# USB to Ethernet passthrough mode

## General information

<p class="callout info">This feature is supported only by "**U**" series devices and SLZB-Ultima  
(CPU model: ESP32S3)</p>

USB to Ethernet passthrough mode allows connecting a USB device to your coordinator USB port (directly or via a USB hub) and using such USB devices remotely over IP.  
For example, a USB Z-Wave adapter can be connected and used remotely, similarly to an Ethernet-based Z-Wave coordinator.

## What devices can be connected?

1. Devices on **CP210x** chipset
2. Devices on **PL2303** chipset
3. Devices on **CH340** chipset
4. Devices on **CH341** chipset
5. Devices on **CH9102** chipset
6. Other **CDC-ACM** devices

<p class="callout info">**CDC-ACM** is typically used in microcontrollers such as the ESP32-S3/S31/P4, STM32, and others.  
Therefore, if your USB dongle is based on a microcontroller that supports USB, there is a high probability that it uses CDC-ACM.  
</p>

<p class="callout warning">We cannot guarantee support for all third-party CDC-ACM devices.</p>

## How many USB devices can be connected?

### SLZB-OS versions up to v3.4.2.dev1

**Only one USB device.**

### v3.4.2.dev1 and later

Update v3.4.2.dev1 allows the simultaneous use of two USB dongles, provided they are not based on the CH34x chip. Please check the table below for more details:

<table id="bkmrk-device1-%C2%A0-device2%C2%A0-c" style="width: 63.2143%;"><thead><tr><th style="width: 32.0623%;"><span style="text-decoration: underline;">Device1</span>

 Device2**

</th><th style="width: 16.4282%;"><span style="text-decoration: underline;">CP210x</span></th><th style="width: 15.4717%;"><span style="text-decoration: underline;">FTDI</span></th><th style="width: 18.3019%;"><span style="text-decoration: underline;">CDC-ACM</span></th><th style="width: 17.7358%;"><span style="text-decoration: underline;">CH34x</span></th></tr></thead><tbody><tr><td style="width: 32.0623%;">**CP210x**</td><td style="width: 16.4282%;">✅ </td><td style="width: 15.4717%;">✅ </td><td style="width: 18.3019%;">✅ </td><td style="width: 17.7358%;">❌ </td></tr><tr><td style="width: 32.0623%;">**FTDI**</td><td style="width: 16.4282%;">✅ </td><td style="width: 15.4717%;">✅</td><td style="width: 18.3019%;">✅ </td><td style="width: 17.7358%;">❌ </td></tr><tr><td style="width: 32.0623%;">**CDC-ACM**</td><td style="width: 16.4282%;">✅</td><td style="width: 15.4717%;">✅</td><td style="width: 18.3019%;">✅ </td><td style="width: 17.7358%;">❌ </td></tr><tr><td style="width: 32.0623%;">**CH34x**</td><td style="width: 16.4282%;">❌</td><td style="width: 15.4717%;">❌ </td><td style="width: 18.3019%;">❌ </td><td style="width: 17.7358%;">❌ </td></tr></tbody></table>

- Any pair without CH34x fits.
- No CH34x-based pair fits.

##### USB hub rules

1. If **two** devices are open, there cannot be a third one **connected** on the hub
2. If only **one** device is open: you can keep 3 **unopened** devices connected.
3. Additional USB hubs are not permitted.

## How much power can the coordinator provide via USB?

The coordinator can provide up to 1A.  
The optimal current is 500mA.

<p class="callout danger">If you are using a **powered** USB hub, please make sure that PoE is disabled!  
It is **forbidden** to use **PoE** and a **powered** USB hub at the **same** time!</p>

## USB to Ethernet passthrough setup

### 1. Mode select

Open the "USB" page and activate "Enable USB to Ethernet passthrough mode" and "Use new USB driver"

[![image.png](https://smlight.tech/support/manuals/uploads/images/gallery/2026-02/scaled-1680-/2Bwimage.png)](https://smlight.tech/support/manuals/uploads/images/gallery/2026-02/2Bwimage.png)

<p class="callout info">We recommend using the "Use new USB driver" option as the new driver provides greater stability and a wider list of supported USB devices.  
**The old driver will be removed in future updates!**</p>

<p class="callout info">**Starting with v3.4.2.dev1 new driver is used by default. There no more driver selector!**</p>

### 2. Connect your USB device and reboot your coordinator

### 3. Select your USB device  


Select your USB device from the list.

[![image.png](https://smlight.tech/support/manuals/uploads/images/gallery/2026-02/scaled-1680-/TbNimage.png)](https://smlight.tech/support/manuals/uploads/images/gallery/2026-02/TbNimage.png)

"Empty" - passthrough server disabled.  
"Any serial device" - the system will select the first device found and try to open interface 0.

<p class="callout info">**The interface has been redesigned starting from v3.4.2.dev1**</p>

[![image.png](https://smlight.tech/support/manuals/uploads/images/gallery/2026-09/scaled-1680-/rUIimage.png)](https://smlight.tech/support/manuals/uploads/images/gallery/2026-09/rUIimage.png)

Now you need to click the "Open" button on the card for the desired device to enable USB pass-through for it.

[![image.png](https://smlight.tech/support/manuals/uploads/images/gallery/2026-09/scaled-1680-/Ovyimage.png)](https://smlight.tech/support/manuals/uploads/images/gallery/2026-09/Ovyimage.png)

### 4. Set the serial speed  


The most common setting is 115200.

<p class="callout info">The serial speed depends on the firmware of your dongle. If you don't know what to choose, please contact the support service of the dongle manufacturer.</p>

### 5. Choose an interface  


[![image.png](https://smlight.tech/support/manuals/uploads/images/gallery/2026-02/scaled-1680-/ztgimage.png)](https://smlight.tech/support/manuals/uploads/images/gallery/2026-02/ztgimage.png)

Most USB devices will only have one interface - interface 0.  
But some devices may have several: for example one for `firmware update/debug` and another for `communication`.

<p class="callout info">If your device has multiple interfaces then you will have to try them all until you find correct one.</p>

<p class="callout success">For **ZWA-2** you need to select interface **1**</p>

<p class="callout info">**The interface has been redesigned starting from v3.4.2.dev1**</p>

[![image.png](https://smlight.tech/support/manuals/uploads/images/gallery/2026-09/scaled-1680-/YWSimage.png)](https://smlight.tech/support/manuals/uploads/images/gallery/2026-09/YWSimage.png)

Key changes in **v3.4.2.dev1**

- The interface selector now displays only those supported by the driver. You will no longer see interfaces that the driver cannot open.
- The new BSL button uses the DTR/RTS lines to activate your dongle's bootloader (if supported by the dongle).
- You can open and close devices, as well as change the baud rate and other settings, in real time. A restart is no longer required.
- The list of connected USB devices updates in real time.

### 6. About autoboot  


Some dongles have an autoboot circuit that puts the radio module into bootloader mode using the DTR/RTS lines, for example SLZB-07p7/p10.  
For such a dongle to work you need to select the option "My dongle has autoboot".

<p class="callout info">Most dongles that have autoboot use the **CH340** or **CP2102x** chipsets.  
If you don't know if your dongle has autoboot, please contact the support service of the dongle manufacturer.</p>

### 7. After setup

After you have selected all the settings, please click the "Save" button and restart the coordinator for the changes to take effect.

### 8. Host application settings

Most programs use the format `tcp://ip:port` or `socket://ip:port`, less often just `ip:port`

```
Examples:
tcp://192.168.50.196:8638
socket://192.168.50.196:8638
192.168.50.196:8638
```

If your host program has "RTS/CTS" or "Hardware flow control" settings, you should select "**disabled**"