Dear all,
I got a little confused about the optical flow NVIC configuration.
Code in usb_bsp.c:
void USB_OTG_BSP_EnableInterrupt(USB_OTG_CORE_HANDLE *pdev)
{
NVIC_InitTypeDef NVIC_InitStructure;
**NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);**
NVIC_InitStructure.NVIC_IRQChannel = OTG_FS_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
This sets the priority group as 1, so the preemption could only be 0 or 1. However in DCMI.c:
void dma_it_init()
{
NVIC_InitTypeDef NVIC_InitStructure;
/* Enable the DMA global Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream1_IRQn;
**NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 5;**
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
DMA_ITConfig(DMA2_Stream1, DMA_IT_HT, ENABLE); // half transfer interrupt
DMA_ITConfig(DMA2_Stream1, DMA_IT_TC, ENABLE); // transfer complete interrupt
}
It just sets this param to 5. I got confused why it can still work by falsely setting the NVIC priority.