There are two Wi-Fi interfaces available for use with WiConnect, a wlan client (802.11 STA) interface and a softAP (802.11 AP) interface. Both interfaces share the same physical Wi-Fi radio and antennas. To set the Wi-Fi transmit power for both interfaces, use the common wlan.tx_power variable. Likewise, to set the antenna used by both interfaces, use the common wlan.antenna variable.
WLAN Client Interface
The wlan client interface enables WiConnect to join with a Wi-Fi access point at home, work or in-between. It is possible to use the wlan and softap interfaces concurrently, however these interfaces share the Wi-Fi radio and hence must operate on the same Wi-Fi radio channel in concurrent mode. The wlan interface has priority, and if the wlan interface starts on a different channel to the softap interface, the softap channel switches to the wlan channel.
WiConnect provides various commands and variables to configure the wlan interface. See the documentation for wlan commands and wlan variables. An overview of WLAN functionality is provided in the following sections.
Scanning for Networks
There are two methods to scan for networks in range, active scanning and passive scanning. Active scanning involves the Wi-Fi module actively transmitting 802.11 probe request packets. When a Wi-Fi Access Point receives a probe, it replies with an 802.11 probe response. Passive scanning on the other hand avoids actively transmitting, and the Wi-Fi module simply listens for Wi-Fi Access Point beacons for a period of time on each channel scanned.
Each of the parameters discussed in the preceding paragraph (plus more) are configurable with WiConnect. To specify the channels to scan, use the wlan.scan.channel_mask variable. The scan type (active or passive) can be set using the wlan.scan.type variable. The time spent listening on each channel, in active and passive scan mode respectively, is configurable using the wlan.scan.active_dwell and wlan.scan.passive_dwell variables. In active mode, the number of 802.11 probe requests is configurable using wlan.scan.num_probes.
And finally, to initiate a scan for Wi-Fi networks in range, use the wlan_scan command.
Joining a Network
To join a network manually, set the wlan.ssid and wlan.passkey variables to match the network name and network password the module is attempting to join. If your application is sensitive to latency or power, you should also consider customizing the number of join retry attempts with the wlan.join.retries. WiConnect supports all SOHO security types including Open, WEP, WPA & WPA2 together with mixed modes. If you are planning to use WEP (and we sincerely hope you are not since WEP IS NOT SECURE), please read the instructions in wlan security.
To hide the passkey after it has been set, simply set the wlan.hide_passkey variable. After the passkey is hidden, it is no longer possible to read the passkey until a factory reset is performed. This stops an attacker learning the network password by physically acquiring a product with an ACKme module running WiConnect.
If the application requires the module to auto-join a network after boot up, set the wlan.auto_join.enabled variable. The number of automatic retry attempts and the delay between automatic retries is configurable with the variables wlan.auto_join.retries and wlan.auto_join.retry_delay.
Once the module is joined to a Wi-Fi network, the received signal strength (signal level) of the Wi-Fi Access Point is available with the wlan_get_rssi command.
If the signal strength of the Wi-Fi Access Point the module is joined with drops too low, the module attempts to scan for (and roam to) another known network in range. The received signal level at which roaming is initiated is configured using the wlan.roam.threshold variable. While the module is roaming on other radio channels, it may miss packets on the home channel. Depending on your application, it may be necessary to modify one or more of the wlan scan variables discussed in the Scanning for Networks section to minimize packet loss during roaming.
Access Point (SoftAP) Interface
The softAP interface enables a Wi-Fi client such as a notebook, smartphone or tablet to join with WiConnect. The softap interface is primarily controlled with the softap variables.
SoftAP features include ...
- Auto start on reboot
- Wi-Fi radio channel selection
- Control of interface settings such as IP address range, DHCP server, DNS redirect server
- Options to adjust AP name, password and URL
- Combined use with a web server for provisioning of the wlan interface
- Plus more ...