USB dongle can not identify, what is the reason, how to solve it?
From my maintenance experience, I can not recognize, one is that the computer can not recognize USB device.
Second, USB device can not be recognized by computer. We need to judge whether it is a computer problem or a USB device. We can use other USB devices to test the computer for problems.
If it's a computer problem. Is your computer damaged by a virus. Is the USB2.0 driver installed or version incompatible. Is there a software conflict (first solve the software problem) generally come up with a prompt to install the driver.
If it's a computer hardware problem. We first use a multimeter to measure four wires of USB (red + 5V white data data green data data black ground wire) multimeter red probe to ground black probe (white wire and other wire). The resistance value of the two lines is from the South Bridge. If the resistance value changes too much, it can be judged that it is the South Bridge problem. The USB module inside Nanqiao is burned down.
Come and see the USB devices outside now a lot of drivers are required. Even without a driver, it will not come out of the unrecognized situation. There are several situations that are not recognized. A USB data cable is not connected or is not in good contact with that place generally because it may be rusty and bloated in the place for a long time, and there may be something in it. The two USB cable is not available. Red line can not react to any reaction, white line is not recognizable. The green line is not clear or recognizable. White and green lines cannot be reversed. It's also unrecognized. The black line is not working and it doesn't respond. This measurement method has been mentioned above.
Note. Low voltage of red line 5V can also cause unrecognizable
Three USB board internal problems. 1. Poor crystal vibration, no vibration. 2. Two poor crystal vibration capacitance (20p)
3. Poor reset capacitance resistance. The reset voltage is too high at the bottom. 4. The three terminal IC is not good enough to provide the IC with voltage less than 5
Bad main IC