Updated my Flo to the latest versions of Unlegacy Android, TWRP and Magisk a while ago. Afterwards, it wouldn't charge. The USB settings behaved somewhat flaky too, so decided to go back to the earlier versions. Still wouldn't work. Noticed at that point that it wouldn't charge in TWRP either (it should, right?). Decided to try to flash the latest stock rom to rule out any software problems. Put the Flo in bootloader mode, where Fastboot wouldn't find it, no matter which USB port and cables I tried. Tried to reflash the bootloader instead, should rule out any software related problems too.
I've loaded up USBTreeview on the computer to monitor USB activity, and tried plugging the Flo in different USB modes. Nothing happens at all, the USB port seems completely dead.
Also opened the Flo up, stripped a USB Micro cable, and tested for continuity between the wire ends and points after the connector on the PCB. The connector turned out to be ok.
The strange thing is that it charges just fine if I turn it off completely. Assuming it has something to do with everything that could control the charging circuitry being turned off.
So, anyone got any ideas at all what to try next? I'm out of them myself.
.kaputnik. said:
....stripped a USB Micro cable, and tested for continuity between the wire ends and points after the connector on the PCB. The connector turned out to be ok....
Click to expand...
Click to collapse
If you refer to the daughterboard PCB then it is inconclusive. Continuity between the port and the motherboard PCB needs to be verified. The wide, silver cable between the PCBs is often problematic. The connections are....
A - 1 (+5V)
B - 3 (data)
C - 2 (data)
D - 4 (OTG)
E - 5 (GND)
k23m said:
If you refer to the daughterboard PCB then it is inconclusive. Continuity between the port and the motherboard PCB needs to be verified. The wide, silver cable between the PCBs is often problematic. The connections are....
A - 1 (+5V)
B - 3 (data)
C - 2 (data)
D - 4 (OTG)
E - 5 (GND)
Click to expand...
Click to collapse
Thanks for the suggestion
Checked the connections as per above, had continuity between all testpoints. The silvery FFC and its connectors seems to be fine.
Also pulled and reseated the FFC in both ends, just in case temporary contact was made somewhere when I removed and flipped the motherboard over to access the test points. No change though, the USB port is still dead
Edit: you don't happen to know what the 4 pin surface mount IC on the data traces close to the USB connector is? Two diodes integrated on an IC perhaps?
.kaputnik. said:
Thanks for the suggestion
Checked the connections as per above, had continuity between all testpoints. The silvery FFC and its connectors seems to be fine.
Also pulled and reseated the FFC in both ends, just in case temporary contact was made somewhere when I removed and flipped the motherboard over to access the test points. No change though, the USB port is still dead
Edit: you don't happen to know what the 4 pin surface mount IC on the data traces close to the USB connector is? Two diodes integrated on an IC perhaps?
Click to expand...
Click to collapse
I checked N7's USB port....
Unit off, charger disconnected, ohmmeter measures:
GND-5V: 8kohm
GND-D1: 3Mohm
GND-D2: 3Mohm
D1-D2: 8Mohm
(meter polarity makes no difference)
Unit on, Android running, voltmeter measures:
GND-5V: 0V
GND-D1: 0V
GND-D2: 0VCan you please verify the above?
You did test a few USB modes, but there is one, very low-level from the SoC itself, you have not tried:
- turn it off and disconnect USB
- press both vol buttons and...
- plug in to a PC
Now your PC should register a new USB\VID_05C6&PID_9008 device [in QHSUSB_DLOAD mode]
Yes, the IC is an ESD suppressor. It may even absorb the hit from a faulty charger and protect the tablet from destruction by excessive power supply...
:highfive:
k23m said:
I checked N7's USB port....
Unit off, charger disconnected, ohmmeter measures:
GND-5V: 8kohm
GND-D1: 3Mohm
GND-D2: 3Mohm
D1-D2: 8Mohm
(meter polarity makes no difference)
Unit on, Android running, voltmeter measures:
GND-5V: 0V
GND-D1: 0V
GND-D2: 0VCan you please verify the above?
