[Kindle Fire HDX 7" & 8.9" Q&A, Help & Troubleshoot] Moronig:
Okay, so I finally managed to solder a working factory cable, and the ot a response from my Kindle Fire HDX 7" (as far as usb is concerned);

Here is the state my HDX is in: If i hold power for 16 seconds, it will start to boot, show the all grey "kindle fire" logo, then the screen turns off.

If I turn it on with the Volume+ button pressed, I get to stock recovery. No amount of factory reset and rebooting will do any good here.

In both cases above, I will get nothing at all on USB when plugged to a computer. No message about it even being plugged in on dmesg.

When I plug in the factory cable, I get a reponse, but a lot of "new high-speed USB device, device descriptor read/64, error -110".

Now here is the interesting part, when I hold power with the factory cable plugged, the device is recognized! Logs will be at the end.

The problem here is I can't get fastboot to show devices. I tried the following:

fastboot devices

fastboot -i 0x1949 devices

fastboot -i 0x05c6 devices

fastboot -s 0 devices

fastboot -s ttyUSB0 devices

fastboot -s /dev/ttyUSB0 devices

And get nothing. I think I am on the right track to getting it to work again, but I'm at a loss about what to do next.

I'm willing to try anything as long as it doesn't involve screwdrivers and/or snakes!

Here is the log from dmesg:

[Ter Dez 3 07:47:10 2013] usb 2-1.2: >new high-speed USB device number 39 using ehci_hcd
[Ter Dez 3 07:47:25 2013] usb 2-1.2: >device descriptor read/64, error -110
[Ter Dez 3 07:47:40 2013] usb 2-1.2: >device descriptor read/64, error -110
[Ter Dez 3 07:47:40 2013] usb 2-1.2: >new high-speed USB device number 40 using ehci_hcd
[Ter Dez 3 07:47:55 2013] usb 2-1.2: >device descriptor read/64, error -110
[Ter Dez 3 07:48:10 2013] usb 2-1.2: >device descriptor read/64, error -110
[Ter Dez 3 07:48:11 2013] usb 2-1.2: >new high-speed USB device number 41 using ehci_hcd
[Ter Dez 3 07:48:21 2013] usb 2-1.2: >device not accepting address 41, error -110
[Ter Dez 3 07:48:21 2013] usb 2-1.2: >new high-speed USB device number 42 using ehci_hcd
[Ter Dez 3 07:48:31 2013] usb 2-1.2: >device not accepting address 42, error -110
[Ter Dez 3 07:48:31 2013] hub 2-1:1.0: >unable to enumerate USB device on port 2
[Ter Dez 3 07:48:42 2013] usb 2-1.2: >new high-speed USB device number 43 using ehci_hcd
[Ter Dez 3 07:48:42 2013] usb 2-1.2: >New USB device found, idVendor=05c6, idProduct=9008
[Ter Dez 3 07:48:42 2013] usb 2-1.2: >New USB device strings: Mfr=1, Product=2, SerialNumber=0
[Ter Dez 3 07:48:42 2013] usb 2-1.2: >Product: QHSUSB__BULK
[Ter Dez 3 07:48:42 2013] usb 2-1.2: >Manufacturer: Qualcomm CDMA Technologies MSM
[Ter Dez 3 07:48:42 2013] usbcore: registered new interface driver usbserial
[Ter Dez 3 07:48:42 2013] usbcore: registered new interface driver usbserial_generic
[Ter Dez 3 07:48:42 2013] USB Serial support registered for generic
[Ter Dez 3 07:48:42 2013] usbserial: USB Serial Driver core
[Ter Dez 3 07:48:42 2013] usbcore: registered new interface driver qcserial
[Ter Dez 3 07:48:42 2013] USB Serial support registered for Qualcomm USB modem
[Ter Dez 3 07:48:42 2013] qcserial 2-1.2:1.0: >Qualcomm USB modem converter detected
[Ter Dez 3 07:48:42 2013] usb 2-1.2: >Qualcomm USB modem converter now attached to ttyUSB0

Here is usb-devices and lsusb output, in case it's needed:

T: Bus=02 Lev=02 Prnt=02 Port=01 Cnt=02 Dev#= 43 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=05c6 ProdID=9008 Rev=00.00
S: Manufacturer=Qualcomm CDMA Technologies MSM
S: Product=QHSUSB__BULK
C: #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=2mA
I: If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=qcserial

Bus 002 Device 051: ID 05c6:9008 Qualcomm, Inc. Gobi Wireless Modem (QDL mode)
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x05c6 Qualcomm, Inc.
idProduct 0x9008 Gobi Wireless Modem (QDL mode)
bcdDevice 0.00
iManufacturer 1 Qualcomm CDMA Technologies MSM
iProduct 2 QHSUSB__BULK
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 32
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 2mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 255 Vendor Specific Subclass
bInterfaceProtocol 255 Vendor Specific Protocol
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Device Status: 0x0000
(Bus Powered)

Thanks!