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15.DMA-I2C

DMA-I2C

DMA：I2C

DMA：I2CHardware connectionControl principleSoftware configurationPin definitionSoftware codeControl functionExperimental phenomenon

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


The tutorial only introduces the standard library project code

Hardware connection

Peripherals	Development board	Description
OLED: VCC	5V	OLED power supply
OLED: GND	GND	OLED common ground
OLED: SCL	PB8	Serial clock line (SCL)
OLED: SDA	PB9	Serial data line (SDA)

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

Main control chip	Pin	Main function (after reset)	Default multiplexing function	Redefine function
STM32F103RCT6	PB8	PB8	TIM4_CH3	I2C1_SCL/CAN_RX
STM32F103RCT6	PB9	PB9	TIM4_CH4	I2C1_SDA/CAN_TX

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


x
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   = OLE
 DMA-USART
Battery voltage detection (ADC)