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Friday, September 14, 2012

Roving Networks RN XV - Wifly module

In the previous post I illustrated a basic way to interface the wifly module to the MSP430G2 using the uart.
As I already anticipated in that post, the method could be improved, but for that we need to dig in a bit into the features of this module.

The wifly has the ability to store configurations, this means that we can pre-set all the needed parameters and we can avoid to send them from the mcu via uart.

Using an FTDI cable I connect to the module and set the config pars :

$$$  (to enter in command mode)
set wlan auth 3 
set wlan ssid myssid
set wlan phrase mypwd
set wlan channel 0   (0 means autoscan)

The configuration is now saved and it will be automatically loaded at each reboot / power up.
Once these parameters are set, to join the ssid, we will just need to issue the command


However we could even do better than that, in fact, if we set the auto join function to "1" (which btw is the default) the wifly will automatically try to join the ssid at each reboot.

set wlan join 1

Cool, not much to do for our mcu now, eh?
Just wait, it actually gets even better.

Fine, we are associated with the ssid, we got an ip address etc, now we need to establish a tcp connection to a remote server.
I quote from the RN XV user manual :

set ip proto 18 //enable html client
set dns name //name of your webserver
set ip address 0 // so WiFly will use DNS
set ip remote 80 // standard webserver port
set com remote 0 // turn off the REMOTE string so it does not interfere with the post

You guessed that, you can save this too in the internal config!


To make the connection the command would be:
or inline you can send open 80
The user’s microprocessor should write to the uart:
GET /ob.php?obvar=WEATHER \n\n

So, finally this makes things way easier, but it's not the end of the story...
What if we could check from a gpio pin if the wifly is associated, then raise another gpio to ask it to connect to the remote tcp port and finally get from a third gpio if it successfully connected?

Yup, that's another nice feature which is actually available.
The specific gpio pins are the 4,5 and 6 and must be configured to be used in this way.

set sys iofunc 0x70 // enable alternate function for GPIO 6, 5 and 4

With all this set and saved in the configuration, at power on the wifly module will try to associate to the ssid. once it is ready to perform a tcp connection it will raise gpio4 (which we will check from our mcu).
At that point, when we need to contact the remote server, we will raise the gpio5 and check gpio6 to verify that the connection was established.
At that point, if we are contacting a web server, we will send the GET request through the uart and will receive the answer from there.

... and we did not even need to enter in command mode!

Nice eh?
Will implement this with the launchpad in the next days.

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