---
name: "atu"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/atu"
---

# atu(4)

Atmel AT76C50x USB IEEE 802.11b wireless network device

## NAME

**atu** – Atmel AT76C50x USB IEEE 802.11b wireless network device

## SYNOPSIS

**atu\* at uhub? port ?**

## DESCRIPTION

The **atu** driver provides support for wireless network adapters based around the Atmel AT76C503, AT76C503A, AT76C505, and AT76C505A USB chipsets and four companion radio chipsets.

The **atu** driver encapsulates all IP and ARP traffic as 802.11 frames, though it can receive either 802.11 or 802.3 frames.

These are the modes the **atu** driver can operate in:

- BSS mode

  Also known as *infrastructure* mode, this is used when associating with an access point, through which all traffic passes. This mode is the default.

- IBSS mode

  Also known as *IEEE* *ad-hoc* mode or *peer-to-peer* mode. This is the standardized method of operating without an access point. Stations associate with a service set. However, actual connections between stations are peer-to-peer.

The **atu** driver can be configured to use hardware Wired Equivalent Privacy (WEP). It is strongly recommended that WEP not be used as the sole mechanism to secure wireless communication, due to serious weaknesses in it.

The **atu** driver can be configured at runtime with [ifconfig(8)](/ifconfig/8.md) or on boot with [hostname.if(5)](/hostname.if/5.md).

## FILES

The adapter needs some firmware files, which are loaded on demand by the driver when the device is attached:

- */etc/firmware/atu-at76c503-i3863-int*

  - */etc/firmware/atu-at76c503-i3863-ext*

  - */etc/firmware/atu-at76c503-rfmd-acc-int*

  - */etc/firmware/atu-at76c503-rfmd-acc-ext*

  - */etc/firmware/atu-at76c505-rfmd-int*

  - */etc/firmware/atu-at76c505-rfmd-ext*

  - */etc/firmware/atu-intersil-int*

  - */etc/firmware/atu-intersil-ext*

  - */etc/firmware/atu-rfmd-int*

  - */etc/firmware/atu-rfmd-ext*

  - */etc/firmware/atu-rfmd2958-int*

  - */etc/firmware/atu-rfmd2958-ext*

  - */etc/firmware/atu-rfmd2958smc-int*

  - */etc/firmware/atu-rfmd2958smc-ext*

  ## HARDWARE

The following devices are known to be supported by the **atu** driver:

- 3Com 3CRSHEW696

  - AboCom BWU613

  - Accton 2664W

  - Acer Peripherals AWL300

  - Acer Peripherals AWL400

  - Actiontec 802UAT1

  - Addtron AWU120

  - Aincomm AWU2000B

  - Askey Computer Voyager 1010

  - Askey Computer WLL013 (Intersil Radio)

  - Askey Computer WLL013 (RFMD Radio)

  - Atmel AT76C503 (Intersil Radio)

  - Atmel AT76C503 (RFMD Radio)

  - Atmel AT76C505 (RFMD Radio)

  - Atmel AT76C505 (RFMD 2958 Radio)

  - Atmel AT76C505A (RFMD 2958 Radio)

  - Atmel AT76C505AS (RFMD 2958 Radio)

  - Belkin F5D6050

  - Bluetake BW002

  - Compaq iPAQ h54xx/h55xx Internal WLAN

  - Conceptronic C11U

  - Conceptronic WL210

  - Corega WLAN USB Stick 11

  - Dick Smith Electronics CHUSB 611G

  - Dick Smith Electronics WL200U

  - Dick Smith Electronics WL240U

  - Dick Smith Electronics XH1153

  - D-Link DWL-120 rev E

  - Geowave GW-US11S

  - Gigabyte GN-WLBM101

  - Gigaset WLAN

  - Hewlett-Packard HN210W

  - Intel AP310 AnyPoint II

  - I/O DATA USB WN-B11

  - Lexar 2662W-AR

  - Linksys WUSB11 802.11b

  - Linksys WUSB11 802.11b v2.8

  - MSI WLAN

  - Netgear MA101

  - Netgear MA101 rev B

  - OQO model 01 WiFi

  - Ovislink AirLive WL-1120USB

  - OvisLink AirLive WL-1130USB

  - Planex Communications GW-US11S

  - Samsung SWL2100W

  - Siemens WLL013

  - SMC EZ Connect 11Mbps (SMC2662w)

  - SMC EZ Connect 11Mbps v2 (SMC2662wV2)

  - Tekram U-300C

  - TRENDnet TEW-229UB

  - W-Buddie WN210

  - Z-Com M4Y-750

  ## EXAMPLES

The following example scans for available networks:

```
# ifconfig atu0 scan
```

The following [hostname.if(5)](/hostname.if/5.md) example configures atu0 to join network “mynwid”, using WEP key “mywepkey”, obtaining an IP address using DHCP:

```
join mynwid nwkey mywepkey
inet autoconf
```

## SEE ALSO

[arp(4)](/arp/4.md), [ifmedia(4)](/ifmedia/4.md), [intro(4)](/intro/4.md), [netintro(4)](/netintro/4.md), [usb(4)](/usb/4.md), [hostname.if(5)](/hostname.if/5.md), [ifconfig(8)](/ifconfig/8.md)

## AUTHORS

The **atu** driver was written by Daan Vreeken and ported to OpenBSD by Theo de Raadt and David Gwynne.

## CAVEATS

The **atu** driver does not support a lot of the functionality available in the hardware. More work is required to properly support the IBSS, power management, and selectable transmission rate features.