PW 1.8V voltage reference on a PW?

hjalfi · 03-11-2021, 07:08 PM

I have a defunct PaperWhite (probably, the serial number's inaccessible). I'd like to connect up a UART to see if anything comes out and possibly try to get some use out of it that way.

I have the appropriate TTL to USB adapter, but mine requires a 1.8V voltage reference for the low-voltage side (it'll work with any reasonably low voltage). I could try and produce that from my bench power supply but it'd be so much easier if I could source this from the Kindle itself. Before I go poking at test pads to see what comes out, has anyone else managed to figure this out?

Thanks!

hjalfi · 03-12-2021, 05:56 PM

Well, I checked them all and found nothing. There are a number of signal lines but it looks like the 1.8V line isn't exposed on a test pad. I did find a pad which was directly connected to the ~4V battery, and three diodes on that brought the level down to ~2V, but ugh.

Next step: soldering to those horrifying UART pads.

dhdurgee · 03-12-2021, 06:03 PM

Quote:

Originally Posted by hjalfi

Well, I checked them all and found nothing. There are a number of signal lines but it looks like the 1.8V line isn't exposed on a test pad. I did find a pad which was directly connected to the ~4V battery, and three diodes on that brought the level down to ~2V, but ugh.

Next step: soldering to those horrifying UART pads.

Soldering isn't necessary unless you plan to make permanant connections. See threads for alternatives such as pins through sponges, tape, etc.

Dave

hjalfi · 03-13-2021, 02:59 PM

I do need a permanent connection --- the eMMC looks like it's fried! I have a nice setup with a cable coming out of a hole in the back of the machine for the USB adapter now, and it all seems to work. I'm documenting it carefully (on video) and I'll post here once it's all done. Also, wow, soldering these pads was awful.

03-11-2021, 07:08 PM	#1
hjalfi Member Posts: 24 Karma: 10 Join Date: Apr 2011 Device: Kindle 3g	1.8V voltage reference on a PW? I have a defunct PaperWhite (probably, the serial number's inaccessible). I'd like to connect up a UART to see if anything comes out and possibly try to get some use out of it that way. I have the appropriate TTL to USB adapter, but mine requires a 1.8V voltage reference for the low-voltage side (it'll work with any reasonably low voltage). I could try and produce that from my bench power supply but it'd be so much easier if I could source this from the Kindle itself. Before I go poking at test pads to see what comes out, has anyone else managed to figure this out? Thanks!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Aura H2O Vcom voltage changing	m4103	Kobo Developer's Corner	0	09-29-2018 07:51 AM
K3 battery voltage? (I²C details)	Popup	Kindle Developer's Corner	42	10-12-2012 05:05 PM
battery voltage	p3aul	Sony Reader	10	05-01-2010 02:40 AM
PRS-300 Voltage on AC Chargers	Shopaholic	Sony Reader	5	02-04-2010 05:26 PM
Is the PRS Auto-voltage?	orien	Sony Reader	2	05-15-2008 02:48 AM

03-12-2021, 05:56 PM	#2
hjalfi Member Posts: 24 Karma: 10 Join Date: Apr 2011 Device: Kindle 3g	Well, I checked them all and found nothing. There are a number of signal lines but it looks like the 1.8V line isn't exposed on a test pad. I did find a pad which was directly connected to the ~4V battery, and three diodes on that brought the level down to ~2V, but ugh. Next step: soldering to those horrifying UART pads.

03-13-2021, 02:59 PM	#4
hjalfi Member Posts: 24 Karma: 10 Join Date: Apr 2011 Device: Kindle 3g	I do need a permanent connection --- the eMMC looks like it's fried! I have a nice setup with a cable coming out of a hole in the back of the machine for the USB adapter now, and it all seems to work. I'm documenting it carefully (on video) and I'll post here once it's all done. Also, wow, soldering these pads was awful.

Advert