Dimming application using an STM32 microcontroller

AN2841

18/31

Figure 16.

Real signals: timer interrupt + DMA transfer + DMA interrupt model

Step "1" in Figure 16 is not necessary, but it is used for a better visualization of the tracking

of signals on the oscilloscope.

Example of C code of DMA and timer interrupt routine: interrupt + DMA +

interrupt approach

void SysTickHandler(void)

{

LE_LOW();(Step 1)

LE_HIGH();

depth+=4;

if(depth > 0x400)

depth = 0;

DMA_Channel3->CCR &= CCR_ENABLE_Reset;

DMA_Channel3->CNDTR = 0x04;

DMA_Channel3->CMAR = ((u32) (LookUp))+depth;

DMA_Channel3->CCR |= CCR_ENABLE_Set; (Step 2)

DMA_Channel3->CCR |= DMA_IT_TC;

LE_LOW();

}

void DMAChannel3_IRQHandler(void)(Step 5)

{

while(!SPI_GetFlagStatus(SPI1, SPI_FLAG_TXE));(Step 6)

LE_HIGH();(Step 7)

LE_LOW();

DMA_ClearITPendingBit(DMA_IT_GL3);

}