Lenovo Zhaoyang e46a notebook

Today, we came back to a very strange problem: Our product cannot communicate through a direct connection network cable to the laptop. We must connect to the serial port at the same time to communicate. With such a big problem, the leaders asked me to solve it.

I have read the phenomenon. It is indeed such a phenomenon.

Environment where the problem occurs: The NIC chip of our product is rtl8019s, and the connection laptop is Lenovo Zhaoyang e46a.

Phenomenon: ping the laptop when the network cable is directly connectedProgramThe connection to this product does not communicate (the physical connection light is always on [the physical connection light is switched off to a successful connection]), and the connection string line is also connected, so the communication is normal. This problem does not occur in the case of a crossover network cable.

Comparison Test 1: using a common desktop computer (self-collected computer), the cross-line and direct-line communication is normal.

Comparison Test 2: using a DELL notebook (without a serial port), the cross line and direct line communication are normal.

Comparison Test 3: The use of IBM notebook and HP notebook (without serial port), the cross line and direct line communication is normal.

So I suspect that it is a problem with Lenovo Zhaoyang e46a with serial ports.

Further test: because our serial port only connects the RX, TX, And Gnd pins and casings. Therefore, I used tin wire to connect these places one by one, and found that pin 2, that is, the Tx pin, will communicate with each other. When no connection is made, the physical connection light will display an exception. Further Detection: connect the Tx pins of Zhaoyang notebook to the protection area of our product, and the communication is normal.

It is concluded that Lenovo Zhaoyang e46a notebook hardware design has problems.