1.4 Adding Application Logic to Secure Project

To develop and run the application, follow these steps:

  1. Open the main.c file of the Secure project and add the following application logic. Add the following code to register RTC event handlers for a 500 ms compare event. RTC_Timer32CallbackRegister (rtcEventHandler, 0); and the following code for the EIC callback event handler for the switch press event EIC_CallbackRegister (EIC_PIN_12, sw0_eventHandler, 0); in the main() function and SYS_Initialize (NULL) function below:
    RTC_Timer32CallbackRegister(rtcEventHandler, 0);
EIC_CallbackRegister(EIC_PIN_12, sw0_eventHandler, 0);
  2. Add the line of code to call the RTC_Timer32Start() function after registering the callback event handlers.
    Figure 1-16. Adding Application Logic to Register Callback Event Handlers
  3. Implement the registered callback event handlers for secure peripherals by adding the following code.
    static void sw0_eventHandler(uintptr_t context)
{
    changeSamplingRate = true;
}

static void rtcEventHandler (RTC_TIMER32_INT_MASK intCause, uintptr_t context)
{
    if (intCause & RTC_TIMER32_INT_MASK_CMP0)
    {
        isRTCTimerExpired = true;
    }
}
    Figure 1-17.  Adding Application Logic to Implement the Registered Callback Event Handlers
  4. In the secureApp() function, add the application logic of toggling LED at different rates of 500 ms, 1s, 2s, and 4s whenever there is a switch press on the board by the user before the main() function in Secure Project.

    The complete secure functionality must run in the while(1) super loop of the main() function in main.c file of Secure Project.

    Figure 1-18. Adding Application Logic to Enter Secure App Functionality
  5. Under Source Files > trustZone, in the nonsecure_entry.c file, implement the Non-Secure callables below to access and request the secure application from the Non-Secure application.
    bool __attribute__((cmse_nonsecure_entry)) readUartTxData(uint8_t *lcluartTxBuffer)
{
    bool localSecureUartStatus = readUartTxStatus;
    if(localSecureUartStatus == true)
    {
        memset((char*)lcluartTxBuffer, 0x00, 100);
        memcpy(lcluartTxBuffer, uartTxTempBuffer, strlen((const char *)&uartTxTempBuffer[0]));
        readUartTxStatus   = false;
    }
    return (localSecureUartStatus);
}

void __attribute__((cmse_nonsecure_entry)) secureAppEntry(void)
{
    secureApp();
}
    Figure 1-19. Adding Application Logic to Implement the NSCs