S3c2440裸机-spi编程-3.gpio模拟spi驱动OLED

操作OLED，通过三条线(SCK、DO、CS)与OLED相连，这里没有DI是因为2440只会向OLED传数据而不用接收数据。

gpio_spi.c来实现gpio模拟spi，负责spi通讯。对于OLED，有专门的指令和数据格式，要传输的数据内容，在oled.c这一层来实现，负责组织数据。

因此，我们需要实现以上两个文件。

 

1.SPI初始化

新建一个gpio_spi.c文件，实现SPI初始化SPIInt()

 

1.1 GPIO init（pinmux管脚等配置）

上图J3为板子pin2pin到OLED的底座。

GPF1作为OLED片选引脚，设置为输出；
GPG4作为OLED的数据(Data)/命令(Command)选择引脚，设置为输出；
GPG5作为SPI的MISO，设置为输入（实际用不到）；
GPG6作为SPI的MOSI，设置为输出；
GPG7作为SPI的时钟CLK，设置为输出；

 

 

 根据gpio相关寄存器进行配置如下：用gpio配置成spi使用的各个引脚。

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void SPIInit(void){     /* 初始化引脚 */     SPI_GPIO_Init(); } static void SPI_GPIO_Init(void){     /* GPF1 as OLED_CSn output */     GPFCON &= ~(3<<(1*2));     GPFCON |= (1<<(1*2));     GPFDAT |= (1<<1);//取消OLED_CSn片选，pull up    /* GPG2 FLASH_CSn output     * GPG4 OLED_DC   output     * GPG5 SPIMISO   input     * GPG6 SPIMOSI   output     * GPG7 SPICLK    output     */     GPGCON &= ~((3<<(2*2)) | (3<<(4*2)) | (3<<(5*2)) | (3<<(6*2)) | (3<<(7*2)));     GPGCON |= ((1<<(2*2)) | (1<<(4*2)) | (1<<(6*2)) | (1<<(7*2)));     GPGDAT |= (1<<2);//取消FLASH_CSn 片选，pull up }

2.OLED初始化 

再新建一个oled.c文件，以实现初始化OLEDInit(),这里就对应power up sequence。

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void OLEDInit(void){     /* 向OLED发命令以初始化 */     OLEDWriteCmd(0xAE); /*display off*/     OLEDWriteCmd(0x00); /*set lower column address*/     OLEDWriteCmd(0x10); /*set higher column address*/     OLEDWriteCmd(0x40); /*set display start line*/     OLEDWriteCmd(0xB0); /*set page address*/     OLEDWriteCmd(0x81); /*contract control*/     OLEDWriteCmd(0x66); /*128*/     OLEDWriteCmd(0xA1); /*set segment remap*/     OLEDWriteCmd(0xA6); /*normal / reverse*/     OLEDWriteCmd(0xA8); /*multiplex ratio*/     OLEDWriteCmd(0x3F); /*duty = 1/64*/     OLEDWriteCmd(0xC8); /*Com scan direction*/     OLEDWriteCmd(0xD3); /*set display offset*/     OLEDWriteCmd(0x00);     OLEDWriteCmd(0xD5); /*set osc division*/     OLEDWriteCmd(0x80);     OLEDWriteCmd(0xD9); /*set pre-charge period*/     OLEDWriteCmd(0x1f);     OLEDWriteCmd(0xDA); /*set COM pins*/     OLEDWriteCmd(0x12);     OLEDWriteCmd(0xdb); /*set vcomh*/     OLEDWriteCmd(0x30);     OLEDWriteCmd(0x8d); /*set charge pump enable*/     OLEDWriteCmd(0x14); }

D/C即数据(Data)/命令(Command)选择引脚，它为高电平时，OLED即认为收到的是数据；它为低电平时，OLED即认为收到的是命令。先设置为命令模式，再片选OLED，再传输命令，再恢复成原来的模式和取消片选。

2.1 实现OLED写功能

写命令和写数据：

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static void OLEDWriteCmd(unsigned char cmd){     OLED_Set_DC(0); /* command */     OLED_Set_CS(0); /* select OLED */     SPISendByte(cmd);     OLED_Set_CS(1); /* de-select OLED */     OLED_Set_DC(1); /*  gpio output default is pull up*/ } static void OLEDWriteDat(unsigned char data){     OLED_Set_DC(1); /* data*/     OLED_Set_CS(0); /* select OLED */ SPISendByte(data); OLED_Set_CS(1); /* de-select OLED */ }

