05-01-2016, 10:40 AM | #1 |
Bit Wrangler
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Investigating the Kindle Oasis
Since I did not want to wait for somebody tearing down the Kindle Oasis anymore I decided to open up mine. The Cover uses double sided tape to fix the cover to the back so one cannot take apart the oasis too often without replacing it. otherwise the disassembly is fairly easy but be aware that the plastic noses that hold the cover attached towards the thicker part of the case are not really angled correctly for being detached damage-free too often.
No serial port pins seem to stand out but there are quite a few testpoints that have a voltage between 2.5v and 1.6v fitting an active serial pin. I could figure out a few of the pins on the backcover connector. the left and rightmost pins are GND and case-ground and the second leftmost carries VBat the two remaining pins seem to be a i2c bus for the cover. |
05-01-2016, 12:02 PM | #2 |
BLAM!
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Yeah, given the size of the board, I was afraid serial was going to be a thing of the past... :/.
Thanks for the early look, though . |
05-01-2016, 12:18 PM | #3 |
Sir Penguin of Edinburgh
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Thanks for posting the photos!
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05-01-2016, 12:40 PM | #4 |
Carpe diem, c'est la vie.
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If no serial, it may have JTAG (for initial factory programming). A bit more difficult, but there are plenty of DIY solutions for that too, some of which may be adaptable to kindles:
HairyDairyMaid JTAG Debrick Utility When somebody bricks one of these new kindles, it may be worth trying the JTAG debricking methods. Another MUCH LESS SAFE approach would be the "pin shorting" method, to make the device think it has corrupt flash, so it reverts to device firmware update (DFU or TFTP) mode: Bricked Linksys WRT54G repair instructions Something similar may work on some kindle devices for which there is no other approach, and you cannot return it to amazon for a replacement (though only as a last resort due to risk of hardware damage). I debricked plenty of routers that way (before safer methods were developed), though a kindle Oasis is a bit expensive to take pin-shorting casually -- JTAG is worth the extra effort if this kindle model supports it (though TTL serial and USB are the simplest basic debricking interfaces, if we can find out how and where). Last edited by geekmaster; 05-01-2016 at 12:57 PM. |
05-01-2016, 08:33 PM | #5 |
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Serial Interfaces are still included in every SOC chip as a standard. It is surely used during development. The question really is how Amazon chose to make it accessible.
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05-01-2016, 08:37 PM | #6 |
Going Viral
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Time to try the 'factory USB adapter' -
The one used with the color Kindles. They almost have to have serial port or its equivalent access or the devices are useless in the re-cycle/re-furbish market. |
05-01-2016, 08:43 PM | #7 | |
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Quote:
Also traditional Bootloader access isn't possible with this. My bet is that there are serial pins one one of the ZIF sockets that need a special development cable or alternatively that there is a "magic" pin combination for the battery connector after all. Last edited by blkhawk; 05-01-2016 at 08:48 PM. |
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05-01-2016, 08:46 PM | #8 | |
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Quote:
P.S: Android is also run by a Linux kernel, (with the exception of one system call) it is only user-land that is different. |
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05-01-2016, 08:52 PM | #9 | |
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Quote:
There is a provisioning system that works over USB for the Kindle without a doubt. But I would bet that it just uses the Update system. I don't think it deals with truly "bricked" devices. |
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05-01-2016, 09:03 PM | #10 |
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During boot the oasis like other kindles only offers USB Storage. There is no hint at a special USB device like you would see with most Android devices.
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05-01-2016, 09:31 PM | #11 | |
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Quote:
If not, you will not and should not, see any hint of any other device. Take a close look at the micro-usb connector - see that it has 5 pins, not 4? That fifth pin controls what functions will be seen over the cable. |
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05-02-2016, 03:55 AM | #12 |
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Well theoretically yes - however this would only apply fairly late in the boot process since you need active monitoring of the resistance to that pin to select different modes for it. In development you usually need access right in the boot loader. That means in practice that a device would at first show up with a special USB device id - it defaults to the "development device" (for Android devices this is FASTBOOT) then when the kernel start to load it "unplugs" then replugs with the normal production dev id. After this point "Magic" cables might switch different modes. I think a early-boot magic cable is fairly unlikely for the kindle.
A usbnetwork activating cable is a possibility - I might investigate this with a decade-resistor and microusb-breakout board. |
05-02-2016, 05:15 AM | #13 | |
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Quote:
I posted the i.MX6 reference manual somewhere around here. Try reading it. 10 10 1 Last edited by knc1; 05-02-2016 at 05:22 AM. |
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05-31-2016, 05:38 AM | #14 |
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Some Updates
Still no Serial JB for the Oasis but I thought I should document what I tried so far to prevent double efforts by others.
I combed the board for test points with a serial signal on them and found a group of pins that I could have sworn was the right one (see attached picture). The grouping of 4 pins shows the typical VCC and GND on 2 of the 4 pins as well a logic-level voltages on the other 2 pins. Since there is a small chance I messed up attaching the leads (the pins are fairly small) I will retry the procedure later. I also tried to find a factory-cable function by building a decade-resistor and attaching it to the usb-id pin on the microusb plug. A range of resistor values in 1 and 5 increments between 1MOhms and 100Ohms in both pullup and pulldown with device reboots and usb plug events produced no definitive reaction from the device. I had more reaction in the pulldown than with the pullup tests (loss of usb storage connectivity in one test) so somebody might have more luck there. Since it wasn't repeatable it might have been a fluke. Has anyone else experimented with the Oasis and can maybe share some experiences? |
05-31-2016, 08:00 AM | #15 |
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Would you please post a picture (or pictures) of the other side of the board?
The first post is two pictures of the same side of the board. Ah... And don't forget to examine closely the cover connectors - - They may have used those to also carry the serial port connections, similar to the K3. |
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