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Have a question about Micrium's embedded software? Ask our Expert, Matt Gordon

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Matt Gordon

Matt Gordon is a senior applications engineer at Micrium.  He began his career developing device drivers, kernel ports, and example applications for Micrium's customers.  Drawing on this experience, Matt has written multiple articles on embedded software.  He also heads Micrium's training program and regularly teaches classes on real-time kernels and other embedded software components.  Matt holds a bachelor's degree in computer engineering from Georgia Tech, Georgia in the USA.


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  • Hi Matt, I am a newbie to RTOS and i have started with uCOS III.

     

     

              OSSemCreate(&MySem,                                                                                 // Creating Semaphore

                           "SerialPortSemaphore",

                                                                1,

                                                                &err);

     

    I want to make my semaphore to enable the UART, but i dont know how. I have made another function that enables the UART and this function is called from the switch statement just after the OSSemPend(...).

    Please help me with this, or just show me an example to create and use a semaphore.

     

    Best Regards.

  • in reply to Former Member

    Typically, the purpose of a semaphore used with a UART is to signal the reception of data.  The semaphore post takes place in the UART's receive ISR, and the pend occurs in the code responsible for processing the data.  This setup is illustrated in the below example.  (I've omitted the semaphore creation code from this example, since it would simply involve the function call named above.)

     

    void  UART_ISR (void)

    {

        /* Clear interrupt flag */

        OSSemPost (&AppSemUART, OS_OPT_POST_1, &err);

    }

     

    void  UART_Task (void *p_arg)

    {

        while (1) {

            OSSemPend(&AppSemUART, OS_CFG_TICK_RATE_HZ, OS_OPT_PEND_BLOCKING, 0, &err);

            /* Read from buffer and process data */

        }

    }

     

    Regards,

     

    Matt

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  • in reply to Former Member

    Typically, the purpose of a semaphore used with a UART is to signal the reception of data.  The semaphore post takes place in the UART's receive ISR, and the pend occurs in the code responsible for processing the data.  This setup is illustrated in the below example.  (I've omitted the semaphore creation code from this example, since it would simply involve the function call named above.)

     

    void  UART_ISR (void)

    {

        /* Clear interrupt flag */

        OSSemPost (&AppSemUART, OS_OPT_POST_1, &err);

    }

     

    void  UART_Task (void *p_arg)

    {

        while (1) {

            OSSemPend(&AppSemUART, OS_CFG_TICK_RATE_HZ, OS_OPT_PEND_BLOCKING, 0, &err);

            /* Read from buffer and process data */

        }

    }

     

    Regards,

     

    Matt

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