[N32L43X Review] 2. Simulating I2C to drive OLED

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[N32L43X Review] 2. Simulating I2C to drive OLED [Copy link]

The I2C bus is a serial bus that we often use in our development process.

The main features of I2C include:

1. Only two buses are needed;

2. There is a simple master/slave relationship between all components, and each device connected to the bus can be software-addressed by a unique address;

3. It is a true multi-master bus that can provide arbitration and conflict detection;

4. Maximum number of slaves: theoretically 127;

5. Transmission speed:

Standard Mode: Standard Mode = 100 Kbps

Fast Mode: Fast Mode = 400 Kbps

High speed mode: High speed mode = 3.4 Mbps

Ultra fast mode: Ultra fast mode = 5 Mbps

For detailed explanation of I2C bus protocol, please refer to the following materials:

UM10204_I2C-bus specification and user manual-Rev.7.0.pdf (733.36 KB, downloads: 1)

I2C总线规范.pdf (918.13 KB, downloads: 2)

This article mainly introduces GPIO software simulation to realize I2C to drive 0.96-inch OLED display. OLED display information: 0.96寸OLED使用文档V3.0.pdf (1.68 MB, downloads: 2)

Hardware Hookup

GND —— GND

VCC —— 3.3V

SCL —— PB8

SDA —— PB9

Software Code

I2C Code:

//设置SDA输入模式
void SDA_IN(void)
{
    GPIO_InitType GPIO_InitStructure;

    RCC_EnableAPB2PeriphClk( SDA_GPIO_CRM_CLK, ENABLE);

    GPIO_InitStruct(&GPIO_InitStructure);
    GPIO_InitStructure.Pin = SDA_PIN;
    GPIO_InitStructure.GPIO_Slew_Rate = GPIO_Slew_Rate_High;
    GPIO_InitStructure.GPIO_Current = GPIO_DC_4mA;
    GPIO_InitStructure.GPIO_Pull = GPIO_Pull_Up;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Input;
    GPIO_InitPeripheral(SDA_GPIO, &GPIO_InitStructure);
}

//设置SDA为输出模式
void SDA_OUT(void)
{
    GPIO_InitType GPIO_InitStructure;

    RCC_EnableAPB2PeriphClk( SDA_GPIO_CRM_CLK, ENABLE);

    GPIO_InitStruct(&GPIO_InitStructure);
    GPIO_InitStructure.Pin = SDA_PIN;
    GPIO_InitStructure.GPIO_Slew_Rate = GPIO_Slew_Rate_High;
    GPIO_InitStructure.GPIO_Current = GPIO_DC_4mA;
    GPIO_InitStructure.GPIO_Pull = GPIO_Pull_Up;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitPeripheral(SDA_GPIO, &GPIO_InitStructure);
}

//设置SCL电平
void I2C_SCL(int n)
{
    if(n == 1)
    {
        GPIO_WriteBit(SCL_GPIO, SCL_PIN, Bit_SET); //设置SCL为高电平
    }
    else
    {
        GPIO_WriteBit(SCL_GPIO, SCL_PIN, Bit_RESET); //设置SCL为低电平
    }
}

//设置SDA电平
void I2C_SDA(int n)
{
    if(n == 1)
    {
        GPIO_WriteBit(SDA_GPIO, SDA_PIN, Bit_SET); //设置SDA为高电平
    }
    else
    {
        GPIO_WriteBit(SDA_GPIO, SDA_PIN, Bit_RESET); //设置SDA为低电平
    }
}

//读取SDA电平
unsigned char READ_SDA(void)
{
    return GPIO_ReadInputDataBit(SDA_GPIO, SDA_PIN); //读取SDA电平
}

//I2C初始化
void I2C_Initial(void)
{
    GPIO_InitType GPIO_InitStructure;

    //根据GPIO组初始化GPIO时钟
    RCC_EnableAPB2PeriphClk( SCL_GPIO_CRM_CLK, ENABLE);
    RCC_EnableAPB2PeriphClk( SDA_GPIO_CRM_CLK, ENABLE);

    //GPIO_SCL初始化设置
    GPIO_InitStruct(&GPIO_InitStructure);
    GPIO_InitStructure.Pin = SCL_PIN;
    GPIO_InitStructure.GPIO_Slew_Rate = GPIO_Slew_Rate_High;
    GPIO_InitStructure.GPIO_Current = GPIO_DC_4mA;
    GPIO_InitStructure.GPIO_Pull = GPIO_Pull_Up;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitPeripheral(SCL_GPIO, &GPIO_InitStructure);