You did test a few USB modes, but there is one, very low-level from the SoC itself, you have not tried:
- turn it off and disconnect USB
- press both vol buttons and...
- plug in to a PC
Now your PC should register a new USB\VID_05C6&PID_9008 device [in QHSUSB_DLOAD mode]
Yes, the IC is an ESD suppressor. It may even absorb the hit from a faulty charger and protect the tablet from destruction by excessive power supply...
:highfive:
Click to expand...
Click to collapse
You're absolutely right, had no idea about QHSUSB_DLOAD mode. It works, there's hope, the hardware might be okay after all! Odd though, imagined the bootloader USB code was quite low level and standalone too, but maybe it shares libs with the rest of the system or something?
The connection details from USBTreeview, if it's of any use. Looks just fine to me at least, P/C 28 is of course just the missing driver:
Code:
=========================== USB Port1 ===========================
Connection Status : 0x01 (Device is connected)
Port Chain : 1-1-1
Properties : 0x01
IsUserConnectable : yes
PortIsDebugCapable : no
PortHasMultiCompanions : no
PortConnectorIsTypeC : no
======================== USB Device ========================
DriverKeyName : ERROR_FILE_NOT_FOUND
+++++++++++++++++ Device Information ++++++++++++++++++
Device Description : QHSUSB_DLOAD
Device ID : USB\VID_05C6&PID_9008\6&3A6A7FD9&0&1
Hardware IDs : USB\VID_05C6&PID_9008&REV_0000 USB\VID_05C6&PID_9008
Driver KeyName : -
Legacy BusType : PNPBus
Enumerator : USB
Location Info : Port_#0001.Hub_#0004
Location IDs : PCIROOT(0)#PCI(1A00)#USBROOT(0)#USB(1)#USB(1), ACPI(_SB_)#ACPI(PCI0)#ACPI(USBE)#ACPI(RHUB)#ACPI(PRT1)#USB(1)
Container ID : {acbd03bb-d39a-11e9-844a-f46d044eca1c}
Manufacturer Info : -
Capabilities : 0x04 (Removable)
Status : 0x01806400 (DN_HAS_PROBLEM, DN_DISABLEABLE, DN_REMOVABLE, DN_NT_ENUMERATOR, DN_NT_DRIVER)
Problem Code : 28 (CM_PROB_FAILED_INSTALL)
Power State : D3 (supported: D0, D2, D3, wake from D0, wake from D2)
+++++++++++++++++ Registry USB Flags +++++++++++++++++
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\usbflags\05C690080000
osvc : REG_BINARY 00 00
SkipContainerIdQuery : REG_BINARY 01 00 00 00
---------------- Connection Information ---------------
Connection Index : 0x01 (1)
Connection Status : 0x01 (DeviceConnected)
Current Config Value : 0x00
Device Address : 0x02 (2)
Is Hub : 0x00 (no)
Device Bus Speed : 0x02 (High-Speed)
Number Of Open Pipes : 0x00 (0 pipes to data endpoints)
Data (HexDump) : 01 00 00 00 12 01 00 02 00 00 00 40 C6 05 08 90 [email protected]
00 00 01 02 00 01 00 02 00 02 00 00 00 00 00 01 ................
00 00 00 ...
--------------- Connection Information V2 -------------
Connection Index : 0x01 (1)
Length : 0x10 (16 bytes)
SupportedUsbProtocols : 0x03
Usb110 : 1 (yes)
Usb200 : 1 (yes)
Usb300 : 0 (no)
ReservedMBZ : 0x00
Flags : 0x00
DevIsOpAtSsOrHigher : 0 (Is not operating at SuperSpeed or higher)
DevIsSsCapOrHigher : 0 (Is not SuperSpeed capable or higher)
DevIsOpAtSsPlusOrHigher : 0 (Is not operating at SuperSpeedPlus or higher)
DevIsSsPlusCapOrHigher : 0 (Is not SuperSpeedPlus capable or higher)
ReservedMBZ : 0x00
Data (HexDump) : 01 00 00 00 10 00 00 00 03 00 00 00 00 00 00 00 ................
