Expanding Dock (Color Printing Submission)

       A docking station, also known as a port replicator, is an external device designed specifically for laptops. By replicating or even expanding the ports of a laptop, it allows for convenient one-stop connection between the laptop and multiple accessories or external devices (such as power adapters, network cables, mice, external keyboards, printers, and external monitors).
       Next, I will explain the function and characteristics of the components based on the schematic diagram.
       First, let's look at the chip section.
The device with the reference number X1 is NX3225SA-12MHz-STD-CSR-6, which is a passive crystal oscillator. Here are some concepts we need to know:

Crystal is short for Crystal Resonator, also known as a passive crystal. It generally utilizes the piezoelectric effect of quartz crystals to generate a high-precision oscillation frequency. Passive crystals require capacitors and resistors to oscillate.


An active crystal oscillator is short for Crystal Oscillator. Active crystal oscillators integrate the oscillation circuit internally and can operate normally without the need for additional external components, but they require an external power supply.
A passive crystal oscillator (crystal) is mainly composed of a quartz crystal, a base, a casing, silver paste, and silver. Essentially, it's a quartz crystal resonator that utilizes the piezoelectric effect of quartz crystals to generate a high-precision oscillation frequency. A passive crystal oscillator has two pins, is non-polarized, and requires a clock circuit to generate an oscillation signal; it cannot oscillate on its own and is therefore a passive component.
Passive crystal oscillators require matching capacitors.
We use passive crystal oscillators to generate frequency for our circuits. We connect two 10uF capacitors to the passive crystal oscillator to form a circuit, enabling it to function.
The chip we use is the SL2.1A.
The SL2.1A is a highly integrated, high-performance, low-power USB 2.0 hub controller chip. This chip uses STT technology, a single power supply, and a 5V supply voltage. It internally integrates a 5V to 3.3V converter, requiring only an external power supply filter capacitor. The chip has a built-in reset circuit, and its low-power technology makes it even more outstanding.
The middle two pins of the male connector of the main interface are configured as the USB uplink DP signal and USB uplink DM signal of SL2.1A, respectively. A 10uF capacitor is also included in the main interface circuit for resonance and filtering.
The middle two pins of the two female connectors of the expansion interface are configured as the USB DP signal and USB DM signal of Downlink Port 1 and Downlink Port 2, respectively. A 100uF capacitor is connected to each of the two female connectors for filtering.
This is the relevant architecture of this project. Welcome friends and teachers to exchange ideas, provide guidance, and ask questions.
Below is a physical demonstration.