1.5 Adding Application Code to Non-Secure Project

  1. In the main() function below SYS_Initialize() add the following code to register callback event handlers.
    DMAC_ChannelCallbackRegister(DMAC_CHANNEL_0, usartTxDmaChannelHandler, 0);
  2. Implement the registered callback event handler before the main() function.
    static void usartTxDmaChannelHandler(DMAC_TRANSFER_EVENT event, uintptr_t contextHandle)
{
    if (event == DMAC_TRANSFER_EVENT_COMPLETE)
    {
        isUSARTTxComplete = true;
    }
}
  3. Remove SYS_Tasks( ); function call and replace with the below code to enter the Secure functionality from this Non-Secure application inside the while loop.
        while ( true )
    {
        if (readUartTxData(nonSecureUartTxBuffer) == true)
        {
        /* Maintain state machines of all polled MPLAB Harmony modules. */
            DMAC_ChannelTransfer(DMAC_CHANNEL_0, nonSecureUartTxBuffer, \
                    (const void *)&(SERCOM3_REGS->USART_INT.SERCOM_DATA), \
                    strlen((const char*)nonSecureUartTxBuffer));
        }
        secureAppEntry();
    }
    Figure 1-20. Adding Application Logic to Enter Secure Functionality from Non-Secure App
    Add the following code snippet to include the header files and declaration of variables used in the Non-Secure main.c file.
    #include <stdio.h>
#include <string.h>
#include "trustZone/nonsecure_entry.h"

static volatile bool isUSARTTxComplete = false;
static volatile bool isUSARTRxComplete = false;
static uint8_t nonSecureUartTxBuffer[100] = {0};
  4. In the nonsecure_entry.h file, available under Header Files > trustZone, add the following code by declaring NSCs with extern keyword to access and request the Secure application from the Non-Secure application.
    Note: Delete the generated template code and add the following code.
    extern bool readUartTxData(uint8_t *lcluartTxBuffer);
extern void secureAppEntry(void);
    Figure 1-21. Global NSCs to Access and Request Secure App from Non-Secure App