---------------------- Device Descriptor ----------------------
bLength : 0x12 (18 bytes)
bDescriptorType : 0x01 (Device Descriptor)
bcdUSB : 0x200 (USB Version 2.00)
bDeviceClass : 0x00 (defined by the interface descriptors)
bDeviceSubClass : 0x00
bDeviceProtocol : 0x00
bMaxPacketSize0 : 0x40 (64 bytes)
idVendor : 0x05C6 (Qualcomm, Inc)
idProduct : 0x9008
bcdDevice : 0x0000
iManufacturer : 0x01 (String Descriptor 1)
iProduct : 0x02 (String Descriptor 2)
iSerialNumber : 0x00 (No String Descriptor)
bNumConfigurations : 0x01 (1 Configuration)
Data (HexDump) : 12 01 00 02 00 00 00 40 C6 05 08 90 00 00 01 02 [email protected]
00 01 ..
------------------ Configuration Descriptor -------------------
bLength : 0x09 (9 bytes)
bDescriptorType : 0x02 (Configuration Descriptor)
wTotalLength : 0x0020 (32 bytes)
bNumInterfaces : 0x01 (1 Interface)
bConfigurationValue : 0x01 (Configuration 1)
iConfiguration : 0x00 (No String Descriptor)
bmAttributes : 0x80
D7: Reserved, set 1 : 0x01
D6: Self Powered : 0x00 (no)
D5: Remote Wakeup : 0x00 (no)
D4..0: Reserved, set 0 : 0x00
MaxPower : 0x01 (2 mA)
Data (HexDump) : 09 02 20 00 01 01 00 80 01 09 04 00 00 02 FF FF .. .............
FF 00 07 05 81 02 00 02 00 07 05 01 02 00 02 00 ................
---------------- Interface Descriptor -----------------
bLength : 0x09 (9 bytes)
bDescriptorType : 0x04 (Interface Descriptor)
bInterfaceNumber : 0x00
bAlternateSetting : 0x00
bNumEndpoints : 0x02 (2 Endpoints)
bInterfaceClass : 0xFF (Vendor Specific)
bInterfaceSubClass : 0xFF
bInterfaceProtocol : 0xFF
iInterface : 0x00 (No String Descriptor)
Data (HexDump) : 09 04 00 00 02 FF FF FF 00 .........
----------------- Endpoint Descriptor -----------------
bLength : 0x07 (7 bytes)
bDescriptorType : 0x05 (Endpoint Descriptor)
bEndpointAddress : 0x81 (Direction=IN EndpointID=1)
bmAttributes : 0x02 (TransferType=Bulk)
wMaxPacketSize : 0x0200 (max 512 bytes)
bInterval : 0x00 (never NAKs)
Data (HexDump) : 07 05 81 02 00 02 00 .......
----------------- Endpoint Descriptor -----------------
bLength : 0x07 (7 bytes)
bDescriptorType : 0x05 (Endpoint Descriptor)
bEndpointAddress : 0x01 (Direction=OUT EndpointID=1)
bmAttributes : 0x02 (TransferType=Bulk)
wMaxPacketSize : 0x0200 (max 512 bytes)
bInterval : 0x00 (never NAKs)
Data (HexDump) : 07 05 01 02 00 02 00 .......
----------------- Device Qualifier Descriptor -----------------
Error : ERROR_GEN_FAILURE
-------------------- String Descriptors -------------------
String descriptors are not available (because the device has problem code CM_PROB_FAILED_INSTALL)
Didn't think any measurements were needed now when I got the QHSUSB_DLOAD mode working, but did them anyways since you asked me to. Now I'm really confused. Strangely enough, some of my measurements are very different from yours, and meter polarity seems to matter here. Perhaps my meter uses a higher voltage than yours, higher than the ESD suppressor forward voltage, or something? Still hard to explain the differences with Android running though...
