#68-D: integer conversion resulted in a change of sign

warning:  #68-D: integer conversion resulted in a change of sign
NVIC_InitStructure.NVIC_IRQChannel = SysTick_IRQn;          

好像意思是说
NVIC_InitStructure.NVIC_IRQChannel
SysTick_IRQn
这2个数据类型不一样,一个有signed一个unsigned?

SysTick_IRQn是Cortex-M3处理器异常，不归NVIC管，不是一个系统的，NVIC只管STM32外设上的中断。所以故意把它定义为负数(本人臆测的)，使用sys-tick中断，调用一下SysTick_Config()函数就OK了，sys-tick是在那里使能的。

unsigned 与 signed 类型的默认转换。如果不是负数或很大的数，一般就不会有问题。

void SysTick_Configuration(void) {     // Initialize SysTick timer and set period at 100us.      // HCLK (=SYSCLK)=120MHz     // Set SysTick clock source to HCLK/8 = 15MHz     SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8);                        // SysTick clock = 120MHz/8 = 15MHz (CTRL reg. Clear Bit 2)       SysTick->LOAD = (SYSTICK_US * SYSTICK_CLK_MHz);                             // Set SysTick period     SysTick->VAL = 0;                                                            // Clear SysTick counter     SysTick->CTRL |= (SysTick_CTRL_ENABLE_Msk | SysTick_CTRL_TICKINT_Msk);        // Start SysTick timer with tick interrupt enabled       // It's not possible to use the following function to setup SysTick within the NVIC module because SysTick is a core function.     //    NVIC_InitStructure.NVIC_IRQChannel = SysTick_IRQn;     //    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;                // TIM1 (Metronome) Preemption Priority = 2     //    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;      //    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;     //    NVIC_Init(&NVIC_InitStructure);       // Use the following Coretex M3 function instead:     NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1);                 //      // Refer to http:-//blog.csdn.-net/sunjiajiang/article/details/7741715 for details regarding pre-emption and subpriority      

还有，库文件中的东西不要改。ST的库文件其实已经是只读的了，就是为了禁止修改。