will be captured to HTML with aha and made nice with some CSS. At last the HTML output is converted to a png-image file using chromium and put to the webserver, where it can be picked up by the kindle client.
You need a simple Linux based system as host. I use a Raspberry Pi 2 for example. Basically a similar computer should be fine. Alternativly you can use a Linux-VM or something like that. It should also be possible to run this in a Docker-Container, but I have not tested that as of now.
Also it should not matter if the host runs in your local network or on the internet somewhere. The only thing that matters, is that the host can reach your calendar provider and that it can be reached by the Kindle.
Sync calendar entries with vdirsyncer found here: https://github.com/pimutils/vdirsyncer Show calendar with khal found here: https://github.com/pimutils/khal HTML conversion is done with aha found here: https://github.com/theZiz/aha Conversion from html to png is done with chromium. Any kind of webserver (e.g. nginx),
Make sure you have the apps installed and configured which are listed above. The documentation to khal (and vdirsyncer) can be found here: https://khal.readthedocs.io/en/latest/
When khal is up and running you can copy / checkout the projekt files to your user directory.
On the Host the following files must be installed:
html
aha-footer.tpl
aha-header.tpl
aha-middle.tpl
work
kindlecalendar.conf
show_khal.sh
To export the generated png-file with the calendar events on the kindle, the host needs an active webserver up an running. Depending on the webserver you are goning to use, you need to setup a (virtual) folder called "kindlecalendar".
- Please refer to documentation of your webserver on how to set this up.
When this is done fill out the parameters in the kindlecalendar.conf file:
# Host Adress:
# IP oder DNS name under which the host can be reached in the network
host_server_address="<your_ip_here>"
# Webserver local file path:
# Make sure that the user which executes the show_khal.sh script has read & write permissions on the folders listet below.
# The place in the host file-system where the files are stored for the webserver running on the host device
host_web_server_file_location="/var/www/html"
# Sudirectory for the kindlecalendar files on the webserver
host_webserver_subfolder="kindlecalendar"
If you done that test the script to make sure you have everything set up correctly. You should be able to see your calendar entries in your browser when you run the following adress: /kindlecalendar/output.png (e.g. http://raspberrypi.local/kindlecalendar/output.png).
Keep the browsertab open or note the address somewhere, you will need it below!
To update the calender an a daily basis you need to register the show_khal.sh script in cron.
For that run
crontab -e
add the follwoing line to execute the host script every night an 01:00:
0 1 * * * ~/kindlecalendar/show_khal.sh
The Kindle (the client) now just needs to download the generated png-file and show it as screensaver, while the Kindle is "turned off" / on standby.
The kindle needs to be jailbreaked and the following tools need to be installed: Kindle Screen Saver Hack found here: https://wiki.mobileread.com/wiki/Kindle_Screen_Saver_Hack_for_all_2.x,_3.x_%26_4.x_Kindles Kindle Jailbrake found also in the link provided above USBNetwork found also in the link provided above
Also the KUAL launcher helps to switch the USBNetwork on and off. This is optional, but it can be found here: https://www.mobileread.com/forums/showthread.php?t=203326
Also a good documentation an how to jailbrake the Kindle 4 I am was unsing for the projet can be found here: https://wiki.mobileread.com/wiki/Kindle4NTHacking#Jailbreak
This script picks up the calendar image file from the host´s webserver nd copies it into the screensaver folder.
Plug your Kindle in your computer and create the folloing folders on the Kindle.
kindlecalendar
kindlecalendar/lock
You can create this either in your filebrowser on the desktop or if you are using ssh to log into your kindle (after you have set up USBNetwork) you can use
mkdir /mnt/us/kindlecalendar
mkdir /mnt/us/kindlecalendar/lock
Next copy the following files into the new folder kindlecalendar get_calendar_image.sh kindlecalendar.conf <- this is currently optinal as it is not used yet.
Open the get_calendar_image.sh script and in the curl statement replace the http-address with your host address (from above).
The kindle will only sit there and display the current calendar as its screensaver image. In order to update the calendar the get_calendar_image.sh script needs to run the script periodically. For this a cron job on the Kindle is needed.
To set this up make sure USBNetwork is installed in the Kindle. The to start it either use KUAL or press the keyboard button on the Kindle, and type ;debugOn (make sure to get the semicolon at the beginning), and then enter (↵) to enable debug mode. Press the keyboard button again, and type ~usbNetwork and hit enter (↵). It may pause for a second. Once it’s done, press keyboard, type ;debugOff and hit enter. Reconnect your Kindle to your computer via USB. Connect to you Kindle via SSH using putty on Windows or any terminal on Linux or Mac.
Type ssh [email protected] and hit enter.
You’ll be prompted for a password. The default password is mario.
By default, the Kindle’s drive is mounted in read-only mode. To make it writeable, type mntroot rw and hit enter.
Now you need to edit its configuration file:
nano /etc/crontab/root
Add this line to the bottom
*/5 * * * * /mnt/us/kindlecalendar/get_calendar_image.sh
This checks for a new update every 5 Minutes (see below).
Again, to save and exit type ⌃O, enter, then ⌃X.
Finally, restart cron with /etc/init.d/cron restart
After that log out (with exit) and switch off USBNetwork.
The problem with the Kindle´s sleep mode / standyby mode is, that not much is goning on the Kindle when the screensaver / calendar image is showing. Cron jobs will only be running when the Kindle is "on" -> e.g. the main menu is showing.
So to update the calendar to the current day just turn on the kindle and leave it on the main menu.
After about 5 minutes (or at the time you entered in the crontab root file) the get_calendar_image.sh will run and download a new calendar image and then reboot the Kindle.
When the Kindle falls asleep after the reboot it will show the new calendar image.
The script will only try to download the image and reboot when it did not successfully downloaded a image for the current day.
Try wallmounting your Kindle to have a handy digital calendar wherever you need it. For the Kindle 4 I used this 3d-printed mount from thingiverse: https://www.thingiverse.com/thing:4610302
This is how it looks like:
- improve webserver config
- improve Github documentation
- create a deploy script for the kindle
Credits to MATT HEALY for inspiration! His Kindle projekt can be found here: https://matthealy.com/kindle I also borrowed the guide on how to set up the cronjob on the Kindle mostly from him.