LR1110
User Manual
Rev.1.0
UM.LR1110.W.APP
March 2020
85 of 130
Semtech
time the LR1110 spends in Preamble Search mode in case no Wi-Fi activity is detected in a given channel. The capture of a
WiFi packet can only be done if a WiFi preamble is detected during the Preamble Search window.
The scanned results are accumulated into the LR1110 memory over the successive Wi-Fi passive scannings on the various
Wi-Fi channels and Wi-Fi types. Up to 32 different MAC addresses total are stored in the retention RAM memory, therefore
they can be read at any time before the LR1110 goes to Sleep mode without retention or Powerdown. Above 32 MAC
addresses, no additional results are retrieved. Please note that sending a new WifiScan ( ) command automatically clears
the previous results.
Although at least 1 MAC address is necessary to determine an approximate geolocation, it is a good approach to gather 3
MAC addresses or more to ensure a successful device geolocation and increase its precision. Therefore, performing Wi-Fi
passive scanning on various channels might be necessary, depending on the Wi-Fi traffic in the environment.
10.2 WifiScan
The command
WifiScan( )
allows capturing the Wi-Fi packets on the RFIO_HF pin:
•
Wi-Fi Type
defines the type of the 801.11 signal to be scanned:
0x01: Wi-Fi 802.11b type
0x02: Wi-Fi 802.11g type
0x03: Wi-Fi 802.11n type
0x04: All signals: Wi-Fi b, then Wi-Fi g/n on the same channel
•
ChanMask
defines which Wi-Fi channels to be scanned:
[0 0 Ch14 Ch13 Ch12 Ch11 Ch10 Ch9 Ch8 Ch7 Ch6 Ch5 Ch4 Ch3 Ch2 Ch1]
channel bit at 1 indicates that this channel must be scanned
•
AcqMode
indicates the
WifiScan
acquisition mode:
0x01: Beacon search mode. Use only the Wi-Fi beacons to extract the MAC addresses.
0x02: Beacon and Packet search mode. Use both the Wi-Fi beacons and WI-Fi data packets to extract the MAC
addresses.
Other values are RFU
•
NbMaxRes:
maximum total number of different MAC addresses wanted as a result for all scans on the various channels
and Wi-Fi types (must be inferior or equal to 32). If this number is reached the passive scanning is stopped. If a MAC
address already present in the result structure is detected a second time with a different RSSI value, then the new
result is ignored.
Table 10-1: WifiScan Command
Byte
0
1
2
3
4
5
6
7
8
9
10
Data
from
Host
0x03
0x00
Wi-Fi
Type
Chan
Mask
(15:8)
Chan
Mask
(7:0)
Acq
Mode
Nb
Max
Res
Nb
Scan
Per
Chan
Time
out
(15:8)
Time
out
(7:0)
Abort
On
Time
out
Data
to
Host
Stat1
Stat2
IrqStatus
(31:24)
IrqStatus
(23:16)
IrqStatus
(15:8)
IrqStatus
(7:0)
0
0
0
0
0
