I2C Communication(I2C)-OLED

The tutorial demonstrates the hardware I2C driving 0.91-inch OLED display to display content.

The tutorial only introduces the standard library project code

Hardware connection

Just install it to the corresponding interface:

Control principle

The I2C (Inter-Integrated Circuit) bus is a serial communication protocol consisting of a serial data line (SDA) and a serial clock line (SCL).

Serial Data Line (SDA): used to transmit data

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All devices use the same data line to communicate by transmitting data in binary form.

Serial Clock Line (SCL): used to synchronize data transmission

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The clock line generates pulses at a specific frequency to ensure that both the sending and receiving devices can transmit data at the same timing.

Multi-device communication: The I2C interface uses an address-based device identification mechanism to select a specific device to communicate with.

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Each I2C device has a unique address that identifies the device; the master device selects a specific device to communicate with by sending the device address

• I2C communication

IIC bus timing diagram

Idle state

SCL high level, SDA high level;

Start condition

SCL high level, SDA falling edge;

Stop condition

SCL high level, SDA rising edge;

Data transmission

SCL low level, SDA rising or falling edge;

Response signal

After receiving data from the device, it will send a low level to the master device to indicate successful reception;

Data validity

When the clock line is high, the data line must remain stable; when the clock line is low, the data line is allowed to change.

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SCL: high level → used for the start and end of communication
SCL: low level → used for data transmission and end

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 materials source code path: Attachment → Source code summary → 1.Base_Course → 10.I2C

Control function

The tutorial only briefly introduces the code, you can open the project source code to read the details.

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);

    // Enable the multiplexing function
    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);
    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;  // Fill in this address casually, do not do slave machine

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

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

OLED_Draw_String

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void OLED_Draw_String(char *data, uint8_t x, uint8_t y, bool clear, bool refresh)
{
    if (clear)
        OLED_Clear();
    SSD1306_GotoXY(x, y);
    SSD1306_Puts(data, &Font_7x10, SSD1306_COLOR_WHITE);
    if (refresh)
        OLED_Refresh();
}

OLED_Draw_Line

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void OLED_Draw_Line(char *data, uint8_t line, bool clear, bool refresh)
{
    if (line > 0 && line <= 3)
    {
        OLED_Draw_String(data, 0, 10 * (line - 1), clear, refresh);
    }
}

Experimental phenomenon

The I2c.hex file generated by the project compilation is located in the OBJ folder of the I2C project. Find the corresponding I2c.hex file of the project and use FlyMcu software to download the program into the development board.

After the program is downloaded successfully: OLED will display oled init success! And Hello wrold content.