Plugged in and measured through the USB Micro cable I cut and stripped before:
Unit off, charger disconnected, battery still connected:
GND-5V: 7.8kOhm (polarity independent)
GND-D-: 18.5 kOhm (-probe on GND) 4.1 kOhm (+probe on GND)
GND-D+: >40 MOhm (-probe on GND) 9.3 MOhm (+probe on GND)
D+-D-: 9.3 MOhm (+probe on D-), >40MOhm (-probe on D-)
Unit on, Android running:
GND-5V: 5.2VDC
GND-D1: 0V
GND-D2: 0.31VDC
Redid the measurements twice with the same results.
As you probably have noticed, I'm very much a novice in this field. Got no idea what the voltages and resistances are supposed to be. Is it possible it could be something with the charging circuitry? Another thought, there's [only?] 209 kOhm between the mode select pin and ground. Is it perhaps possible that my device is stuck in OTG mode?
Ah, it's some kind of zener barrier. Thought it might be for signal processing only first, but hard to determine by measurements when you're not sure it's not broken
Once again, thanks a lot for your time and effort in helping me out with this. I really appreciate it. Even if we don't find a solution, it's at least very interesting and educative
.kaputnik. said:
.....Perhaps my meter uses a higher voltage than yours
....Still hard to explain the differences with Android running though...
Plugged in and measured through the USB Micro cable I cut and stripped before:
Unit off, charger disconnected, battery still connected:
GND-5V: 7.8kOhm (polarity independent)
GND-D-: 18.5 kOhm (-probe on GND) 4.1 kOhm (+probe on GND)
GND-D+: >40 MOhm (-probe on GND) 9.3 MOhm (+probe on GND)
D+-D-: 9.3 MOhm (+probe on D-), >40MOhm (-probe on D-)
Unit on, Android running:
GND-5V: 5.2VDC
GND-D1: 0V
GND-D2: 0.31VDC
.....there's [only?] 209 kOhm between the mode select pin and ground. Is it perhaps possible that my device is stuck in OTG mode?
....Even if we don't find a solution, it's at least very interesting and educative
Click to expand...
Click to collapse
Your ohmmeter is different but we should see comparable results from the more consistent diode-test:
Unit off, charger disconnected, diode-test measures:
GND-5V: 2.6V; 0.5V reverse
GND-D1: 1.2V; 0.7V reverse
GND-D2: 1.2V; 0.7V reverse
D1-D2: 1.5V; 1.5V reverse
GND-ID: 0.8V; 0.8V reverseAs for the differences in Android, it seems that your micro cable is from an OTG adaptor and has pins 4 and 5 shorted, hence you get this 5V out and also active data. Please disconnect it and check the ID pin on diode-test.
Let's see the hardware logs. Please 'install' the attached file in TWRP within 3 minutes from initial reboot. Then find 'logs.tgz' in the root of internal storage and attach it here or upload somewhere and post a link.
This case is very interesting indeed, cheers! :good:
k23m said:
Your ohmmeter is different but we should see comparable results from the more consistent diode-test:
Unit off, charger disconnected, diode-test measures:
GND-5V: 2.6V; 0.5V reverse
GND-D1: 1.2V; 0.7V reverse
GND-D2: 1.2V; 0.7V reverse
D1-D2: 1.5V; 1.5V reverse
GND-ID: 0.8V; 0.8V reverseAs for the differences in Android, it seems that your micro cable is from an OTG adaptor and has pins 4 and 5 shorted, hence you get this 5V out and also active data. Please disconnect it and check the ID pin on diode-test.
Let's see the hardware logs. Please 'install' the attached file in TWRP within 3 minutes from initial reboot. Then find 'logs.tgz' in the root of internal storage and attach it here or upload somewhere and post a link.
This case is very interesting indeed, cheers! :good:
Click to expand...
