K4 Is it possible to change the image displayed for drained battery?

generalheed · 10-08-2022, 03:41 AM

Just dusted off my old Kindle 4 from 10 years ago and decided to finally get some use out of it by jailbreaking it. I'm thinking of turning it into a digital photo frame and I've seen some projects for that already too. But what I'm curious about is if it's possible to change the system image displayed for when the battery is dead? So instead of displaying the charge battery image, I can have it permanently display another image until I charge it again? That way it can be used as a permanent picture frame even if the battery is totally drained.

Not sure if it's a simple image file swap somewhere in the directories or if I have to compile a whole new custom OS, but any insight would be much appreciated!

Aleron Ives · 10-08-2022, 04:16 AM

Although I can't answer that specific question, I think it's important to note that leaving the battery at 0% will rapidly destroy it and render the Kindle unusable in the future. Lithium-ion batteries dislike states of extreme charge and discharge. If you want to leave it off for a long time, you should discharge the battery to around 50% and then turn it off.

guoyongzhi · 10-08-2022, 07:08 AM

/usr/share/blanket/shutdown/bg_critbatt.png

NiLuJe · 10-08-2022, 06:04 PM

Keep in mind that upsetting blanket by screwing this up is probably a very good way to soft-brick a device ;o).

generalheed · 10-08-2022, 10:01 PM

Quote:

Originally Posted by guoyongzhi

/usr/share/blanket/shutdown/bg_critbatt.png

Hmm the blanket directory doesn't seem to exist in /usr/share for me.

NiLuJe · 10-08-2022, 11:32 PM

Oh, right, blanket is a FW 5.x daemon

.

I... don't remember how it worked before ;o).

There's quite likely either a PNG or a framebuffer dump *somewhere*, though.

generalheed · 10-09-2022, 02:26 AM

Quote:

Originally Posted by NiLuJe

Oh, right, blanket is a FW 5.x daemon

.

I... don't remember how it worked before ;o).

There's quite likely either a PNG or a framebuffer dump *somewhere*, though.

Ahhh I found it, it's stored at:

./opt/amazon/low_level_screens/600x800/critbatt.png

Now before I make changes to these images, do I need to watch out for anything to prevent bricking my Kindle?

NiLuJe · 10-09-2022, 01:16 PM

Double-check the *exact* encoding peculiarities of the PNG.

It's likely to be a true PNG8 with a full 256c palette (i.e., -define png:color-type=0 -define png:bit-depth=8 for ImageMagick).

10-08-2022, 03:41 AM	#1
generalheed Junior Member Posts: 3 Karma: 10 Join Date: Oct 2022 Device: Kindle 4	Is it possible to change the image displayed for drained battery? Just dusted off my old Kindle 4 from 10 years ago and decided to finally get some use out of it by jailbreaking it. I'm thinking of turning it into a digital photo frame and I've seen some projects for that already too. But what I'm curious about is if it's possible to change the system image displayed for when the battery is dead? So instead of displaying the charge battery image, I can have it permanently display another image until I charge it again? That way it can be used as a permanent picture frame even if the battery is totally drained. Not sure if it's a simple image file swap somewhere in the directories or if I have to compile a whole new custom OS, but any insight would be much appreciated!

10-09-2022, 01:16 PM	#8
NiLuJe BLAM! Posts: 13,484 Karma: 26012494 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w, PW, PW2, PW5; Kobo H2O, Forma, Elipsa, Sage, C2E	Double-check the exact encoding peculiarities of the PNG. It's likely to be a true PNG8 with a full 256c palette (i.e., -define png:color-type=0 -define png:bit-depth=8 for ImageMagick). Last edited by NiLuJe; 10-09-2022 at 01:18 PM.

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10-08-2022, 04:16 AM	#2
Aleron Ives Wizard Posts: 1,191 Karma: 15499944 Join Date: Sep 2022 Device: Kobo Libra 2	Although I can't answer that specific question, I think it's important to note that leaving the battery at 0% will rapidly destroy it and render the Kindle unusable in the future. Lithium-ion batteries dislike states of extreme charge and discharge. If you want to leave it off for a long time, you should discharge the battery to around 50% and then turn it off.

10-08-2022, 07:08 AM	#3
guoyongzhi Member Posts: 19 Karma: 3094 Join Date: Sep 2021 Device: KOA2	/usr/share/blanket/shutdown/bg_critbatt.png

10-08-2022, 06:04 PM	#4
NiLuJe BLAM! Posts: 13,484 Karma: 26012494 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w, PW, PW2, PW5; Kobo H2O, Forma, Elipsa, Sage, C2E	Keep in mind that upsetting blanket by screwing this up is probably a very good way to soft-brick a device ;o).

10-08-2022, 11:32 PM	#6
NiLuJe BLAM! Posts: 13,484 Karma: 26012494 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w, PW, PW2, PW5; Kobo H2O, Forma, Elipsa, Sage, C2E	Oh, right, blanket is a FW 5.x daemon . I... don't remember how it worked before ;o). There's quite likely either a PNG or a framebuffer dump somewhere, though.

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