In the world of DIY electronics, creating solutions that bridge the gap between different types of communication technologies is always a rewarding challenge. One such solution that is particularly useful in today's world of connectivity is building a USB to Ethernet adapter. This project allows devices that only have USB ports to communicate over an Ethernet network, which is useful for adding network connectivity to older devices, embedded systems, or even custom projects like a home automation system.

In this article, we’ll guide you step-by-step through the process of building your own USB to Ethernet adapter using the DM9601N chip, a popular and cost-effective USB-to-Ethernet controller. The DM9601N offers a simple interface for connecting a USB host to an Ethernet network, making it ideal for DIY projects.

What is the DM9601N?

The DM9601N is a USB 2.0 to Ethernet controller chip. It converts USB signals into Ethernet frames, enabling a device with a USB interface to communicate over an Ethernet network. It supports both 10/100 Mbps Ethernet and uses the standard USB 2.0 high-speed interface (480 Mbps) for data transfer.

Key Features:

· USB 2.0 High-Speed interface for fast data transmission (480 Mbps).

· 10/100 Mbps Ethernet support for reliable wired networking.

· Built-in PHY (Physical Layer) and MAC (Media Access Controller) for Ethernet communication.

· Plug and Play compatibility with most operating systems like Linux, Windows, and macOS.

· Low power consumption—ideal for embedded systems and portable devices.

· Supports TCP/IP and UDP protocols, making it versatile for various networking applications.

· Integrated USB 2.0 transceiver to simplify design and reduce external components.

The DM9601N is an excellent choice for creating a USB-to-Ethernet bridge because it is both inexpensive and highly functional, offering an easy-to-use solution for network connectivity.

Components and Tools Needed

To build the USB to Ethernet adapter, you will need the following components:

Components:

· DM9601N USB to Ethernet Controller Chip

· RJ45 Ethernet Connector: For connecting the adapter to the network.

· USB Type-A or Micro-B Connector: To connect to the USB host.

· Capacitors: 0.1µF for filtering and stabilization.

· Resistors: 1kΩ for pull-up or pull-down as required by the chip.

· Inductor: For filtering the power supply.

· LEDs: For power and Ethernet status indication (optional).

· Diodes: To protect against electrostatic discharge (ESD) on the Ethernet and USB lines.

· PCB (Printed Circuit Board): To mount the components and connect everything.

· Power Supply: 5V from USB or an external supply if using a microcontroller.

· Ethernet Cable: To connect your device to the network.

· Microcontroller or Host Device (Optional): If you’re using a microcontroller like Arduino or Raspberry Pi, you’ll need that to interface with the USB.

Tools:

· Soldering Iron and Solder: For assembling components on the PCB.

· Multimeter: To check for continuity and voltage.

· Oscilloscope (Optional): For signal analysis, especially for USB or Ethernet signals.

· Wire Cutters and Strippers: To prepare wires for connections.

· USB Cable: To connect to the USB host device.

· PCB Design Software: For creating your schematic and PCB layout (e.g., KiCad or Eagle).

Step 1: Understanding the DM9601N

Before jumping into the design and assembly process, it’s important to understand how the DM9601N chip works. The DM9601N is designed to act as a bridge between a USB host (such as a computer or microcontroller) and an Ethernet network.

The key part of the chip is its ability to translate USB data packets into Ethernet frames, and vice versa, allowing seamless data exchange over the network. Here's a breakdown of the primary features:

USB Interface:

· The chip interfaces with the USB host through the D+ and D- lines (data lines). It follows the USB 2.0 protocol, which supports high-speed data transfer at 480 Mbps.

· VCC and GND power pins supply the DM9601N, typically using 5V from the USB host or a separate power source.

Ethernet Interface:

· The ETH_TX and ETH_RX pins connect to the Ethernet jack (RJ45), transmitting and receiving Ethernet data.

· ETH_CLK provides the clock signal to synchronize Ethernet communication.

· The PHY and MAC layers of the DM9601N are integrated, so external Ethernet components aren’t required.

Step 2: Designing the Schematic

Let’s break down the steps involved in designing the schematic for the USB to Ethernet adapter.

1. USB Interface

The D+ and D- data lines from the USB interface need to be connected to the corresponding pins on the DM9601N chip. The VCC pin should be connected to the 5V power supply (either from the USB or an external supply), and GND connects to the ground.

