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# 1.4.5.2 bootloader_Trigger Function

## C

    bool bootloader_Trigger(void);

## Summary

Checks if Bootloader has to be executed at startup.

## Description

This function can be used to check for a External HW trigger or Internal firmware trigger to execute bootloader at startup.

This function has to be implemented by the bootloader application to override the WEAK implementation in bootloader.c.

The checks in trigger function should happen before any system resources are initialized apart for PORT. As the same system resource can be re-initialized by the application if bootloader jumps to it and may cause issues.

- External Trigger:

  - Can be achieved by triggering a GPIO_PIN at startup

- Firmware Trigger:

  - Application firmware which wants to execute bootloader at startup needs to fill first n bytes of ram location with a request pattern. The Number of bytes to be reserved for storing the pattern has to be configured in bootloader component configuration in MCC.

      uint32_t *sram = (uint32_t *)BTL_TRIGGER_RAM_START;

      sram[0] = 0x5048434D;
      sram[1] = 0x5048434D;
      sram[2] = 0x5048434D;
      sram[3] = 0x5048434D;

## Precondition

PORT/PIO Initialize must have been called.

## Parameters

None.

## Returns

- True: If any of trigger is detected
- False: If no trigger is detected

## Example

    #define BTL_TRIGGER_PATTERN  0x5048434D

    static uint32_t *ramStart = (uint32_t *)BTL_TRIGGER_RAM_START;

    bool bootloader_Trigger(void)
    {
        // Check for Bootloader Trigger Pattern in first 16 Bytes of RAM to enter Bootloader.
        if (BTL_TRIGGER_PATTERN == ramStart[0] && BTL_TRIGGER_PATTERN == ramStart[1] &&
            BTL_TRIGGER_PATTERN == ramStart[2] && BTL_TRIGGER_PATTERN == ramStart[3])
        {
            ramStart[0] = 0;
            return true;
        }

        // Check for Switch press to enter Bootloader
        if (SWITCH_Get() == 0)
        {
            return true;
        }

        return false;
    }

    void SYS_Initialize()
    {
        NVMCTRL_Initialize();

        PORT_Initialize();

        if (bootloader_Trigger() == false)
        {
            run_Application();
        }

        CLOCK_Initialize();
    }

Rev: G