Click to collapse
Ah, good idea
Unit off, charger disconnected, diode-test measures:
GND-5V: 2.3V; 0.5V reverse
GND-D1: 0.9V: 0.6V reverse
GND-D2: 0.9V; 0.6V reverse
D1-D2: 1.3V; 1.3V reverse
GND-ID: 0.8V; 0.7V reverse.
Did all measurements both with and without the cable, just to see if the cable introduced any effects. The results were identical.
A little lower across the block, but generally much more consistent with your readouts
As for the differences in Android, it seems that your micro cable is from an OTG adaptor and has pins 4 and 5 shorted
Click to expand...
Click to collapse
Well, if it was from an OTG cable, the GND-ID resistance would have been somewhere close to 0 ohm rather than the 209 kOhm I got yesterday Re-measured GND-ID just in case, without the cable, directly on the connector pins. Still 209 kOhm.
If you'd like, I could double check by measuring the 5VDC-GND voltage with the device powered again, directly on the connector pins, without the cable. Would rather not though, it's far too easy to slip with the probes and short something out.
Ran the system log collector twice. Booted to TWRP and ran the collector as quickly as I could, booted the system and downloaded/deleted the logs from the device, rebooted to TWRP again, and let it sit for 2 mins before running it a second time, to really give everything time to initialize properly.
Had to zip the logs, the forum wouldn't let me attach .tgz files. Hope you can find anything out. Had a look in the logs myself, and quickly established that this is way over my head, you really need to know what to look for for those to be of any use
.kaputnik. said:
...Well, if it was from an OTG cable, the GND-ID resistance would have been somewhere close to 0 ohm rather than the 209 kOhm I got yesterday Re-measured GND-ID just in case, without the cable, directly on the connector pins. Still 209 kOhm. ....
Click to expand...
Click to collapse
So, if not the cable, then we have an internal issue - your N7 is stuck in OTG mode. This mode is ignored by the low-level QHSUSB_DLOAD and only then PC can detect it or CHARGE IT when off! (except for modified Android kernels which enable charging in OTG mode)
No doubt about it, compare the logs....
Code:
your dmesg
<7>[ 2.876586] id_pin_irq_work_function: gpio_get_value(APQ_OTG_ID_PIN) = 0
<6>[ 2.876586] id_pin_irq_work_function: APQ_OTG_ID_PIN is low : Host mode
dmesg in normal mode
<7>[ 2.077331] id_pin_irq_work_function: gpio_get_value(APQ_OTG_ID_PIN) = 1
Final check - unit on, Android running, USB disconnected (non-OTG mode):
USB pins 5-4, voltmeter measures... GND-ID: 1.8VIf you measure below 1.8V, it is confirmed, and we will search for a remedy next... :fingers-crossed:
k23m said:
So, if not the cable, then we have an internal issue - your N7 is stuck in OTG mode. This mode is ignored by the low-level QHSUSB_DLOAD and only then PC can detect it or CHARGE IT when off! (except for modified Android kernels which enable charging in OTG mode)
No doubt about it, compare the logs....
Code:
your dmesg
<7>[ 2.876586] id_pin_irq_work_function: gpio_get_value(APQ_OTG_ID_PIN) = 0
<6>[ 2.876586] id_pin_irq_work_function: APQ_OTG_ID_PIN is low : Host mode
dmesg in normal mode
<7>[ 2.077331] id_pin_irq_work_function: gpio_get_value(APQ_OTG_ID_PIN) = 1
Final check - unit on, Android running, USB disconnected (non-OTG mode):
USB pins 5-4, voltmeter measures... GND-ID: 1.8VIf you measure below 1.8V, it is confirmed, and we will search for a remedy next... :fingers-crossed:
Click to expand...
Click to collapse
Confirmed, the GND-ID voltage with Android running and USB disconnected is only 347 mV.