· D- (Pin 3) and D+ (Pin 4) should connect directly to the USB D- and USB D+ lines.

· VCC (Pin 1) should be connected to 5V.

· GND (Pin 2) should be connected to GND.

2. Ethernet Interface

Next, we need to route the ETH_TX and ETH_RX signals from the DM9601N to the RJ45 Ethernet jack. These two pins send and receive Ethernet frames over the network.

· ETH_TX (Pin 5) connects to the TX pin on the RJ45 connector.

· ETH_RX (Pin 6) connects to the RX pin on the RJ45 connector.

· ETH_CLK (Pin 7) connects to the Ethernet clock input if needed.

3. Power Supply and Decoupling

The DM9601N requires stable power for proper operation. You should include 0.1µF and 10µF capacitors to filter the power supply and reduce noise. These capacitors should be placed close to the VCC and GND pins.

4. LED Indicators (Optional)

You can use LEDs to indicate the operational status of the adapter. For instance:

· Power LED: Lights up when the device is powered.

· Ethernet Link LED: Indicates whether the Ethernet connection is active.

Use 330Ω to 1kΩ resistors in series with the LEDs to limit current and prevent damage.

5. ESD Protection

To protect the USB and Ethernet lines from electrostatic discharge, place ESD protection diodes on the D+, D-, ETH_TX, and ETH_RX lines.

Step 3: PCB Layout and Assembly

Now that you have the schematic, it's time to design the PCB layout.

1. PCB Design

Using tools like KiCad or Eagle, lay out your PCB, keeping the following in mind:

· Keep the USB D+ and D- lines as short as possible to prevent signal degradation.

· Route the ETH_TX and ETH_RX lines carefully, ensuring minimal interference with other signals.

· Place capacitors and other components close to the relevant pins for optimal performance.

After creating the PCB design, send the design files to a PCB manufacturer to have the board fabricated.

2. Soldering

Once the PCB arrives, it’s time to solder the components. Start with the DM9601N chip, followed by the resistors, capacitors, and connectors. Use a soldering iron and fine-tip soldering wire for precise soldering.

3. Testing the Circuit

Before connecting the USB to an actual device, verify the following:

· Power Supply: Ensure that the 5V supply is stable.

· Connections: Check all connections with a multimeter for continuity.

· USB Data Lines: Use an oscilloscope to ensure proper data transmission on the D+ and D- lines.

Step 4: Programming and Testing

The DM9601N chip is plug-and-play for most operating systems, meaning no special driver installation is needed for Linux, Windows, or macOS. However, if you're using an embedded system like a Raspberry Pi or Arduino, you may need to configure the software to recognize the USB Ethernet adapter.

1. Testing on a PC

Plug the USB-to-Ethernet adapter into a USB port on a computer or microcontroller. If your system supports plug-and-play, it should automatically detect the device and install the necessary drivers.

2. Testing the Ethernet Connection

Once detected, connect an Ethernet cable from the RJ45 port to a router or switch. The Ethernet Link LED should light up, indicating an active connection.

Check your network settings:

· Windows: Look for the new network interface in the Network Connections section.

· Linux: Run ifconfig or ip a to see the new Ethernet interface.

· macOS: Check the Network Preferences to find the new connection.

You can verify the connection by pinging another device on the network or accessing a website via a web browser.

Step 5: Debugging and Final Adjustments

If the device doesn't work as expected:

· Verify the USB connection is active by checking the data lines with an oscilloscope.

· Ensure the Ethernet link is established by checking the LED indicators.

· Use a multimeter to check the voltage levels at various pins of the DM9601N to ensure they are within the expected range.

Once everything is working, you have successfully built a USB to Ethernet adapter using the DM9601N chip.

Conclusion

Building a USB to Ethernet adapter with the DM9601N chip is a rewarding and practical DIY project that allows you to extend the functionality of USB-only devices by enabling them to communicate over an Ethernet network. With careful design, assembly, and testing, you can create a custom solution for adding network connectivity to embedded systems, older computers, or other devices.

The DM9601N chip is a powerful yet simple-to-use controller for this project, offering high-speed data transfer and seamless integration with most operating systems. By following the steps outlined in this article, you can easily add Ethernet capabilities to any USB-enabled device, opening up a world of possibilities for your DIY electronics projects.