Ezurio 05W User Manual

WISM SLIP - User Guide

Doc No: SDS_WI001_2V6 Issue No : 2.6
Date : 18th September 2006 Page i

WISM SLIP - User Guide

© 2006 COPYRIGHT Ezurio Ltd
This document is issued by Ezurio Limited (hereinafter called Ezurio) in confidence, and is not to be
reproduced in whole or in part without the prior written permission of Ezurio. The information contained
herein is the property of Ezurio and is to be used only for the purpose for which it is submitted and is not to
be released in whole or in part without the prior written permission of Ezurio.

WISM SLIP - User Guide

Doc No : SDS_WI001_2V6 Page 2

Contents

1. Introduction 1

1.1 Overview ........................................................................................................................ 1

1.2 References..................................................................................................................... 1

1.3 Glossary of Terms.......................................................................................................... 1

2. SLIP Mode Operation 2

2.1 SLIP Mode Command and Data Framing....................................................................... 2

2.1.1 SLIP Overview ............................................................................................. 2

2.1.2 Frame Format ..............................................................................................2

2.1.3 Example Frame............................................................................................ 3

2.2 Command Transactions ................................................................................................. 3

2.2.1 Command Format ........................................................................................3

2.2.2 Response Format ........................................................................................ 3

2.3 UART Signalling............................................................................................................. 3

2.4 Power Management ....................................................................................................... 4

2.4.1 IEEE Power Save Mode............................................................................... 4

2.4.2 Power Save Mode 1..................................................................................... 5

2.4.3 Power Save Mode 2..................................................................................... 5

3. Command Catalogue 6

3.1 UARTMODIFY (baud, length, parity, stop, persist)......................................................... 6

3.2 AUTHENTICATE (flag) ..................................................................................................7

3.3 SECURITY (flag)............................................................................................................ 7

3.4 BSSTYPE (flag) .............................................................................................................7

3.5 ATTACH(“name”) ........................................................................................................... 8

3.6 KEY(“keystring”)............................................................................................................. 8

3.7 SEARCH()...................................................................................................................... 8

3.8 CHANNEL(number)........................................................................................................9

3.9 MACADDRESS()............................................................................................................9

3.10 DETACH()............................................................................................................. 9

3.11 POWERSAVE(flag)............................................................................................... 9

3.12 GETSTATS()......................................................................................................... 10

3.13 GETRSSI()............................................................................................................ 10

4. Response Catalogue 11

4.1 Response Format........................................................................................................... 11

4.2 OK.................................................................................................................................. 11

4.3 ERROR code ................................................................................................................. 12

4.4 SEARCHRESULTS results ............................................................................................ 12

4.5 MACADDRESS address ................................................................................................ 13

4.6 STATISTICS stats.......................................................................................................... 13

4.7 RSSI values ................................................................................................................... 14

WISM SLIP - User Guide

Doc No : SDS_WI001_2V6 Page 1

1. Introduction

1.1 Overview

This document provides a User Guide for the Ezurio WISM module incorporating the SLIP
interface. The module provides a UART interface to the host device which is used to configure
the module operation and then transfer data between the host and the communication end-point
via the wireless interface. The Wireless Lan module is the first in a family of Universal Wireless
(UW) modules from Ezurio which aim to provide the same control and data interface regardless
of the wireless interface being used (Bluetooth, Wireless Lan etc). For this reason the module
must contain all of the necessary elements to allow the transport of data over the selected
wireless interface. In the case of Wireless Lan this means that the module contains the TCP/IP
stack and associated protocols in addition to the Wireless Lan driver. The module takes
responsibility for the packetisation of data from the host prior to transmission and the
serialisation of received packets.

In addition to the above features, Ezurio have implemented a SLIP interface to the module which
allows the transfer of 802.3 packets via the UART. In this mode the internal TCP/IP stack of the
module is disabled and the 802.3 packets are directly interfaced to the top of the Wireless Lan
driver. In addition, because the interface to the module is now packet based, a packet framing
protocol is applied to the data as it is transferred across the UART. To simplify the interface, the
same packet framing protocol is applied to both control and data information when operating in
the SLIP mode. Also, to simplify the interface, the Universal Wireless scripting language method
of control has been replaced by a fixed set of Wireless Lan specific commands that will be used
to configure the module in SLIP mode.

1.2 References

1.3 Glossary of Terms

AP Access Point

MSDU MAC Service Data Unit

RAT Radio Access Technology

SLIP Serial Line Internet Protocol

UW Universal Wireless

WISM SLIP - User Guide

Doc No : SDS_WI001_2V6 Page 2

2. SLIP Mode Operation

The WISM SLIP module provides an interface that allows 802.3 packets to be passed to and
from the module. In this mode the TCP/IP stack is bypassed and the 802.3 packets are
interfaced directly to the Wireless Lan device driver. Due to the packet nature of the data flowing
across the UART a framing protocol is needed to allow packet start and end to be delimited. For
simplicity, the SLIP protocol has been selected for this purpose and is described below.

Given that the data flowing across the interface uses the SLIP protocol, it makes sense for the
commands and responses to use the same protocol.

2.1 SLIP Mode Command and Data Framing

2.1.1 SLIP Overview

SLIP is a simple framing standard for the transmission of IP datagrams over a serial interface
(RFC 1055). SLIP defines an END character (0xC0) and an ESC character (0xDB). The END
character is prepended and appended to the packet to be transferred. Pre-pending the packet
with the END character allows the interface to re-synchronise on the next frame if noise corrupts
a packet.

Given that the END character has special meaning, it is necessary to ensure that the END
character does not appear within the packet payload. To avoid this, any occurrence of the END
character within the payload is escaped (replaced) by two characters, ESC and 0xDC. If the ESC
character is encountered within the packet, then it too is escaped (replaced) with two characters
ESC and 0xDD.

2.1.2 Frame Format

Data and command information transferred across the UART interface is encapsulated in frames
using the SLIP frame structure shown in Figure 1.

Figure 1 UART Frame Format

The fields are as follows:

Header Byte: SLIP frame END byte, set to ‘0xC0’.

Packet Type: Describes the contents of the payload. This byte is coded as follows:

Byte Value Payload Contents

0x01 Command frame. Frame contains a command / response string.

0x02 Data frame. Frame contains an 802.3 frame.

Payload: The format of the payload depends on the Packet Type description. The payload must
have all occurrences of the END and ESC character removed as described in Section 2.1.1.

Footer Byte: SLIP frame END byte, set to ‘0xC0’

WISM SLIP - User Guide

Doc No : SDS_WI001_2V6 Page 3

2.1.3 Example Frame

The following example is a control frame containing a UW command:

2.2 Command Transactions

Commands can be sent to the module at any time. All commands are acknowledged by a
response from the module. The host must not send the next command until the response for the
current command has been received, however, data frames can be sent to or from the module
while a command response is awaited. Responses are sent when the requested command has
been executed. In practice this means that some commands (SEARCH for example) may take a
significant time before the response is returned.

2.2.1 Command Format

Commands are ASCII strings and have the following generic format:

2.2.2 Response Format

Responses are ONLY sent in response to commands from the host. Responses are in ASCII
and are sent as the payload in a SLIP frame. All responses have the following generic format:

The response codes and associated details are described in Section 4.

2.3 UART Signalling

UART control signals are used at the host interface to indicate the status of the module, as
outlined below:

Signal Name Module Input /

Output

Function