DMA：I2C

The tutorial demonstrates I2C communication through DMA to control OLED display.

The tutorial only introduces the standard library project code

Hardware connection

Control principle

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I2C related knowledge will not be introduced, mainly DMA knowledge.

STM32F103RCT6 has two DMA controllers, DMA1 has 7 channels and DMA2 has 5 channels;

It is used for high-speed data transmission between peripherals and memory and between memory and memory.

DMA characteristics

DMA initialization and startup are completed by the CPU, and the transmission process is performed by the DMA controller without CPU participation, thus saving CPU resources for other operations.

DMA1 request for each channel

DMA2 request for each channel

This tutorial uses DMA1 channel 6.

Software configuration

Pin definition

Software code

Since the default function of the pin is the ordinary IO pin function, we need to use the redefine function.

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Product supporting data source code path: Attachment → Source code summary → 1.Base_Course → 15.I2C+DMA

Control function

The tutorial only briefly introduces the code, and you can open the project source code to read it in detail.

OLED_I2C_Init

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void OLED_I2C_Init(void)
{   
    GPIO_InitTypeDef GPIO_InitStructure;
    I2C_InitTypeDef I2C_InitStructure;

    RCC_APB1PeriphClockCmd(OLEDI2C_RCC, ENABLE);
    RCC_APB2PeriphClockCmd(OLED_RCC, ENABLE);

    //开启复用功能
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
    GPIO_PinRemapConfig(GPIO_Remap_I2C1, ENABLE);

    //PB8——SCL PB9——SDA
    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_OD;
    GPIO_InitStructure.GPIO_Pin   = OLED_SCL_Pin | OLED_SDA_Pin;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

    GPIO_Init(OLED_Port, &GPIO_InitStructure);

    I2C_DeInit(OLEDI2C);

    I2C1->CR1 |= 0x8000;  // 手动清除清BUSY
    I2C1->CR1 &= ~0x8000;

    I2C_InitStructure.I2C_Ack                 = I2C_Ack_Enable;
    I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
    I2C_InitStructure.I2C_ClockSpeed          = 400000;
    I2C_InitStructure.I2C_DutyCycle           = I2C_DutyCycle_2;
    I2C_InitStructure.I2C_Mode                = I2C_Mode_I2C;
    I2C_InitStructure.I2C_OwnAddress1         = 0x10; //此地址随便填，不做从机

    I2C_Init(OLEDI2C, &I2C_InitStructure);
    I2C_Cmd(OLEDI2C, ENABLE);

    MY_DMA_Transmit_InitConfig();//DMA初始化

    OLED_Init();//oled初始化

    OLED_Draw_Line("oled init success!", 1, true, true);
}

MY_DMA_Transmit_InitConfig

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void MY_DMA_Transmit_InitConfig(void)
{
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE); //Enable DMA transfer
    DMA_DeInit(DMA1_Channel6);

    DMA_InitTypeDef DMA_InitStructer;
    DMA_InitStructer.DMA_PeripheralBaseAddr = (uint32_t)&I2C1->DR; //Note that do not forget to add the & symbol when taking the address here
    DMA_InitStructer.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructer.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //The DR register position is fixed, there is only one, so the pointer cannot be moved after the transfer

    DMA_InitStructer.DMA_MemoryBaseAddr = (uint32_t)myData;
    DMA_InitStructer.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructer.DMA_MemoryInc = DMA_MemoryInc_Enable; // The pointer on the Data array needs to be incremented continuously so that the data can be sent out in turn, instead of just sending the first one in the array

    DMA_InitStructer.DMA_Mode = DMA_Mode_Normal; // DMA is set to normal mode
    DMA_InitStructer.DMA_DIR = DMA_DIR_PeripheralDST; // Send data to peripherals
    DMA_InitStructer.DMA_M2M = DMA_M2M_Disable; // Note that software triggering is not applicable

    DMA_InitStructer.DMA_BufferSize = 2;
    DMA_InitStructer.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_Init(DMA1_Channel6,&DMA_InitStructer);

    NVIC_InitTypeDef NVIC_InitStructure;
    //Interrupt priority NVIC settings
    NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel6_IRQn; //DMA interrupt
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; //Preempt priority level 0
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; //Sub priority level 1
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ channel is enabled
    NVIC_Init(&NVIC_InitStructure); //Initialize NVIC registers

    /* Enable DMA Channel6 complete transfer interrupt */
    DMA_ITConfig(DMA1_Channel6, DMA_IT_TC, ENABLE);
}

OLED_DMA_Transfer

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void OLED_DMA_Transfer(void)
{ 
    DMA_Cmd(DMA1_Channel6, DISABLE); //Disable the channel indicated by DMA
    DMA_SetCurrDataCounter(DMA1_Channel6, 2); //The size of the DMA buffer of the DMA channel
    DMA_Cmd(DMA1_Channel6, ENABLE); //Enable the channel indicated by DMA

    // I2C_DMACmd(OLEDI2C, ENABLE);
    // while(!DMA_GetFlagStatus(DMA1_FLAG_TC6));
}

Experimental phenomenon

The [I2C+DMA.hex] file generated by the project compilation is located in the OBJ folder of the [I2C+DMA] project. Find the [I2C+DMA.hex] file corresponding to the project and use the FlyMcu software to download the program to the development board.

After the program is successfully downloaded: OLED will display oled init success! and I2C + DMA Class! content.