stm32 (two) stm32 interrupt priority setting

stm32 priority
    1. Priority level:
      STM32 users can assign 16 levels of priority, that is, the upper four bits of the priority register NVIC->IP[x] are used to represent the priority of each interrupt.
   
    2. Priority group:
      In STM32, the priority of an interrupt is divided into: preemption priority and sub-priority.
      When making a priority judgment, the preemption priority is compared first and then the sub-priority is compared.
      In the firmware library, variables are used to represent the preemption priority and sub-priority respectively:
      NVIC_InitTypeDef.NVIC_IRQChannelPreemptionPriority; (preemption priority)
      NVIC_InitTypeDef.NVIC_IRQChannelSubPriority; (sub-priority)
      
      The priority group is the boundary between the preemption priority and the sub-priority:
      for example, if the priority group is set to 0x05, it means that the priority of each interrupt starts from the 5th bit as the boundary, and the upper two bits [6:7] are the preemption priority
      . The second bit is [5:4], which represents the sub-priority.
      
      Example:
      //Call the priority group setting function and set the priority to 0x05.
      .....
      NVIC_SetPriorityGrouping(5);
      .....
      //Here, it is explained that the 7th and 6th bits of a priority register (NVIC->IP[x]) represent the preemption priority. 5 and 4 represent the priority.   
      ......
      NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
      NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
      NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
      NVIC_Init(&NVIC_InitStructure);   
      .......
      //Here is the priority setting: From the above settings, we can know that the preemption priority and sub-priority range are both 3~0;
      //Then the priority of an interrupt is set