【摘要】 OLED顯示屏在是智能手環(huán)，智能手表上用的非常的多，功耗低，不刺眼，優(yōu)點(diǎn)特別多。本篇文章就介紹,在Linux系統(tǒng)里如何使用OLED顯示屏，要使用OLED顯示屏，大致分為兩步: (1) 針對(duì)OLED顯示屏編寫(xiě)一個(gè)驅(qū)動(dòng) (2) 編寫(xiě)應(yīng)用層程序進(jìn)行測(cè)試。

1. 前言

OLED顯示屏在是智能手環(huán)，智能手表上用的非常的多，功耗低，不刺眼，優(yōu)點(diǎn)特別多。本篇文章就介紹,在Linux系統(tǒng)里如何使用OLED顯示屏，要使用OLED顯示屏，大致分為兩步: (1) 針對(duì)OLED顯示屏編寫(xiě)一個(gè)驅(qū)動(dòng) (2) 編寫(xiě)應(yīng)用層程序進(jìn)行測(cè)試。

采用的OLED顯示屏是0.96寸SPI接口顯示屏，分辨率是128*64，比較便宜，淘寶上非常多。

測(cè)試開(kāi)發(fā)板采用友善之臂Tiny4412，三星的EXYNOS-4412芯片，4核1.5GHZ，板載8G-EMMC，2G-DDR。

2. 硬件接線效果

3. 驅(qū)動(dòng)代碼

Linux內(nèi)核提供了標(biāo)準(zhǔn)SPI子系統(tǒng)框架，和前面介紹的IIC子系統(tǒng)框架使用類(lèi)似，代碼分為設(shè)備端和驅(qū)動(dòng)端，Linux內(nèi)核提供子系統(tǒng)的目的就是為了統(tǒng)一驅(qū)動(dòng)編寫(xiě)標(biāo)準(zhǔn)，提高驅(qū)動(dòng)代碼的移植性。

本篇文章代碼沒(méi)有采用SPI子系統(tǒng)框架，采用單片機(jī)慣用的模擬SPI時(shí)序，對(duì)入門(mén)而言，代碼更容易理解。

3.1 oled.c 驅(qū)動(dòng)示例代碼

#include 
#include 
#include  
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

/*
定義OLED需要使用的寄存器
*/
static volatile unsigned int *GPB_CON=NULL;
static volatile unsigned int *GPB_DAT=NULL;

//OLED屏幕底層接口
#define OLED_SCK(x) if(x){*GPB_DAT|=1<<0;}else{*GPB_DAT&=~(1<<0);}
#define OLED_MOSI(x) if(x){*GPB_DAT|=1<<3;}else{*GPB_DAT&=~(1<<3);}
#define OLED_RES(x)  if(x){*GPB_DAT|=1<<4;}else{*GPB_DAT&=~(1<<4);}
#define OLED_DC(x)   if(x){*GPB_DAT|=1<<5;}else{*GPB_DAT&=~(1<<5);}
#define OLED_CS(x)   if(x){*GPB_DAT|=1<<1;}else{*GPB_DAT&=~(1<<1);}

//命令與數(shù)據(jù)區(qū)分
#define OLED_CMD 0
#define OLED_DAT 1

//函數(shù)聲明區(qū)域
static void OLED_WriteOneByte(u8 data,u8 cmd);
static u8 OLED_GPIO_Init(void);
static void OLED_Init(void);
static void OLED_Clear(u8 data);
static void OLED_DrawPoint(u8 x,u8 y,u8 c);
static void OLED_RefreshGRAM(void);
/*
函數(shù)功能: OLED對(duì)應(yīng)的GPIO口初始化
硬件連接:
OLED模塊---Tiny4412開(kāi)發(fā)板
GND--------GND
VCC--------VCC(5V)
D0---------SCL--------------GPB_0
D1---------MOSI-------------GPB_3
RES--------復(fù)位-------------GPB_4
DC---------數(shù)據(jù)/命令--------GPB_5
CS---------CS片選-----------GPB_1
*/
static u8 OLED_GPIO_Init(void)
{
	/*1. 將物理地址轉(zhuǎn)換為虛擬地址*/
	GPB_CON=ioremap(0x11400040,4);
	GPB_DAT=ioremap(0x11400044,4);
	if(GPB_CON==NULL||GPB_DAT==NULL)
	{
		printk("物理地址轉(zhuǎn)換為虛擬地址出現(xiàn)問(wèn)題!\n");
		return -1;
	}
	/*2. 配置GPIO口模式*/
	*GPB_CON&=0xFF000F00;
	*GPB_CON|=0x00111011;
	