命令模式和片选就是单纯的gpio操作，非常简单如下：

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static void OLED_Set_DC(char val){     if (val)         GPGDAT |= (1<<4);     else         GPGDAT &= ~(1<<4); } static void OLED_Set_CS(char val){     if (val)         GPFDAT |= (1<<1);     else         GPFDAT &= ~(1<<1); }

2.2 SPISendByte()

还剩下SPISendByte()函数，它属于SPI协议，放在gpio_spi.c里面：

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void SPISendByte(unsigned char val){     int i;     for (i = 0; i < 8; i++){         SPI_Set_CLK(0);         SPI_Set_DO(val & 0x80);//MSB         SPI_Set_CLK(1);         val <<= 1;     } } static void SPI_Set_CLK(char val){     if (val)         GPGDAT |= (1<<7);     else         GPGDAT &= ~(1<<7); } static void SPI_Set_DO(char val){     if (val)         GPGDAT |= (1<<6);     else         GPGDAT &= ~(1<<6); }

发送数据要满足SPI的时序要求，参考前面的介绍：

 

SPISendByte是把一个byte数据从高位往低位依次发送到DO。spi配置模式0， 主控先设置CLK为低，由于是MSB, 先传送高位，然后CLK为高，在CLK这个上升沿,DO的数据被锁存，OLED就读取了一位数据。接着左移一位，传输下一位。通过SPI_Set_CLK()和SPI_Set_DO()配置SCK和DO的时序，用gpio模拟出了spi。至此，SPI初始化和OLED初始化就基本完成了，接下来就是OLED显示部分。

这里gpio模拟spi传送时主控没有加延时控制SCK的频率，那是由于jz2440本身cpu运行就很慢，这里不延时也是能满足该款外设的spi传输时序，如果cpu很快，那么需要控制spi时序。

3.驱动显示OLED

如何在OLED上显示一个字符？根据前面一节OLED面板的显示原理。代码实现如下：

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static void OLEDSetPos(int page, int col){     OLEDWriteCmd(0xB0 + page); /* page address */     OLEDWriteCmd(col & 0xf);   /* Lower Column Start Address */     OLEDWriteCmd(0x10 + (col >> 4));   /* Lower Higher Start Address */ } /* page: 0-7  * col : 0-127  * 字符: 8x16象素  */ void OLEDPutChar(int page, int col, char c){     int i = 0;     /* 得到字模 */     const unsigned char *dots = oled_asc2_8x16[c - ' '];     /* 发给OLED */     OLEDSetPos(page, col);     /* 发出8字节数据 */     for (i = 0; i < 8; i++)         OLEDWriteDat(dots[i]);     OLEDSetPos(page+1, col);     /* 发出8字节数据 */     for (i = 0; i < 8; i++)         OLEDWriteDat(dots[i+8]); } /* page: 0-7  * col : 0-127  * 字符: 8x16象素  */ void OLEDPrint(int page, int col, char *str){     int i = 0;     while (str[i]){         OLEDPutChar(page, col, str[i]);         col += 8;         if (col > 127) {             col = 0;             page += 2;         }         i++;     } } static void OLEDSetPos(int page, int col){     OLEDWriteCmd(0xB0 + page); /* page address */     OLEDWriteCmd(col & 0xf);   /* Lower Column Start Address */     OLEDWriteCmd(0x10 + (col >> 4));   /* Lower Higher Start Address */ } static void OLEDClear(void){     int page, i;     for (page = 0; page < 8; page ++){         OLEDSetPos(page, 0);         for (i = 0; i < 128; i++)             OLEDWriteDat(0);     } }