Powered the device off again, and did some resistance measurements while at it. As mentioned before, the GND-ID resistance is 209 kOhm (or 0.8V with diode test). Disconnected the silvery FFC in the USB daughterboard end, GND-ID resistance jumped to > 40 MOhm. Reconnected the FFC and disconnected it in the motherboard end instead, still > 40 MOhm. That should rule out any issues with the FFC and USB daughterboard at least. Diode test with the FFC disconnected gives, 3.07V, max probing voltage of my multimeter (getting the same reading with probes in the air).
Did a quick checkup of the motherboard with a strong flashlight and a loupe. Nothing obvious visible to the eye, like burned components/PCB, signs of water ingress, [conductive] debris, etc. Leaving the motherboard removed by the way, in case there's something specific you want me to check.
If you feel like opening your N7 again, as a reference, what is your GND-ID resistance reading (powered off, USB disconnected) ?
From your second post in the thread, it looks like you have access to schematics etc. Googled around some, but could only find this kind of documentation for the 2012 model. You don't happen to have a link? Would probably be incredibly helpful with pin designation tables for the FFC connectors, etc, if available
This is getting really interesting now by the way
Edit: Judging by the log, it looks like the the OTG mode is controlled by a GPIO "pin" being pulled high or low. Guessing the circuitry leading up to the GPIO interface is quite simple. If the problem is something with the circuitry, rather than with the GPIO interface itself, I'm no stranger to desoldering components, cutting traces, etc and completely disable OTG mode. I'm never gonna use it. The N7 is just a "secondary device" nowadays, mostly used for watching movies, HMI for the ODB interface in the car, and cyberloafing on the toilet
Edit 2: Took a second closer look at the motherboard, and this time I found something when focusing on the components! What looks like an inductor to me, at the power supply management chip, is busted. Even found the chipped off fragment in the case. See attached photos.
Could definitely explain why that GPIO pin isn't high enough. Doubting I've caused that when removing the mobo, been very careful with it.
.kaputnik. said:
Disconnected the silvery FFC in the USB daughterboard end, GND-ID resistance jumped to > 40 MOhm
what is your GND-ID resistance reading (powered off, USB disconnected) ?
it looks like you have access to schematics
looks like an inductor to me, at the power supply management chip, is busted. Even found the chipped off fragment in the case.
Click to expand...
Click to collapse
OK, the daughterboard is not faulty. I measure 300kohm GND-ID resistance. No worries about the ferrite bit from the inductor.
I don't have the schematics and they would not help much in this multi-layer, compact PCB, BGA design. It seems that there is a conductive leak from the pin to GND caused by corrosion, or internal IC voltage pull-up resistor failure. So, let's try a simple mod to correct this situation. Please solder a 100kohm resistor between +5V and the ID - the area around USB port is most convenient for it. If the resistor is not enough to increase ID to 1.8V, then try 10k next. If still not enough, use 1k, but not any lower values.
Should this mod be unsuccessful, you can always use Timur's kernel which enables charging in OTG mode. :victory:
:highfive:
k23m said:
OK, the daughterboard is not faulty. I measure 300kohm GND-ID resistance. No worries about the ferrite bit from the inductor.
I don't have the schematics and they would not help much in this multi-layer, compact PCB, BGA design. It seems that there is a conductive leak from the pin to GND caused by corrosion, or internal IC voltage pull-up resistor failure. So, let's try a simple mod to correct this situation. Please solder a 100kohm resistor between +5V and the ID - the area around USB port is most convenient for it. If the resistor is not enough to increase ID to 1.8V, then try 10k next. If still not enough, use 1k, but not any lower values.
Should this mod be unsuccessful, you can always use Timur's kernel which enables charging in OTG mode. :victory:
:highfive:
Click to expand...
Click to collapse
Got no means of measuring inductance, but a resistance comparison to the other inductors in the same area, which looks identical, suggests the coil is ok at least. Assuming those are only for filtering out high frequency ripple, shouldn't matter if the inductance is a little bit off. So, no worries
Will try the mod once I'm a little less shaky, was out for a few beers yesterday night Had the same general idea yesterday, but waited in case you had a more elegant solution
Really hoping it'll work, would be nice to have fastboot access etc.