	/*3. 上拉GPIO口*/
	OLED_CS(1);
	OLED_DC(1);
	OLED_MOSI(1);
	OLED_RES(1);
	OLED_SCK(1);
}
/*
函數(shù)功能: OLED屏幕初始化
*/
static void OLED_Init(void)
{
	/*1. 初始化配置GPIO口*/
	OLED_GPIO_Init();

	/*2. 執(zhí)行OLED屏幕的初始化配置*/
	OLED_RES(1);
	udelay(2000);
	OLED_RES(0);
	udelay(2000);
	OLED_RES(1);
	udelay(2000);
	
	OLED_WriteOneByte(0xAE,OLED_CMD); //0xAE表示關(guān)顯示,0xAF表示開(kāi)顯示

	OLED_WriteOneByte(0x00,OLED_CMD);
	OLED_WriteOneByte(0x10,OLED_CMD);

	OLED_WriteOneByte(0x40,OLED_CMD);

	OLED_WriteOneByte(0xB0,OLED_CMD);

	OLED_WriteOneByte(0x81,OLED_CMD);
	OLED_WriteOneByte(0xCF,OLED_CMD);

	OLED_WriteOneByte(0xA1,OLED_CMD);

	OLED_WriteOneByte(0xA6,OLED_CMD);

	OLED_WriteOneByte(0xA8,OLED_CMD);
	OLED_WriteOneByte(0x3F,OLED_CMD);

	OLED_WriteOneByte(0xC8,OLED_CMD);

	OLED_WriteOneByte(0xD3,OLED_CMD);
	OLED_WriteOneByte(0x00,OLED_CMD);

	OLED_WriteOneByte(0xD5,OLED_CMD);
	OLED_WriteOneByte(0x80,OLED_CMD);

	OLED_WriteOneByte(0xD9,OLED_CMD);
	OLED_WriteOneByte(0xF1,OLED_CMD);

	OLED_WriteOneByte(0xDA,OLED_CMD);
	OLED_WriteOneByte(0x12,OLED_CMD);

	OLED_WriteOneByte(0xDB,OLED_CMD);
	OLED_WriteOneByte(0x30,OLED_CMD);

	OLED_WriteOneByte(0x8D,OLED_CMD);
	OLED_WriteOneByte(0x14,OLED_CMD);

	OLED_WriteOneByte(0xAF,OLED_CMD); //正常模式
}

/*
函數(shù)功能:  寫(xiě)一個(gè)字節(jié)
函數(shù)參數(shù):
		cmd=0表示命令，cmd=1表示數(shù)據(jù)
*/
static void OLED_WriteOneByte(u8 data,u8 cmd)
{
	u8 i;
	/*1. 區(qū)分發(fā)送數(shù)據(jù)是命令還是屏幕數(shù)據(jù)*/
	if(cmd){OLED_DC(1);}
	else {OLED_DC(0);}
	udelay(2);
	
	/*2. 發(fā)送實(shí)際的數(shù)據(jù)*/
	OLED_CS(0); //選中OLED
	
	for(i=0;i<8;i++)
	{
		udelay(2);
		OLED_SCK(0); //告訴從機(jī)，主機(jī)將要發(fā)送數(shù)據(jù)
		if(data&0x80){OLED_MOSI(1);} //發(fā)送數(shù)據(jù)
		else {OLED_MOSI(0);}
		udelay(2);
		OLED_SCK(1); //告訴從機(jī)，主機(jī)數(shù)據(jù)發(fā)送完畢
		data<<=1;   //繼續(xù)發(fā)送下一位數(shù)據(jù)
	}
	
	OLED_CS(1);  //取消選中OLED
	OLED_SCK(1); //上拉時(shí)鐘線，恢復(fù)空閑電平
}
/*
函數(shù)功能: 清屏 (開(kāi)全部燈、關(guān)全部燈)
*/
static void OLED_Clear(u8 data)
{
	u8 i,j;
	for(i=0;i<8;i++)
	{
		OLED_WriteOneByte(0xB0+i,OLED_CMD); //設(shè)置頁(yè)地址
		OLED_WriteOneByte(0x10,OLED_CMD);   //設(shè)置列高起始地址(半字節(jié))
		OLED_WriteOneByte(0x00,OLED_CMD);   //設(shè)置列低起始地址(半字節(jié))
		for(j=0;j<128;j++)
		{
			OLED_WriteOneByte(data,OLED_DAT); //寫(xiě)數(shù)據(jù)
		}
	}
}