 完整代码如下：

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/************************** gpio_spi.c ****************/ #include "s3c24xx.h" /* 用GPIO模拟SPI */ static void SPI_GPIO_Init(void) {     /* GPF1 OLED_CSn output */     GPFCON &= ~(3<<(1*2));     GPFCON |= (1<<(1*2));     GPFDAT |= (1<<1);       /* GPG2 FLASH_CSn output     * GPG4 OLED_DC   output     * GPG5 SPIMISO   input     * GPG6 SPIMOSI   output     * GPG7 SPICLK    output     */     GPGCON &= ~((3<<(2*2)) | (3<<(4*2)) | (3<<(5*2)) | (3<<(6*2)) | (3<<(7*2)));     GPGCON |= ((1<<(2*2)) | (1<<(4*2)) | (1<<(6*2)) | (1<<(7*2)));     GPGDAT |= (1<<2); }   static void SPI_Set_CLK(char val) {     if (val)         GPGDAT |= (1<<7);     else         GPGDAT &= ~(1<<7); }   static void SPI_Set_DO(char val) {     if (val)         GPGDAT |= (1<<6);     else         GPGDAT &= ~(1<<6); }   void SPISendByte(unsigned char val) {     int i;     for (i = 0; i < 8; i++)     {         SPI_Set_CLK(0);         SPI_Set_DO(val & 0x80);         SPI_Set_CLK(1);         val <<= 1;     }       }   void SPIInit(void) {     /* 初始化引脚 */     SPI_GPIO_Init(); }   /******************* oled.c****************/ #include "oledfont.h" #include "gpio_spi.h" #include "s3c24xx.h" static void OLED_Set_DC(char val) {     if (val)         GPGDAT |= (1<<4);     else         GPGDAT &= ~(1<<4); } static void OLED_Set_CS(char val) {     if (val)         GPFDAT |= (1<<1);     else         GPFDAT &= ~(1<<1); } static void OLEDWriteCmd(unsigned char cmd) {     OLED_Set_DC(0); /* command */     OLED_Set_CS(0); /* select OLED */       SPISendByte(cmd);       OLED_Set_CS(1); /* de-select OLED */     OLED_Set_DC(1); /*  */ } static void OLEDWriteDat(unsigned char dat) {     OLED_Set_DC(1); /* data */     OLED_Set_CS(0); /* select OLED */       SPISendByte(dat);       OLED_Set_CS(1); /* de-select OLED */     OLED_Set_DC(1); /*  */ } static void OLEDSetPageAddrMode(void) {     OLEDWriteCmd(0x20);     OLEDWriteCmd(0x02); } static void OLEDSetPos(int page, int col) {     OLEDWriteCmd(0xB0 + page); /* page address */       OLEDWriteCmd(col & 0xf);   /* Lower Column Start Address */     OLEDWriteCmd(0x10 + (col >> 4));   /* Lower Higher Start Address */ } static void OLEDClear(void) {     int page, i;     for (page = 0; page < 8; page ++)     {         OLEDSetPos(page, 0);         for (i = 0; i < 128; i++)             OLEDWriteDat(0);     } } void OLEDInit(void) {     /* 向OLED发命令以初始化 */     OLEDWriteCmd(0xAE); /*display off*/     OLEDWriteCmd(0x00); /*set lower column address*/     OLEDWriteCmd(0x10); /*set higher column address*/     OLEDWriteCmd(0x40); /*set display start line*/     OLEDWriteCmd(0xB0); /*set page address*/     OLEDWriteCmd(0x81); /*contract control*/     OLEDWriteCmd(0x66); /*128*/     OLEDWriteCmd(0xA1); /*set segment remap*/     OLEDWriteCmd(0xA6); /*normal / reverse*/     OLEDWriteCmd(0xA8); /*multiplex ratio*/     OLEDWriteCmd(0x3F); /*duty = 1/64*/     OLEDWriteCmd(0xC8); /*Com scan direction*/     OLEDWriteCmd(0xD3); /*set display offset*/     OLEDWriteCmd(0x00);     OLEDWriteCmd(0xD5); /*set osc division*/     OLEDWriteCmd(0x80);     OLEDWriteCmd(0xD9); /*set pre-charge period*/     OLEDWriteCmd(0x1f);     OLEDWriteCmd(0xDA); /*set COM pins*/     OLEDWriteCmd(0x12);     OLEDWriteCmd(0xdb); /*set vcomh*/     OLEDWriteCmd(0x30);     OLEDWriteCmd(0x8d); /*set charge pump enable*/     OLEDWriteCmd(0x14);       OLEDSetPageAddrMode();       OLEDClear();           OLEDWriteCmd(0xAF); /*display ON*/    }   /* page: 0-7  * col : 0-127  * 字符: 8x16象素  */ void OLEDPutChar(int page, int col, char c) {     int i = 0;     /* 得到字模 */     const unsigned char *dots = oled_asc2_8x16[c - ' '];       /* 发给OLED */     OLEDSetPos(page, col);     /* 发出8字节数据 */     for (i = 0; i < 8; i++)         OLEDWriteDat(dots[i]);       OLEDSetPos(page+1, col);     /* 发出8字节数据 */     for (i = 0; i < 8; i++)         OLEDWriteDat(dots[i+8]);   }   /* page: 0-7  * col : 0-127  * 字符: 8x16象素  */ void OLEDPrint(int page, int col, char *str) {     int i = 0;     while (str[i])     {         OLEDPutChar(page, col, str[i]);         col += 8;         if (col > 127)         {             col = 0;             page += 2;         }         i++;     } }