Finding Open WiFi with Matchport

The Lantronix Matchport is an embedded WiFi module used to gateway serial information to the Internet via 802.11.b/g wireless. Normally it must be configured to work with a specific WiFi network, which means that can’t roam from place to place without being manually reconfigured. While this is fine for a device that will be installed in one fixed location, it’s not very helpful for anything portable. For example, a networked toy should still function at your friend’s house, in a hotel room or even at the park.

Technically it should be possible to have the Matchport seek out and connect to unsecured WiFi networks. Here’s my concept:

A microcontroller connected to the Matchport via serial:

• resets the Matchport, then sends “zzz” to put it into monitor mode
• issues the SA command to scan for networks and seeks the first instance of “NONE” [for encryption], followed by the SSID
• reads in this SSID
• resets the Matchport again and sends “xxx” to put it into configuration mode
• issues the 4 command followed by the proper number of carriage returns
• issues the SSID into the correct field
• issues another series of carriage returns and a 9 command to exit and save the changes

At this point it can test the connection and see if it works. On failure it could try resetting again a few times, then repeat the above sequence and seek the second instance of “NONE” to get the next open network. Not sure how reliable the whole thing would be, but it should work at least sometimes. Other Lantronix products, such as the WiPort should work the same way.