Mobileread
Get rid of Kindle Paperwhite's backlight
#1  joblack 12-22-2012, 12:23 PM
If you're like me you like the higher resolution of the Kindle Paperwhite but hate that it isn't possible to turn the backlight off. The hint to the system device name came from another forum user so thanks for it.

What do you need?

- Jailbroken Kindle Paperwhite (check the other howtos in this forum section)
- Installed USB Network Hack
- USB cable
- Putty (or any other ssh client)
- Linux (or Windows with USBNet driver)
- Make sure you know a little bit about Linux command so you won't accidentally delete your Kindle root partition. And of course no guarantee from my side.
  1. SSH to your Kindle PW
  2. mntroot rw
  3. vi /etc/crontab/root
  4. press i to go into the insert mode
  5. add the following lines to the file
    Code
    # get rid of the nerve ranking backlight
    * * * * * /bin/echo -n 0 > /sys/devices/system/fl_tps6116x/fl_tps6116x0/fl_intensity
  6. save the file (with :x)
  7. mntroot ro

Reboot the device. That's it. After most after a minute uptime your backlight is off. If you enabled it again (woke the Kindle up?) you just need to wait another 60 seconds (you can already use the Kindle PW - it will be disabled).

I haven't found a way to include this in the GUI or change the default values for the backlight. Maybe somebody has an idea where to find it (I suspect it's hidden somewhere in the JAR files).

The disadvantages of this 'quick and dirty' approach is that you can't enable the lighting again without changing the cron file and maybe your Kindle needs a little bit more energy.
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#2  hawhill 12-22-2012, 12:49 PM
Hm, did you check how much energy it consumes? It will run every minute, even when in standby and lying on the shelf... I would consider it risky, I guess.

Then anybody who wants to do it should probably
a) be aware of the risks, but you wrote that in your guide
b) know "vi" (heh, that's a clever move to keep the newbs away :-P ) - but then there may be other options,
c) do backups. DO BACKUPS!
d) add in step 7: mntroot ro

And I guess this thread belongs into the developer's board.
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#3  joblack 12-22-2012, 12:57 PM
Quote hawhill
Hm, did you check how much energy it consumes? It will run every minute, even when in standby and lying on the shelf... I would consider it risky, I guess.

And I guess this thread belongs into the developer's board.
No I haven't. I created the patch just an hour ago. So far it's working.

Maybe it will consume more energy, maybe less (the light is off so that counts for something). There are other entries in the crontab file (which run every 15 minutes) and the cpu frequency governor is set up to 'ondemand' so IMHO it won't eat much of your energy.

Yes it should be in the dev section but I know of no way to move it. Maybe a moderator can move it? Thanks.
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#4  joblack 12-23-2012, 05:05 PM
After a day of testing I can say:

- it works fine
- energy usage isn't more than before
- no 'bricking' ...
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#5  HarryT 12-24-2012, 03:51 AM
Allow me to point out that the PW doesn't have a "backlight". No eInk screen can be backlit, for the very simple reason that the screen is opaque. Even a glance at a PW should show you that it's frontlit - the LEDs which provide the lighting are clearly visible.

As developers, I think it's important to get these things right!
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#6  siejas 12-25-2012, 02:07 PM
Hi!

joblack, thanks for the hack! Worked flawlessly. Great idea based on what geekmaster did here.

Still, there was quite a drawback - once you put lighting off in cron, you won't be able to easily turn it on again (at least for more than a minute). Therefore I propose other solution:

Code
* * * * * var=$(cat /sys/devices/system/fl_tps6116x/fl_tps6116x0/fl_intensity | grep -e '[0-9]'); if [ "$var" = "FrontLight(Intensity) = 1" ]; then echo -n 0 > /sys/devices/system/fl_tps6116x/fl_tps6116x0/fl_intensity; fi
Simply put it in crontable instead of joblack's code. Every minute it checks if the lighting is in the lowest setting available by kindle interface and if so, it turns the light off completely. But it won't do anything if the setting is other than the lowest. So you can easily use PW both with and without light with no need of further changes in crontable.
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#7  HarryT 12-25-2012, 03:21 PM
Is there really any point in this? If you're in an environment in which you can read the PW's screen unlit, you're not (in my experience) going to see the slightest difference between the light being off, and being on its lowest setting of "1".
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#8  siejas 12-25-2012, 03:42 PM
Well, that's a decent point. Frankly, I do agree with you, there is not much difference.

However, a friend of mine was about to return his PW just because he was so upset not being able to turn the lighting off completely. I've applied the hack on his demand and it worked fine, so I believe there is a small number of PW users that for various reasons consider it a really huge issue. It might not be my case, but still.

So I don't recommend going through all those steps including jailbreaking your device and setting up usbnet if you aren't absolutely sure this is exactly what you need. But if you do, I'm glad to help!
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#9  centhena 12-26-2012, 11:30 PM
Just to throw my 2 cents in. I would absolutely LOVE the ability to easily turn the light completely off and back on at my leisure. It was the first thing I noticed when I got my new paperwhite and it was a disappointment. After years with my old Kindle, I do notice the difference, so your work on this is not without a grateful audience.
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#10  joblack 12-27-2012, 01:53 PM
Quote HarryT
Allow me to point out that the PW doesn't have a "backlight". No eInk screen can be backlit, for the very simple reason that the screen is opaque. Even a glance at a PW should show you that it's frontlit - the LEDs which provide the lighting are clearly visible.

As developers, I think it's important to get these things right!
Yeah, yeah I know it's not a real back light but it's close enough. You'll get the official smartass award.
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