Solve the bug https://github.com/fboris/QuadrotorFlightControl/issues/39 more properly
I think the problem we encountered is not the delay issue. Because we read the value which was not initialized, this issue might cause the problem. I let the statusReport_task suspend at startup. After system have done correction, statusReport_task will resume.
We will not use timer semaphore anymore
Stop using tick hook and software timer

Removing tick hook will improve the efficiency of the RTOS kernel.
And We will not use software timer now.
Reference:
http://www.freertos.org/FreeRTOS-for-STM32F4xx-Cortex-M4F-IAR.html
Merge pull request #40 from zxc2694/master

SD card can work.