STM32 DMA receives serial port data

 

• adopt DMA, No need to interrupt , Receive serial data with irregular length

describe :
When multiple data transmission through serial port ,CPU Multiple interrupts will be generated to receive serial data , This will greatly reduce CPU efficiency , At the same time, we need CPU To do something more important , How should we optimize ？
Like a four-axis aircraft , When continuously acquiring the attitude control direction , To receive serial port data .
answer : Use DMA, There is no need to CPU Interrupt can receive serial port data

1.DMA Introduce
DMA, Its full name is ： Direct Memory Access, Direct memory access , DMA There is no need for transmission CPU direct
Control transmission , Through hardware for RAM And I/O The device opens up a path for direct data transmission , Can make CPU Greatly improved the efficiency of .
2 stay main() Call the serial port configuration function , After initializing the serial port , Then enable UART1_RX Of DMA receive
2.1 stay main() Function , Use the following function to call the configuration function :

uart_init(115200);    // The serial port is initialized to 115200

2.2 uart_init() Function as follows :

void uart_init(u32 bound){
//GPIO Port settings 
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);    // Can make USART1,GPIOA The clock 
//USART1_TX GPIOA.9
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //PA.9
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;    // Multiplexing push pull output 
GPIO_Init(GPIOA, &GPIO_InitStructure);// initialization GPIOA.9

//USART1_RX    GPIOA.10 initialization 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;//PA10
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;// Floating input 
GPIO_Init(GPIOA, &GPIO_InitStructure);// initialization GPIOA.10 
USART_InitStructure.USART_BaudRate = bound;// Serial port baud rate 
USART_InitStructure.USART_WordLength = USART_WordLength_8b;// The word is 8 Bit data format 
USART_InitStructure.USART_StopBits = USART_StopBits_1;// A stop bit 
USART_InitStructure.USART_Parity = USART_Parity_No;// No parity bit 
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;// No hardware data flow control 
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;    // Transceiver mode 

USART_Init(USART1, &USART_InitStructure); // Initialize serial port 1
USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE); // Enable serial port 1 Of DMA send out 
}

 

 

3. stay main() Call in DMA Configuration function , Then initialize DMA1 Of UART1_RX After the passage , Then enable serial port 1 and DMA
3.1 As shown in the figure below ,UART1_RX be located DMA1 passageway 5:

So use variables in library functions DMA1_Channel5 To configure the UART1_RX.
3.2 stay main() Function , Define a receive array , Use the following 3 Parameters to call the configuration function :

u8 USART_RX_BUF[35]; // Receive buffer , Maximum USART_REC_LEN Bytes . The last byte is a newline character  
MYDMA_Config(DMA1_Channel5,(u32)&USART1->DR,(u32)USART_RX_BUF,35);//DMA1 passageway 5, Peripherals are serial ports 1, The memory is SendBuff, length 35,

3.3 MYDMA_Config() Function as follows , In the end, it will call MYDMA_Enable() Start once DMA transmission ！:

void MYDMA_Config(DMA_Channel_TypeDef* DMA_CHx,u32 cpar,u32 cmar,u16 cndtr)
{
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);    // Can make DMA transmission 
DMA_DeInit(DMA_CHx); // take DMA The passage of 1 Register reset to default 
DMA1_MEM_LEN=cndtr;
DMA_InitStructure.DMA_PeripheralBaseAddr = cpar; //DMA Peripheral base address 
DMA_InitStructure.DMA_MemoryBaseAddr = cmar; //DMA Memory base address 
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC; // Data transmission direction , Read from memory and send to peripheral 
DMA_InitStructure.DMA_BufferSize = cndtr; //DMA The tunnel DMA Cache size 
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; // The peripheral address register remains unchanged 
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; // The memory address register is incremented 
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; // Data width is 8 position 
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; // Data width is 8 position 
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; // Working in normal mode 
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //DMA passageway  x Have medium priority  
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable; //DMA passageway x Not set to memory to memory transfer 
DMA_Init(DMA_CHx, &DMA_InitStructure); // according to DMA_InitStruct The parameter specified in DMA The passage of USART1_Rx_DMA  Register identified 
USART_Cmd(USART1, ENABLE); // Enable serial port 1 
DMA_Cmd(DMA_CHx, ENABLE); // Can make USART1 TX DMA1  Indicated channel  
MYDMA_Enable(DMA1_Channel5);// Start once DMA transmission ！
} 

 

3.4 MYDMA_Enable() function

as follows :

void MYDMA_Enable(DMA_Channel_TypeDef*DMA_CHx)
{ 
DMA_Cmd(DMA_CHx, DISABLE ); // close USART1 TX DMA1  Indicated channel  
DMA_SetCurrDataCounter(DMA_CHx,DMA1_MEM_LEN);// Set the buffer size again , Pointing to the array 0
DMA_Cmd(DMA_CHx, ENABLE); // Can make USART1 TX DMA1  Indicated channel  
}  

4. Then when USART_RX_BUF[0] There are data , Appropriate delay 10ms, Give Way UCOS Continue to operate other processes , You can receive all the data of variable length
The code is as follows ( It can also be placed in a non operating system while in ):

 

if(USART_RX_BUF[0])    // Array 0 Have the data , explain DMA Start receiving a piece of data 
{
delay_ms(10); // Time delay 10ms, Give Way DMA While continuing to receive the following data , Can also run other processes  
printf("1:%s\r\n",USART_RX_BUF); // Print 
memset(USART_RX_BUF,0,35);    // Empty array 
MYDMA_Enable(DMA1_Channel5);// Start once DMA transmission ！
}

 

Delay in the above code 10ms, How much data can you accept ？

At baud rate 115200 Next ,1S Can accept 115200 position bit, Then a byte is 8 position bit, Plus a stop bit , So it's acceptable 12800 Data .

that 10ms, Acceptable 128 Data , If the data array is large , The delay time can be appropriately increased

5. The test results
As shown in the figure below , Echo as much as you enter , It shows that it has been successful , Here I set the receiving array size to 35, If you need longer data , Just change the size of the array

 

summary ：1 , Enable serial reception

            2, Enable serial port DMA

            3, Enabling channel

            4, Start transmitting