    //GPIO_SDA初始化设置
    GPIO_InitStruct(&GPIO_InitStructure);
    GPIO_InitStructure.Pin = SDA_PIN;
    GPIO_InitStructure.GPIO_Slew_Rate = GPIO_Slew_Rate_High;
    GPIO_InitStructure.GPIO_Current = GPIO_DC_4mA;
    GPIO_InitStructure.GPIO_Pull = GPIO_Pull_Up;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitPeripheral(SDA_GPIO, &GPIO_InitStructure);
    //SCL、SDA的初始化均为高电平
    I2C_SCL(1);
    I2C_SDA(1);
}

//I2C Start
void I2C_Start(void)
{
    SDA_OUT();
    I2C_SDA(1);
    I2C_SCL(1);
    Delay_Us(4);
    I2C_SDA(0); //START:when CLK is high,DATA change form high to low
    Delay_Us(4);
    I2C_SCL(0); //钳住I2C总线,准备发送或接收数据
}

//I2C Stop
void I2C_Stop(void)
{
    SDA_OUT();
    I2C_SCL(0);
    I2C_SDA(0); //STOP:when CLK is high DATA change form low to high
    Delay_Us(4);
    I2C_SCL(1);
    I2C_SDA(1); //发送I2C总线结束信号
    Delay_Us(4);
}

//I2C_Wait_ack 返回HAL_OK表示wait成功,返回HAL_ERROR表示wait失败
unsigned char I2C_Wait_Ack(void) //IIC_Wait_ack,返回wait失败或是成功
{
    unsigned char ucErrTime = 0;

    SDA_IN();
    I2C_SDA(1);
    Delay_Us(1);
    I2C_SCL(1);
    Delay_Us(1);

    while(READ_SDA())
    {
        ucErrTime++;

        if(ucErrTime > 250)
        {
            I2C_Stop();
            return HAL_ERROR;
        }
    }

    I2C_SCL(0);
    return HAL_OK;
}

//产生ACK应答
void I2C_Ack(void)
{
    I2C_SCL(0);
    SDA_OUT();
    I2C_SDA(0);
    Delay_Us(2);
    I2C_SCL(1);
    Delay_Us(2);
    I2C_SCL(0);
}

//产生NACK应答
void I2C_NAck(void)
{
    I2C_SCL(0);
    SDA_OUT();
    I2C_SDA(1);
    Delay_Us(2);
    I2C_SCL(1);
    Delay_Us(2);
    I2C_SCL(0);
}

//I2C_Send_Byte,入口参数为要发送的字节
void I2C_Send_Byte(unsigned char txd)
{
    unsigned char cnt = 0;

    SDA_OUT();
    I2C_SCL(0);

    for(cnt = 0; cnt < 8; cnt++)
    {
        I2C_SDA((txd & 0x80) >> 7);
        txd <<= 1;
        Delay_Us(2);
        I2C_SCL(1);
        Delay_Us(2);
        I2C_SCL(0);
        Delay_Us(2);
    }
}

//I2C_Read_Byte,入口参数为是否要发送ACK信号
unsigned char I2C_Read_Byte(unsigned char ack)
{
    unsigned char cnt, rec = 0;

    SDA_IN();

    for(cnt = 0; cnt < 8; cnt++)
    {
        I2C_SCL(0);
        Delay_Us(2);
        I2C_SCL(1);
        rec <<= 1;

        if(READ_SDA())
        {
            rec++;
        }

        Delay_Us(1);
    }

    if(!ack)
    {
        I2C_NAck();
    }
    else
    {
        I2C_Ack();
    }

    return rec;
}

OLED Code:

//向设备写控制命令
static void OLED_Write_CMD(unsigned char cmd)
{
    I2C_Start();
    I2C_Send_Byte(0x78);
    I2C_Wait_Ack();
    I2C_Send_Byte(0x00);
    I2C_Wait_Ack();
    I2C_Send_Byte(cmd);
    I2C_Wait_Ack();
    I2C_Stop();
}

//向设备写数据
static void OLED_Write_Date(unsigned char date)
{
    I2C_Start();
    I2C_Send_Byte(0x78);
    I2C_Wait_Ack();
    I2C_Send_Byte(0x40);
    I2C_Wait_Ack();
    I2C_Send_Byte(date);
    I2C_Wait_Ack();
    I2C_Stop();
}

//坐标设置
static void OLED_Set_Pos(unsigned char x, unsigned char y)
{
    OLED_Write_CMD(0xB0 + y);
    OLED_Write_CMD(((x & 0xF0) >> 4) | 0x10);
    OLED_Write_CMD(x & 0x0F);
}

