Explanation of STM32 NVIC configuration

When configuring the interrupt priority of each peripheral, most development boards used for learning are used to configure the NVIC group in the initialization file of each peripheral. For example, the NVIC configurations of ADC and Usart are as follows:

In ADC:

void ADC_NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);

NVIC_InitStructure.NVIC_IRQChannel =ADC1_2_IRQn; // Enable ADC_Channel8 interrupt

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);   

}

Usart:

void NVIC_Configuration(void)

{

  /* Structure declaration */

  NVIC_InitTypeDef NVIC_InitStructure;

  /* Configure the NVIC Preemption Priority Bits */  

  /* Configure one bit for preemption priority */

  /* The priority group specifies the number of bits used for preemption priority and response priority. Here, it is 0, 4 

  Group 0: Preemption priority occupies 0 bits, response priority occupies 4 bits

  Group 1: Preemption priority occupies 1 bit, response priority occupies 3 bits

  Group 2: Preemption priority occupies 2 bits, response priority occupies 2 bits

  Group 3: Preemption priority occupies 3 bits, response priority occupies 1 bit

  Group 4: Preemption priority occupies 4 bits, response priority occupies 0 bits  

  */       

  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);    

  NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; //Set serial port 1 interrupt

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; //Preemption priority 0

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; //Subpriority is 0

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //Enable

  NVIC_Init(&NVIC_InitStructure);

}

But in fact, this configuration is unreasonable, that is, if the interrupt groups configured by the two NVICs are different, if one of the peripherals references a priority value other than that allowed by the last configured interrupt group, a conflict may occur. After discussing with the teacher, he believes that if the previously initialized priority is unreasonable compared to the value set by the later priority group, the previous interrupt may not be responded to, BUT...

When I was experimenting, I found that no matter how I changed the order of these two priority configurations, it seemed to have no effect on the results of my program.

Of course, the teacher's suggestion is to create a systemconfig file in the project to configure the interrupt priority group and clock, that is, the interrupt priority group configuration only appears once