Problem with overlapping of S-functions in embedded program

Hello to all,

I have a problem with my project of an autopilot for an UAV. I'm using a launchpad Tiva C and I'm making an embedded program.

The problem is that I'm using a GPS (by UART), Radio Link (by UART) and an IMU (by I2C) and in Simulink I made a s-function in C for each hardware to read the data.

When I tested each hardware separately all works fine, but when I tried to run all the blocks at the same time with these samples times:

-GPS every 1 sec

-IMU every 0.01sec

-Radio link every 3 sec

The program hangs in a few seconds, so I suppose that the problem is that the first S-functions initiate but the simulink program continue and initiate the second S-function so the S-function overlap and get blocked, so I decided to use subsystems with diferent triggers but the same occurs. I tried to use function caller with mux but the same.

The problem is because the diferent rate of calling for each s-functions in some moment the calling will be in the same time.

So I need to find the way to run one s-function and wait it to finish the process and then run the next, but I don't have idea of how do that.

Thanks Regards