//开启OLED显示
static void OLED_Display_On(void)
{
    OLED_Write_CMD(0x8D); //SET DCDC命令
    OLED_Write_CMD(0x14); //DCDC ON
    OLED_Write_CMD(0xAF); //DISPLAY ON
}

//关闭OLED显示
static void OLED_Display_Off(void)
{
    OLED_Write_CMD(0x8D); //SET DCDC命令
    OLED_Write_CMD(0x10); //DCDC OFF
    OLED_Write_CMD(0xAE); //DISPLAY OFF
}

//OLED清屏
void OLED_Clear(void)
{
    unsigned char cnt, count;

    for(cnt = 0; cnt < 8; cnt++)
    {
        OLED_Write_CMD(0xB0 + cnt);
        OLED_Write_CMD(0x00);
        OLED_Write_CMD(0x10);

        for(count = 0; count < 128; count++)
        {
            OLED_Write_Date(0x00);
        }
    }
}

//OLED清行
void OLED_Clear_Row(unsigned char n)
{
    unsigned char count;

    OLED_Write_CMD(0xB0 + n);
    OLED_Write_CMD(0x00);
    OLED_Write_CMD(0x10);

    for(count = 0; count < 128; count++)
    {
        OLED_Write_Date(0x00);
    }
}

//OLED填满屏幕
void OLED_Fill(void)
{
    unsigned char cnt, count;

    for(cnt = 0; cnt < 8; cnt++)
    {
        OLED_Write_CMD(0xB0 + cnt); //设置页地址（0~7）
        OLED_Write_CMD(0x00); //设置显示位置—列低地址
        OLED_Write_CMD(0x10); //设置显示位置—列高地址

        for(count = 0; count < 128; count++)
        {
            OLED_Write_Date(0x01);
        }
    }
}

//指定位置显示一个字符
//x:0~127
//y:0~63
//chr:字符
//size:选择字体 16/12
void OLED_ShowChar(unsigned char x, unsigned char y, unsigned char chr, unsigned char size)
{
    unsigned char offset = 0, cnt = 0;

    offset = chr - ' '; //计算偏移量

    if(x > 128 - 1)
    {
        x = 0;
        y = y + 2;
    }

    if(size == 16)
    {
        OLED_Set_Pos(x, y);

        for(cnt = 0; cnt < 8; cnt++)
        {
            OLED_Write_Date(F8x16[offset * 16 + cnt]);
        }

        OLED_Set_Pos(x, y + 1);

        for(cnt = 0; cnt < 8; cnt++)
        {
            OLED_Write_Date(F8x16[offset * 16 + cnt + 8]);
        }
    }
    else
    {
        OLED_Set_Pos(x, y);

        for(cnt = 0; cnt < 6; cnt++)
        {
            OLED_Write_Date(F6x8[offset][cnt]);
        }
    }
}

unsigned int oled_pow(unsigned char m, unsigned char n)
{
    unsigned int result = 1;

    while(n--)
    {
        result *= m;
    }

    return result;
}

//指定位置显示一个数字
//x,y:起点坐标
//num:数值(0~4294967295)
//len:数字的位数
//size:字体大小
void OLED_ShowNum(unsigned char x, unsigned char y, unsigned int num, unsigned char len, unsigned char size)
{
    unsigned char cnt, temp;
    unsigned char show = 0;

    for(cnt = 0; cnt < len; cnt++)
    {
        temp = (num / oled_pow(10, len - cnt - 1)) % 10;

        if(show == 0 && cnt < (len - 1))
        {
            if(temp == 0)
            {
                OLED_ShowChar(x + (size / 2) * cnt, y, ' ', size);
                continue;
            }
            else
            {
                show = 1;
            }
        }

        OLED_ShowChar(x + (size / 2) * cnt, y, temp + '0', size);
    }
}

//指定位置显示字符串
void OLED_ShowString(unsigned char x, unsigned char y, unsigned char *chr, unsigned char size)
{
    unsigned char cnt = 0;

    while(chr[cnt] != '\0')
    {
        OLED_ShowChar(x, y, chr[cnt], size);
        x += 8;

        if(x > 120)
        {
            x = 0;
            y += 2;
        }

        cnt++;
    }
}

//显示汉字
void OLED_ShowCHinese(unsigned char x, unsigned char y, unsigned char no)
{
    unsigned char cnt, addr = 0;

    OLED_Set_Pos(x, y);

    for(cnt = 0; cnt < 16; cnt++)
    {
        OLED_Write_Date(Hzk[2 * no][cnt]);
        addr++;
    }

    OLED_Set_Pos(x, y + 1);

    for(cnt = 0; cnt < 16; cnt++)
    {
        OLED_Write_Date(Hzk[2 * no + 1][cnt]);
        addr++;
    }
}