Edit: you don't happen to have a suggestion of a point to tap 5VDC from, that's powered when the device is not in OTG mode, btw? Hard for me to find one with a device stuck in OTG
.kaputnik. said:
....you don't happen to have a suggestion of a point to tap 5VDC from, that's powered when the device is not in OTG mode, btw? Hard for me to find one with a device stuck in OTG
Click to expand...
Click to collapse
Sure, I propose either the 4V or precise 3.0V. This ~4V comes almost directly from unregulated battery (via a MOSFET only) and needs to be handled carefully. If you prefer a safer option, but hard to reach tap, go for the 3.0V. Also, the shielded area of ELAN IC, the touch control chip, could be explored for more regulated voltage options. Personally I'd use 4V as it is right next to the ID test point near USB port.
:fingers-crossed:
k23m said:
Sure, I propose either the 4V or precise 3.0V. This ~4V comes almost directly from unregulated battery (via a MOSFET only) and needs to be handled carefully. If you prefer a safer option, but hard to reach tap, go for the 3.0V. Also, the shielded area of ELAN IC, the touch control chip, could be explored for more regulated voltage options. Personally I'd use 4V as it is right next to the ID test point near USB port.
:fingers-crossed:
Click to expand...
Click to collapse
So, tested with a 100 kOhm between the 4V point and ID yesterday morning, but it wasn't enough. The ID-GND voltage landed lower than I expected. Had some social stuff going on for the rest of the day, and also today, so had to put it aside until now.
Decided to do it experimentally instead, so soldered a couple of salvaged DIP socket pins to wire pieces, connected them to the 4V and ID test points, and started working through my resistor assortment downwards. At 8k2 charging started to work. The ID-GND voltage was still far from 1.8V though, more like 1.2V or something like that, but hell, it worked, was happy enough with that
Soldered in a 6k7 resistor to have some margin, and put the device back together again. Now it's happily charging. Will try fastboot mode etc later on, but I believe we can assume the mission is accomplished
I'm extremely impressed by your incredible patience and pedagogic, thorough way of putting things, leaving nothing out! If you ever get any technical problems with your > 30000 ton merchant ship, I'll gladly help you in return; that's my field of expertise, and probably the only place where I possibly could measure up to your help with this
Once again, thanks a lot!
Edit: a couple of pics from the modding, if you're interested:
.kaputnik. said:
So, tested with a 100 kOhm between the 4V point and ID yesterday morning, but it wasn't enough. The ID-GND voltage landed lower than I expected. Had some social stuff going on for the rest of the day, and also today, so had to put it aside until now.
Decided to do it experimentally instead, so soldered a couple of salvaged DIP socket pins to wire pieces, connected them to the 4V and ID test points, and started working through my resistor assortment downwards. At 8k2 charging started to work. The ID-GND voltage was still far from 1.8V though, more like 1.2V or something like that, but hell, it worked, was happy enough with that
Soldered in a 6k7 resistor to have some margin, and put the device back together again. Now it's happily charging. Will try fastboot mode etc later on, but I believe we can assume the mission is accomplished
I'm extremely impressed by your incredible patience and pedagogic, thorough way of putting things, leaving nothing out! If you ever get any technical problems with your > 30000 ton merchant ship, I'll gladly help you in return; that's my field of expertise, and probably the only place where I possibly could measure up to your help with this
Once again, thanks a lot!
Edit: a couple of pics from the modding, if you're interested:
Click to expand...
Click to collapse
Great news! Every fixed Nexus 7'13 makes me very happy :victory:
I wish we had its service manual with complete schematic diagrams and could diagnose more problems with better efficiency. It is a 6 year old tech and I hope that the schematics will eventually leak out on the internet.
Note to future readers - the 4V track goes right down to USB port area and if you scratch the paint, you could solder a small SMD resistor there without any wires. Thanks to kaputnik's experiments we now know it should be around 6.7k-4.7k.
Cheers :highfive: