OptiBee Energy Pro · USB expansion
One port. Four jobs, one at a time.
The USB port turns the controller into whatever the installation is missing: a wireless uplink, a second isolated network, another field bus, or a firmware stick. The drivers ship with the firmware — plug the adapter in and udev loads it. Nothing to enable in the web interface first.
The root hub reports one child, so exactly one adapter is attached at a time. WiFi, a second LAN and a firmware stick are mutually exclusive unless you add an external hub — and hubs are not supported.
WiFi uplink
For meter cabinets with no cable to the router. The station reconnects on boot, and if the wired link goes down the default route moves to WiFi on its own — measured over a full cable-pull cycle.
| Chipset | Driver | Adapter seen in the field | Notes |
|---|---|---|---|
| RTL8811CU / RTL8821CURecommended | rtw88 (RTW88_8821CU) | UGREEN CM448 / AC650 (20204) | Dual band, 802.11ac 1×1. AP-capable, but AP and station cannot run at the same time. Enumerates as a driver CD-ROM first and is switched over automatically.Verified on hardware |
| MT7610U | mt76 (MT76x0U) | ALFA AWUS036ACHM · Panda PAU0B | Dual band, 802.11ac 1×1. The only one of the three that can run AP and station concurrently, and it draws the least current — 160 mA measured.Driver ships in the firmware |
| RTL8188EU / 8188FU / 8192 / 8723 | rtl8xxxu | TP-Link TL-WN725N | 2.4 GHz 802.11n only. Retail SKUs under one product name silently change between 8188EU and 8188FU; both are covered, which is why three driver families ship instead of one.Verified on hardware |
Second Ethernet port
A side segment with its own DHCP address and deliberately no default route, so a grid-side or metering network stays separated from the house network. Both addresses are reachable at the same time.
| Chipset | Driver | Adapter seen in the field | Notes |
|---|---|---|---|
| AX88179 · AX88772Recommended | ax88179_178a · ax8817x | ASIX AX88179 (0b95:1790) | Gigabit. The adapter we use in-house and the one the failover behaviour was measured with.Verified on hardware |
| RTL8152 / 8153 / 8150 | r8152 · r8150 | Gigabit. The other dominant chipset in USB dongles.Driver ships in the firmware | |
| LAN95xx / 75xx / 78xx | smsc95xx · smsc75xx · lan78xx | Very common in unbranded dongles.Driver ships in the firmware | |
| AQC111 | aqc111 | Multi-gig dongles. The port negotiates at USB 2.0, so the link is not the limit here.Driver ships in the firmware | |
| CDC ECM / EEM / NCM · RNDIS | cdc_ether · cdc_eem · cdc_ncm · rndis_host | Standards-based and generic adapters, plus Windows-style tethering.Driver ships in the firmware | |
| DM9601 · MCS7830 | dm9601 · mcs7830 | Cheap no-name adapters, 100 Mbit.Driver ships in the firmware |
RS485 · CAN
A third field bus beyond the two built-in RS485 ports, or a CAN link to a battery that speaks it. Serial adapters get a stable /dev/usbserial0 symlink; a CAN adapter is renamed and brought up automatically at the configured bitrate.
| Chipset | Driver | Adapter seen in the field | Notes |
|---|---|---|---|
| CANRecommended | gs_usb | CANable / candleLight | Open hardware, available off the shelf. The bitrate comes from the device configuration and the link is brought up on plug.Driver ships in the firmware |
| CAN | peak_usb · 8dev_usb · esd_usb · mcba_usb · ucan | Commercial CAN dongles an installer may already own.Driver ships in the firmware | |
| RS485 / RS232 bridges | cp210x · ch341 · pl2303 · ftdi_sio | What cheap RS485 converters actually ship with. FTDI is covered too.Driver ships in the firmware | |
| /dev/ttyACM* | cdc-acm | Industrial converters and some CAN dongles expose a control port this way instead.Driver ships in the firmware |
KNX interface
A KNX TP bus with no IP router in between: the stick goes into the port and the bus is reachable. The KNX page finds it in the same scan that lists IP gateways and hands you the endpoint ready to paste. Group addresses come from the site’s own ETS export — KNX ships no brand template, because 4/0/1 is grid power in one building and a corridor light in the next.
| Chipset | Driver | Adapter seen in the field | Notes |
|---|---|---|---|
| KNX Std 9/3 (HID reports)Recommended | cEMI over usbfs | Weinzierl KNX-USB (0e77) and its rebrands | The interface IC inside most KNX USB sticks, so a bare usb:// endpoint already matches it. Registering the vendor:product that discovery reports skips the vendor list entirely.Spoken by the KNX app, no kernel driver |
| KNX Std 9/3 (HID reports) | cEMI over usbfs | any interface addressed as usb://vid:pid | Any other KNX USB interface can be addressed by its own vendor:product. Only one process may hold the stick at a time; a conflict shows up as a connection error and is retried with backoff.Spoken by the KNX app, no kernel driver |
Firmware stick
Offline firmware update. The partition is mounted read-only, the bundle is verified before anything is written, and the update is staged rather than applied straight from the stick.
| Chipset | Driver | Adapter seen in the field | Notes |
|---|---|---|---|
| USB mass storage | usb-storage | The bundle is checked before staging. Log export to a stick is not implemented.Driver ships in the firmware |
What the radio actually delivers
Measured on the device over SSH, 100 MB, same room and same access point. Both figures are well under the PHY rate — the USB path is the limit, not the antenna. Enough for firmware upload and the web interface; a wired link is still the better choice when one is available.
| Adapter | PHY rate | Band | Upload | Download |
|---|---|---|---|---|
| RTL8188EU | 72.2 Mbit/s | 2.4 GHz | 1.20 MB/s | 2.08 MB/s |
| RTL8811CU | 433.3 Mbit/s | 5 GHz · 80 MHz VHT | 6.26 MB/s | 10.95 MB/s |
What does not work
Listed because finding out on site costs more than reading it here.
- WiFi 6 USB dongles
RTL8832AU · RTL8851BU · RTL8852AU · mt7921u · mt7925u
- USB hubs
maxchild = 1
- Cellular modems
USB-WWAN / LTE
- Log export to a USB stick
- Hot-plugging the KNX interface — a replug needs a restart
Not sure which adapter fits your cabinet?
Send us the site conditions — cable or no cable, which bus is already occupied — and we will name a concrete part number.
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