//显示图片
/*
	[url=home.php?mod=space&uid=159083]@brief[/url] 显示图片
	@param			x0：起始列地址
					y0：起始页地址
					x1：终止列地址
					y1：终止页地址
					BMP[]：存放图片代码的数组
	@retval			无
 */
void OLED_DrawBMP(unsigned char x0, unsigned char y0, unsigned char x1, unsigned char y1, const unsigned char BMP[])
{
    unsigned int j = 0; //定义变量
    unsigned char x, y; //定义变量

    if(y1 % 8 == 0)
    {
        y = y1 / 8; //判断终止页是否为8的整数倍
    }
    else
    {
        y = y1 / 8 + 1;
    }

    for(y = y0; y < y1; y++) //从起始页开始，画到终止页
    {
        OLED_Set_Pos(x0, y); //在页的起始列开始画

        for(x = x0; x < x1; x++) //画x1 - x0 列
        {
            OLED_Write_Date(BMP[j++]); //画图片的点
        }
    }
}

//显示动图
/*
	@brief			显示动图
	@param			x0：起始列地址
				y0：起始页地址
				x1：终止列地址
				y1：终止页地址
				k: 帧个数
				m: 单帧数组大小
				BMP[][m]：存放动图代码的数组
	@retval			无
 */
void OLED_DrawGIF(unsigned char x0, unsigned char y0, unsigned char x1, unsigned char y1, unsigned char k, int m, const unsigned char GIF[][m])
{
    unsigned int j = 0; //定义变量
    unsigned char x, y, i; //定义变量

    if(y1 % 8 == 0)
    {
        y = y1 / 8; //判断终止页是否为8的整数倍
    }
    else
    {
        y = y1 / 8 + 1;
    }

    for (i = 0; i < k; i++) //从第一帧开始画
    {
        j = 0;

        for(y = y0; y < y1; y++) //从起始页开始，画到终止页
        {
            OLED_Set_Pos(x0, y); //在页的起始列开始画

            for(x = x0; x < x1; x++) //画x1 - x0 列
            {
                OLED_Write_Date(GIF[i][j++]); //画图片的点
            }
        }

        //Delay_Ms(80);
    }
}

//OLED初始化
void OLED_Init(void)
{
    I2C_Initial();
    Delay_Ms(200);
    OLED_Write_CMD(0xAE); //display off
    OLED_Write_CMD(0x00); //set low column address
    OLED_Write_CMD(0x10); //set high column address
    OLED_Write_CMD(0x40); //set start line address
    OLED_Write_CMD(0xB0); //set page address
    OLED_Write_CMD(0x81); //contract control
    OLED_Write_CMD(0xFF); //128
    OLED_Write_CMD(0xA1); //set segment remap
    OLED_Write_CMD(0xA6); //normal / reverse
    OLED_Write_CMD(0xA8); //set multiplex ratio(1 to 64)
    OLED_Write_CMD(0x3F); //1/32 duty
    OLED_Write_CMD(0xC8); //Com scan direction
    OLED_Write_CMD(0xD3); //set display offset
    OLED_Write_CMD(0x00); //
    OLED_Write_CMD(0xD5); //set osc division
    OLED_Write_CMD(0x80); //
    OLED_Write_CMD(0xD8); //set area color mode off
    OLED_Write_CMD(0x05); //
    OLED_Write_CMD(0xD9); //Set Pre-Charge Period
    OLED_Write_CMD(0xF1); //
    OLED_Write_CMD(0xDA); //set com pin configuartion
    OLED_Write_CMD(0x12); //
    OLED_Write_CMD(0xDB); //set Vcomh
    OLED_Write_CMD(0x30); //
    OLED_Write_CMD(0x8D); //set charge pump enable
    OLED_Write_CMD(0x14); //
    OLED_Write_CMD(0xAF); //turn on oled panel
}

Running Tests

SW_I2C_OLED

Test code
N32L43x_SW_I2C_OLED.zip (516.95 KB, downloads: 30)

freebsder

Thanks for sharing, looking forward to the follow-up.

lugl4313820

In fact, its hardware I2C speed will be much higher, so the refresh rate will be much better. You can try it when you get a chance.

805721366

lugl4313820 posted on 2022-8-14 22:07 In fact, its hardware I2C speed will be much higher, so the refresh rate will be much better. I will try it if I have a chance.

Hardware I2C is indeed fast, I have tested it https://en.eeworld.com/bbs/thread-1212208-1-1.html#pid3164870

[N32L43X Review] 2. Simulating I2C to drive OLED [Copy link]

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