Question Strange behaviour of usb ports

Mar 20, 2021
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Hi,
I have Asus X550Vx with W7 pro. It has 2 USB3 and 1 USB2 ports. One of the USB3 port is behaving unexpectedly. Below table shows what is happening. I'm electronic engineer, faced many strange responses but this is something different, couldn't get any idea.
Trials are done with two flash memories, two USB SSD's (type C), three cables/adapters and two mouses.
Flash 1 (32GB USB3) : Works at USB3/1, works at USB3/2, works at USB2
Flash 2 (16GB USB2) : Works at USB3/1, doesn't work at USB3/2, works at USB2
Both mouses : Works at USB3/1, doesn't work at USB3/2, works at USB2
SSD 1 with 1.5m cable : Works at USB3/1, doesn't work at USB3/2, works at USB2
SSD 1 with 50cm cable : Works at USB3/1, works at USB3/2, works at USB2
SSD 1 with adapter (4cm) : Works at USB3/1, doesn't work at USB3/2, works at USB
SSD 2 with 1.5m cable : Doesn't work at USB3/1, doesn't work at USB3/2, works at USB2
SSD 2 with 50cm cable : Works at USB3/1, works at USB3/2, works at USB2
SSD 2 with adapter (4cm) : Works at USB3/1, doesn't work at USB3/2, works at USB
Changing direction of type-C usb has no affect.
Voltages are measured, no difference between USB3/1 and USB3/2.
At visual inspection of contacts I didn't see any abnormalities.
It seems USB3/2 port has somthing wrong , also is selecting cable, interestingly the 50cm cable is giving more satisfactory result than 4cm adapter, which is unusual. I didn't expect any better result with 1.5 cable but just tried.
If anybody has any idea appreciated. I will open up the notebook to investigate the circuit from usb to cpu but don't expect too much, it is generally very simple and no parts to touch.
If I could I want to uninstall USB3 drivers and let USB3 ports to work as USB2.
Sabri
 
Mar 20, 2021
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Thank you,

I have a USB2 4 port hub with external power connection.
The hub cannot be detected on USB3/2 port but no problem at USB3/1.
I measured several voltage and currents with these ports when hub is connected.

Non-working port USB3/2 :
Ext power not supplied : 5.00V
Ext power supplied : 5.08V
Pin 2 voltage is 0.1V, pin 3 is 0.0V
Current drawn by hub : 100mA (when hub supply is connected drops to 0).
When flash memory is plugged in 160mA.
When SSD is added 500mA, flickering (current is not enough).
When ext power is applied current drops to 0, when taken out 500mA stable,
may mean SSD is stabilized, but still cannot be detected.
In none of above conditions the hub is not seen, no response as "could not be identified", nothing.

Working port, USB3/1 :
Ext power not supplied : 5.08V
Ext power supplied : 5.08V
Pin 2 voltage is 0.4V, pin 3 is 0.3V
Other current values are same as above.
Hub is seen and connected devices are detected.

This 0.08V difference between ext power is connected and not connected may mean three things,
-- either power supply of that port has something wrong,
-- or there is a contact resistance,
-- or there is ripple on VCC.
Voltages are observed by oscilloscope, no ripple on VCC, clear.
Also no spikes are observed that may appear because of bad contact.

I will continue deeper investigation on power supply of the port.

Sabri
 

vov4ik_il

Respectable
Good, so partially sorted.
One clarification, is the port hooked to the motherboard via header, or is it soldered to the board? It sounds like there is attenuation on the serial lines involved on the 3/2, which causes it to only work with low-power / low-speed devices.
 
Mar 20, 2021
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Yes, the main suspect is a resistance occured at supply line. But it doesn't explain why the usb3 ssd's are working with 50cm cable but fails with the adaptor. Also the usb3 flash is working but usb2 flash is not working, even mouse is not working. Probably there is something wrong with data lines also. I don't know if there is a hardware point that indicates connected device is USB2 or USB3, if so then it may not be working, all connected devices were treated as usb3, trying communicate in usb3 speed with usb2 device was failing. USB3 drivers are update. I even re-installed the system, no difference.
USB socket is directly soldered on mainboard, I don't expect cold or broken solder at connections.
 

vov4ik_il

Respectable
Yes, the main suspect is a resistance occured at supply line. But it doesn't explain why the usb3 ssd's are working with 50cm cable but fails with the adaptor.
Also the usb3 flash is working but usb2 flash is not working, even mouse is not working. Probably there is something wrong with data lines also. I don't know if there is a hardware point that indicates connected device is USB2 or USB3, if so then it may not be working, all connected devices were treated as usb3, trying communicate in usb3 speed with usb2 device was failing. USB3 drivers are update. I even re-installed the system, no difference.
USB socket is directly soldered on mainboard, I don't expect cold or broken solder at connections.
USB 3 is totally separate from USB 2 and only shares power delivery. If USB 2 data lines are not working (zapped by static for example, or disabled logically in BIOS for some reason) it should yield the results you have. The longer-cable-not-working issue is likely a voltage drop.
I would measure the resistance (power off, cold) on D+/D- and compare it against a working port, might give you a clue.
 

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