How to reload the same firmware on the Neo M4 without a reboot

Reloading M4 without rebooting on the UDOO Neo


Most of the time I have to modify and reload firmware on the M4 many times during a debug session, i.e adding debug code or features etc, and each time when reloading firmware the Neo must reboot each time.  This gets old; plus all of the time wasted.

So, what is causes the firmware not to be reloaded? Well that is simple, it is the memory protection setup on the RDC, one simple way to to reload firmware to turn off the RDC protection, another way, just add a compile option and not enable RDC memory protection.

For MQX, it is in the init_hardware.c file, function void rdc_init_memory(void) so, I added a simple #ifdef and allows the code to be reloaded.

void RDC_memory_init(void)
{
    uint32_t start, end;
#if defined(__CC_ARM)
    extern uint32_t Image$$VECTOR_ROM$$Base[];
    extern uint32_t Image$$ER_m_text$$Limit[];
    extern uint32_t Image$$RW_m_data$$Base[];
    extern uint32_t Image$$RW_m_data$$Limit[];

    start = (uint32_t)Image$$VECTOR_ROM$$Base & 0xFFFFF000;
    end = (uint32_t)(Image$$ER_m_text$$Limit + (Image$$RW_m_data$$Limit - Image$$RW_m_data$$Base));
    end = (end + 0xFFF) & 0xFFFFF000;
#else
    extern uint32_t __FLASH_START[];
    extern uint32_t __FLASH_END[];

    start = (uint32_t)__FLASH_START & 0xFFFFF000;
    end   = ((uint32_t)__FLASH_END + 0xFFF) & 0xFFFFF000;
#endif
#if _DEBUG_
#pragma message "Turned off memory protection"
#else
    RDC_SetMrAccess(RDC, rdcMrMmdc, start, end, (3 << (BOARD_DOMAIN_ID * 2)), true, false);    
#endif
}

When compiling just define _DEBUG_ and  load the app.