146 lines
6 KiB
Markdown
146 lines
6 KiB
Markdown
---
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permalink: "/{{ year }}/{{ month }}/{{ day }}/using-a-kindle-for-status-information"
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title: Using a Kindle for status information
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published_date: "2015-05-14 20:50:00 +0200"
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layout: post.liquid
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data:
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route: blog
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---
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Back in 2011 I got a Kindle 4 (the non-touch version) and for some time it was
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the primary device for reading, be it ebooks, technical documentation or slides
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and transcripts from university.
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But then I was using it less and less and for the last one and a half years it basically layed around unused.
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While it is a good device for book reading, it isn't for other content.
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It's slow, it can't handle PDFs properly (zooming is just awful) and adding notes is really annoying with that on-screen keyboard.
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For some time now I have this link saved: [Kindle Weather Display][weather-display].
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Well, what better to do with a lazy holiday then doing some hacking with the Kindle? And so I did and this is the current result: It displays the weather forecast.
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<div style="text-align:center">
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<a href="http://tmp.fnordig.de/kindle/Photo-2015-05-14-19-27.jpg"><img src="//tmp.fnordig.de/kindle/th-Photo-2015-05-14-19-27.jpg" alt="For now it shows the weather forecast"></a>
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</div>
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As the original article is quite short on the precise steps to get this finished, I wanted to write them up here.
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> (Just in case: I'm not responsible if you break your kindle while hacking around with it.)
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First you need to jailbreak your Kindle, this will make the following things a bit easier. You should get it done using this [short guide](http://wiki.mobileread.com/wiki/Kindle4NTHacking#Jailbreak).
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The next step is to set up SSH to get shell access on the Kindle.
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I used the USBnet variant described in the [Kindle 4 NT Hacking Guide](http://wiki.mobileread.com/wiki/Kindle4NTHacking#SSH) (yes, that's the same as the Jailbreak one).
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Despite its name this can enable the SSH daemon on the WiFi interface too.
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Attach the Kindle via USB, mount it and then open the `usbnet/etc/config` and add:
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~~~bash
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K3_WIFI="true"
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~~~
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Now you can also enable auto-starting USBnet. Caution: As long as USBnet is running, you can't mount the Kindle.
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~~~bash
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# the Kindle should be mounted into /mnt/sdb1
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mv /mnt/sdb1/usbnet/DISABLED_auto /mnt/sdb1/usbnet/auto
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~~~
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Next, reboot your device. Once it's back up you should be able to connect to it via SSH on the IP it has in your WiFi network.
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~~~bash
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ssh root@192.168.1.42
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~~~
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The root password is either `mario` or of the form `fionaABCD`. Use the [Kindle root password tool][kindle-password] to find out based on the serial number.
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There's just one more tool: Kite, the application launcher.
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You can get it [in this forum post][kite]. Installation is easy once you got the `kite.gz`.
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Copy the `kite` file to the kindle, then execute it:
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~~~
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jer@brain$ gunzip kite.gz
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jer@brain$ scp kite root@192.168.1.42:/tmp/
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jer@brain$ ssh root@192.168.1.42
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root@kindle# cd /tmp
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root@kindle# chmod +x kite
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root@kindle# ./kite
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~~~
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One thing to note: You just downloaded some binary blob from some random forum and executed it.
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But you did that with the jailbreak and USBnet above anyway.
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And hey, that's how these things worked back in the old days, it actually was totally normal in the [PSP scene](http://fnordig.de/2014/12/03/a-story-of-hacking-or-rust-on-the-psp/) too
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Back to our project: Reboot the Kindle and in the start screen you should see some note that Kite is started as well.
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The Kindle will also contain some new directories:
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~~~
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root@kindle# ls -l /mnt/us/kite
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drwxr-xr-x 2 root root 8192 May 14 12:13 onboot
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drwxr-xr-x 2 root root 8192 May 14 11:57 ondrop
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~~~
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`onboot` is the relevant one. All scripts in there are executed by Kite on startup of the Kindle.
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That's where we disable some stuff and display our image for the first time.
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Write the following code to a file `init-weather.sh` and place it in `onboot` (or [just get it from the repository](https://github.com/badboy/kindle-weather-display/blob/master/kindle/init-weather.sh)):
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~~~bash
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#!/bin/sh
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/etc/init.d/framework stop
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/etc/init.d/powerd stop
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/mnt/us/weather/display-weather.sh
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~~~
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This will disable the framework (= the Kindle UI basically) and the power management daemon (= responsible for disabling WiFi and switching to the screensaver if idle for too long).
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In case you want to get back to the old state, just enable framework and powerd again (and first remove the `init-weather.sh` which will otherwise directly disable them again).
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The `display-weather.sh` script now does the hard stuff, which is pretty easy: Clear the screen, get a new image, display it.
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~~~bash
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#!/bin/sh
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cd "$(dirname "$0")"
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rm -f display.png
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eips -c
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eips -c
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if wget -q http://server/path/to/display.png; then
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eips -g display.png
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else
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eips -g weather-image-error.png
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fi
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~~~
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`eips` is the tool to write something on the screen or display an image.
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Now to regularly and automatically get a new image, set up a cronjob:
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~~~
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root@kindle# mntroot rw
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root@kindle# echo '0 7,19 * * * /mnt/us/weather/display-weather.sh' >> /etc/crontab/root
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root@kindle# mntroot ro
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root@kindle# /etc/init.d/cron restart
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~~~
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The script will now be executed every day at 7:00 and 19:00, showing a picture from the internet (well, at best it's a picture you generated).
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As this post is already getting quite long, I leave the server-side up to you.
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All files (for both the Kindle and the server part) are in the GitHub repository: [kindle-weather-display][repo].
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This is the final result: My Kindle hanging on the wall right under the calendar. :)
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<div style="text-align:center">
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<a href="//tmp.fnordig.de/kindle/th-Photo-2015-05-14-16-44.jpg">
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<img src="//tmp.fnordig.de/kindle/Photo-2015-05-14-16-44.jpg" alt="It's hanging at the wall">
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</a>
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</div>
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[weather-display]: http://mpetroff.net/2012/09/kindle-weather-display/
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[kite]: http://www.mobileread.com/forums/showthread.php?t=168270
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[repo]: https://github.com/badboy/kindle-weather-display
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[kindle-password]: https://www.sven.de/kindle/
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---
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Thanks to [@e2b](https://twitter.com/e2b) for proofreading a draft of this post.
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