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(1) The application must declare a semaphore as a variable of type OS_SEM. This variable will be referenced by other semaphore services.

(2) You create a semaphore by calling OSSemCreate() and pass the address to the semaphore allocated in (1). The semaphore must be created before it can be used by other tasks. Here, the semaphore is initialized in startup code (i.e., main()), however it could also be initialized by a task (but it must be initialized before it is used).

(3) You can assign an ASCII name to the semaphore, which can be used by debuggers or µC/Probe to easily identify the semaphore. Storage for the ASCII characters is typically in ROM, which is typically more plentiful than RAM. If it is necessary to change the name of the semaphore at runtime, you can store the characters in an array in RAM and simply pass the address of the array to OSSemCreate(). Of course, the array must be NUL terminated.

(4) You specify the initial value of the semaphore. You should initialize the semaphore to 1 when the semaphore is used to access a single shared resource (as in this example).

(5) OSSemCreate() returns an error code based on the outcome of the call. If all the arguments are valid, err will contain OS_ERR_NONE. Refer to the description of OSSemCreate() in Appendix A, µC/OS-III API Reference for a list of other error codes and their meaning.