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。
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。
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:
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:
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:
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:
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:
/************************** 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++; } }