树莓派 -- oled 续（1） wiringPi

在上文中，分析了wiringPi 的oled demo是使用devfs来控制spi master和spi slave通讯。
https://blog.youkuaiyun.com/feiwatson/article/details/81149028

再详细分析一下demo的OLED SSD1306相关代码。

定义一个buffer

unsigned char buffer[1024];

初始化

void SSD1306_begin()
{
    pinMode(RST,OUTPUT); //Pin24 设置为输出
    pinMode(DC,OUTPUT);  //Pin27 设置为输出
    wiringPiSPISetup(channel,2000000);    //2M

    digitalWrite(RST,HIGH);   //reset
    delay(10);
    digitalWrite(RST,LOW);
    delay(10);
    digitalWrite(RST,HIGH);

    command(SSD1306_DISPLAYOFF);
    command(SSD1306_SETDISPLAYCLOCKDIV);
    command(0x80);                              // the suggested ratio 0x80

    command(SSD1306_SETMULTIPLEX);
    command(0x3F);
    command(SSD1306_SETDISPLAYOFFSET);
    command(0x0);                               // no offset
    command(SSD1306_SETSTARTLINE | 0x0);        // line #0
    command(SSD1306_CHARGEPUMP);
    command((vccstate == SSD1306_EXTERNALVCC) ? 0x10 : 0x14);

    command(SSD1306_MEMORYMODE);
    command(0x00);                              // 0x0 act like ks0108

    command(SSD1306_SEGREMAP | 0x1);
    command(SSD1306_COMSCANDEC);
    command(SSD1306_SETCOMPINS);
    command(0x12);           // TODO - calculate based on _rawHieght ?
    command(SSD1306_SETCONTRAST);
    command((vccstate == SSD1306_EXTERNALVCC) ? 0x9F : 0xCF);
    command(SSD1306_SETPRECHARGE);
    command((vccstate == SSD1306_EXTERNALVCC) ? 0x22 : 0xF1);
    command(SSD1306_SETVCOMDETECT);
    command(0x40);
    command(SSD1306_DISPLAYALLON_RESUME);
    command(SSD1306_NORMALDISPLAY);
    command(SSD1306_DISPLAYON);
}

设置一个pixel对应的buffer中的bit. 一列8个pixel对应一个buffer字节

void SSD1306_pixel(int x,int y,char color)
{
    if(x > width || y > height)return ;
    if(color)
        buffer[x+(y/8)*width] |= 1<<(y%8);
    else
        buffer[x+(y/8)*width] &= ~(1<<(y%8));
}

其他的SSD1306_bitmap , SSD1306_string, SSD1306_char3216, SSD1306_char1616等函数通过调用SSD1306_pixel设置buffer

将buffer中缓冲的图像显示

void SSD1306_display()
{
    command(SSD1306_COLUMNADDR);
    command(0);         //cloumn start address
    command(width -1); //cloumn end address
    command(SSD1306_PAGEADDR);
    command(0);         //page atart address
    command(pages -1); //page end address
    digitalWrite(DC,HIGH);
    wiringPiSPIDataRW(channel,buffer,sizeof(buffer));
}

图片中显示图像的代码如下

int main(int argc,char **argv)
{
    time_t now;
    struct tm *timenow;
    if(wiringPiSetup() < 0)return 1;
    printf("OLED Test Program !!!\n");

    SSD1306_begin();
    SSD1306_bitmap(0,0,waveshare,128,64);
    SSD1306_display();
    delay(2000);
    SSD1306_clear();
    while(1)
    {
        time(&now);
        timenow = localtime(&now);

        SSD1306_bitmap(0, 2, Singal816, 16, 8); 
        SSD1306_bitmap(24, 2,Bluetooth88, 8, 8); 
        SSD1306_bitmap(40, 2, Msg816, 16, 8); 
        SSD1306_bitmap(64, 2, GPRS88, 8, 8); 
        SSD1306_bitmap(90, 2, Alarm88, 8, 8); 
        SSD1306_bitmap(112, 2, Bat816, 16, 8); 

        SSD1306_string(0, 52, "MUSIC", 12, 0); 
        SSD1306_string(52, 52, "MENU", 12, 0); 
        SSD1306_string(98, 52, "PHONE", 12, 0);

        SSD1306_char3216(0,16, value[timenow->tm_hour/10]);
        SSD1306_char3216(16,16, value[timenow->tm_hour%10]);
        SSD1306_char3216(32,16, ':');
        SSD1306_char3216(48,16, value[timenow->tm_min/10]);
        SSD1306_char3216(64,16, value[timenow->tm_min%10]);
        SSD1306_char3216(80,16, ':');
        SSD1306_char3216(96,16, value[timenow->tm_sec/10]);
        SSD1306_char3216(112,16, value[timenow->tm_sec%10]);

        SSD1306_display();
    }
    return 0;
}