DMA (STM32), dmastm32

DMA (STM32), dmastm32

1. DMA: data memory access // actual memory storage

Note: CPU interference is not required when DMA is used.

2.

① Memory (Defined variables) --- peripherals (registers );

② Memory --- memory

③ Peripherals --- peripherals (registers of One peripheral to another)

3.

STM32 has two DMA controllers

4. Example: (memory to peripherals, Serial Port 1 tx dma)

 1 void USART1_DMA_Config(void) 2 { 3         DMA_InitTypeDef DMA_InitStructure; 4      5         /*Open the DMA clock*/ 6         RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE); 7  8         /*Set the DMA source: serial port data register address*/ 9         DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_DR_Base;       10 11         /*Memory address,(A pointer to the variable transmission)*/12         DMA_InitStructure.DMA_MemoryBaseAddr = (u32)SendBuff;13 14         /*Direction:From memory to the peripherals*/        15         DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;    16 17         /*Transmission size:DMA_BufferSize=SENDBUFF_SIZE*/    18         DMA_InitStructure.DMA_BufferSize = SENDBUFF_SIZE;19 20         /*It does not increase peripheral address*/        21         DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; 22 23         /*Memory address since the increase*/24         DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;    25 26         /*A peripheral unit of data*/    27         DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;28 29         /*Memory data unit:8bit*/30         DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;     31 32         /*The DMA mode: cycle*/33         //DMA_InitStructure.DMA_Mode = DMA_Mode_Normal ;34         DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;     35 36         /*priority:medium*/    37         DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;  38 39         /*Memory to memory transmission is prohibited*/40         DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;41 42         /*Configuration of the channel 4*/           43         DMA_Init(DMA1_Channel4, &DMA_InitStructure);        44         45         /*enable DMA1_Channel4*/46         DMA_Cmd (DMA1_Channel4,ENABLE);                    47         //DMA_ITConfig(DMA1_Channel4,DMA_IT_TC,ENABLE);  //Configuration after completion of the DMA interrupt48 }

① Usart0000tx is mounted to Channel 4 of DMA1 (each DMA has 7 channels, corresponding to different peripherals)

② The ninth line of the program source (source)

That is, the source address (peripheral address)

1 # define USART1_DR_Base 0x40013804 // 0x40013800 + 0x04 = 0x40013804

How can we calculate it?

Please refer:

 

What is the base address?

 

Therefore, the data register address of Serial Port 1:

// 0x40013800 + 0x04 = 0x40013804

③ Memory address, custom Array

Direction 4: memory to peripherals

⑤ Transmission size: 5000 bytes

6. If the peripheral address is not increased, the memory address is automatically increased, and 5000 bytes are sent cyclically.

7. Sending mode: Normal: the sending of 5000 bytes is finished, and circular is sent cyclically.

Priority: If several peripherals in a program have applied for a DMA request at the same time, select

Bytes disables memory-to-memory transmission.

4. Check the main function.

Uint16_t I;/* Filling is going to send data */for (I = 0; I <SENDBUFF_SIZE; I ++) {SendBuff [I] = 'a ';} /* USART1 sends a TX request to DMA */USART_DMACmd (USART1, USART_DMAReq_Tx, ENABLE);/* the CPU is idle at this time, you can do other things * // LED At the same time scintillation for (;) {LED1 (ON); Delay (0 xFFFFF); LED1 (OFF ); delay (0 xFFFFF );}

Note)
　

DMA in M3 can only be triggered by software, and some chips can be triggered by external pulses;

 

DMA channel in STM32

Well, you should have modified the stm32 Firmware Library function.
DMA_Channel_TypeDef * refers to the pointer of DMA_Channel_TypeDef, which points to an address.
DMA_CHx should be a macro definition, which defines this address.
The x value indicates the DMA channel number. Depending on the chip, there may be 1 ~ 7.
To understand the macro definition, use goto difinition to view the macro definition.

Follow-up

When configuring DMA for STM32: Error: L6218E: Undefined symbol DMA_Cmd (referred from maino) keil 412

Add XXX_DMA.C to the StdPeriph_Driver folder of the project.