How to use beagleboard peripheral with simulink ?

Issue I :- I am using MATLAB R2012b. I am able to run simulink model on target device (BeagleBoard xM). I want to develop an application to capture a single image (like a photograph ) but camera module is continuously sending video data. how could i stop the video and save a single photograph?

 Issue II :-  There are only few blocks available for Beagleboard XM in
simulink. There is no block for USB, UART (serial port), User switch, and
Other GPIO's so how one can access those peripheral in simulink?