ESP8266 datasheet(106/117 Pages) ESPRESSIF

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14. Sniffer Introduction

14.

Sniffer Introduction

14.1. Sniffer Introduction

ESP8266 can enter promiscuous mode (sniffer) and capture IEEE 802.11 packets in the air.

The following HT20 packets are support:

•

802.11b

•

802.11g

•

802.11n (from MCS0 to MCS7)

•

AMPDU types of packets

The following are not supported:

•

HT40

•

LDPC

Although ESP8266 can not completely decipher these kinds of IEEE80211 packets

completely, it can still obtain the length of these special packets.

In summary, while in sniffer mode, ESP8266 can either capture completely the packets or

obtain the length of the packet:

•

Packets that ESP8266 can decipher completely; ESP8266 returns with the

- MAC address of the both side of communication and encryption type and

- the length of entire packet.

•

Packets that ESP8266 can only partial decipher; ESP8266 returns with

- the length of packet.

Structure RxControl and sniffer_buf are used to represent these two kinds of packets.

Structure sniffer_buf contains structure RxControl.

struct RxControl {

signed rssi:8;

// signal intensity of packet

unsigned rate:4;

unsigned is_group:1;

unsigned:1;

unsigned sig_mode:2;

// 0:is not 11n packet; non-0:is 11n

packet;

unsigned legacy_length:12; // if not 11n packet, shows length of

packet.

unsigned damatch0:1;

unsigned damatch1:1;

Espressif

! /!

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2017.05

ESP8266 Datasheet(PDF) 106 Page - ESPRESSIF SYSTEMS (SHANGHAI) CO., LTD.

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