atw4

Usage

Overview

The atw driver supports PCI/CardBus 802.11b wireless adapters based on the ADMtek ADM8211.

The ADM8211 is a bus-mastering 802.11 Media Access Controller (MAC) which is derived from ADMtek's DEC/Intel 21143 clones (see dc(4) for more information). It supports contention-free traffic (with an 802.11 Point Coordinator). The ADM8211 integrates an RF3000 baseband processor (BBP) by RF Microdevices.

In a typical application, the ADM8211 is coupled with an RF front-end by RFMD and a Silicon Laboratories Si4126 RF/IF synthesizer.

With the ADM8211, the division of labor between the host and NIC is different than with firmware-based NICs such as an(4) and wi(4). The ADM8211 is still responsible for real-time 802.11 functions such as sending ACK/RTS/CTS/ATIM frames, sending beacons, and answering CF polls from the access point, but the host takes responsibility for providing 802.11 functions such as scanning, association, and authentication. The host is also responsible for programming both the BBP and the RF/IF synthesizer.

These are the modes the atw 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 atw driver can be configured to use hardware Wired Equivalent Privacy (WEP) (though see BUGS, below). It is strongly recommended that WEP not be used as the sole mechanism to secure wireless communication, due to serious weaknesses in it.

The atw driver can be configured at runtime with ifconfig(8) or on boot with hostname.if(5).

Hardware

The atw driver supports PCI and CardBus cards using revisions 0x11 and 0x15 of the ADM8211 (aka ADM8211A) and revision 0x20 (aka ADM8211B). This includes:

3Com OfficeConnect 3CRSHPW796 CardBus

Belkin F5D6001 PCI (version 2 only)

Blitz NetWave Point CardBus

D-Link DWL-650 Rev. L1 CardBus

D-Link DWL-520 Rev. C1 PCI

LanReady WP2000 PCI

SMC 2635W CardBus (version 1 only)

TRENDnet TEW-221PC CardBus

Xterasys XN2511B PCI

The atw driver does not yet support cards using revision 0x30 (ADM8211C).

Examples

The following example scans for available networks:

# ifconfig atw0 scan

The following hostname.if(5) example configures atw0 to join network “mynwid”, using WEP key “mywepkey”, obtaining an IP address using DHCP:

join mynwid nwkey mywepkey
inet autoconf

Diagnostics

atw0: failed to tune channel N

The driver failed to tune the radio to a new channel. The radio remains tuned to the old channel.

atw0: atw_si4136_write wrote XXXX, SYNCTL still busy

The driver waited 100ms without seeing an indication that the ADM8211 had finished writing a register on the Si4126 RF/IF synthesizer.

atw0: device timeout

The ADM8211 failed to generate an interrupt to acknowledge a transmit command.