Scan
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SWRU455A – February 2017 – Revised March 2017
Copyright © 2017, Texas Instruments Incorporated
WLAN
updated, or removed in case of aging). Scan results can include up to 30 entries. Each entry includes
the following parameters:
–
SSID
–
BSSID RSSI
–
Security type and cipher (hidden is part of the type)
–
Channel
If the scan policy is not enabled, calling to sl_WlanGetNetworkList triggers a one-shot scan (this action
does not change the scan policy). In that case, and in any other case in which the results are not ready
yet (such as when the device has just initialized and the scan results are not ready yet),
sl_WlanGetNetworkList should be called again to retrieve the results.
An example of getting scan results from index 0 to 29:
SlWlanNetworkEntry_t netEntries[30];
_i16 resultsCount = sl_WlanGetNetworkList(0,30,&netEntries[0]);
4.7.3 Usage
Scan can be used to find nearby networks before issuing a connection command.
4.7.4 Miscellaneous
•
Scan policy configuration is persistent according to the system-persistent configuration, except for Wi-
Fi Direct mode, where the scan policy cannot be persistent.
•
In Wi-Fi Direct mode, setting the scan policy scans only Wi-Fi Direct devices.
•
Scan runs regardless of the connection state (runs in disconnect mode as well).
•
Scan results are being updated while reading them, so when trying to retrieve specific indexes,
duplicates and other problems may occur.
•
The scan results are not used by the system, but they can be changed by some activities (for example,
the connect activity does not use existing results in the table before it starts a new scan, but the table
is changed during the connection process).
•
If more than one network has the same SSID, but different BSSID, each BSSID is stored in a different
entry.
•
When the scan policy is enabled during the connection scan, the scan policy is activated only after the
connection scan is done (after a successful connection, disconnect command, connection policy
change, or profile deletion), because the connection scan has a higher priority.
4.8
Calibrations
The SimpleLink device performs calibration of the Wi-Fi physical layer. The system supports three
different calibration modes to optimize this process with the required use case. The default calibration
mode is triggered. Setting the calibration mode can be done only by the Image Creator tool during the
creation of the image.
•
Normal calibration mode is used to achieve the best RF performance, or when the environment of the
device is prone to changes (temperature changes).
•
Triggered calibration mode is used for lowest power consumption. Calibrations are done once on the
first boot, and kept for consecutive boots. Recalibration is done on TX power change, or during the
restore-to-factory process.
•
One-time calibration mode is similar to Triggered mode, but recalibration is never done under any
circumstances. One-time is used when the system power source is not able to handle the peak
calibration current. In this mode, user actions that trigger recalibration in Triggered mode are blocked.
NOTE:
For low power applications, TI recommends choosing Triggered mode over One-Time
calibration mode, unless current peak limit is an absolute constraint. Triggered mode does
not issue calibrations unless absolutely necessary, or manually triggered.