/*
定義顯存數(shù)組:  8行，每行128列，與OLED屏幕對(duì)應(yīng)
*/
static u8 OLED_GRAM[8][128]; 

/*
函數(shù)功能: 畫(huà)點(diǎn)函數(shù)
		x: 橫向坐標(biāo)0~128
		y: 縱坐標(biāo)0~64	
		c: 1表示亮、0表示滅
*/
static void OLED_DrawPoint(u8 x,u8 y,u8 c)
{
	u8 page;
	page=y/8; //得到當(dāng)前點(diǎn)的頁(yè)數(shù)0/8=0 1/8=0 
	y=y%8;    //得到一列中點(diǎn)的位置。(0~7)
  //0%8=0 1%8=1 .....7%8=7  8%8=0  9%8=1 ......
	if(c) OLED_GRAM[page][x]|=1vm_flags |= VM_RESERVED;//標(biāo)志該內(nèi)存區(qū)不能被換出，在設(shè)備驅(qū)動(dòng)中虛擬頁(yè)和物理頁(yè)的關(guān)系應(yīng)該是長(zhǎng)期的，應(yīng)該保留起來(lái)，不能隨便被別的虛擬頁(yè)換出
	if(remap_pfn_range(vma,//虛擬內(nèi)存區(qū)域，即設(shè)備地址將要映射到這里
						vma->vm_start,//虛擬空間的起始地址
						virt_to_phys(mmap_buffer)>>PAGE_SHIFT,//與物理內(nèi)存對(duì)應(yīng)的頁(yè)幀號(hào)，物理地址右移 12 位
						vma->vm_end - vma->vm_start,//映射區(qū)域大小，一般是頁(yè)大小的整數(shù)倍
						vma->vm_page_prot))//保護(hù)屬性，
	{
		return -EAGAIN;
	}
	
	printk("(drv)映射的長(zhǎng)度:%d\n",vma->vm_end - vma->vm_start);
	printk("物理地址:0x%X\n",virt_to_phys(mmap_buffer));
	/*
		開(kāi)發(fā)板的DDR容量: 1G
		0x40000000 ~ 0x80000000 
		0x10000000=256M
	*/
	return 0;
}

#define _OLED_RefreshGRAM 0x12345 /*將應(yīng)用層的數(shù)據(jù)刷新到OLED屏幕上*/
#define _OLED_ClearGRAM 0x45678 /*將應(yīng)用層的數(shù)據(jù)刷新到OLED屏幕上*/
static int lcd_ioctl(struct fb_info *info, unsigned int cmd,unsigned long arg)
{
	switch(cmd)
	{
		case _OLED_RefreshGRAM:
			 memcpy(OLED_GRAM,mmap_buffer,1024); //拷貝數(shù)據(jù)
			 OLED_RefreshGRAM(); /*刷新*/
			 break;
		case _OLED_ClearGRAM: /*清屏*/
			 OLED_Clear(0);
			 break;
	}
	return 0;
}

static int lcd_release(struct fb_info *info, int user)
{
	if(mmap_buffer!=NULL)
	{
		kfree(mmap_buffer);
	}
	printk("lcd_release調(diào)用成功\n");
	return 0;
}
/*幀緩沖設(shè)備專(zhuān)用的文件操作接口*/
static struct fb_ops fbops=
{
	.fb_open=lcd_open,
	.fb_release=lcd_release,
	.fb_mmap=lcd_mmap,
	.fb_ioctl=lcd_ioctl
};
/*幀緩沖的設(shè)備結(jié)構(gòu)體*/
static struct fb_info lcd_info=
{
	.var= /*可變形參*/
		{
			.xres=128,
			.yres=64,
			.bits_per_pixel=1
		},
	.fix=
		{
			.smem_len=4096,
			.line_length=128
		},
	.fbops=&fbops
};

static int __init tiny4412_oled_init(void)
{
	/*1. 初始化OLED屏幕*/
	OLED_Init();
	OLED_Clear(0);//清屏為黑色
	
	/*2. 幀緩沖驅(qū)動(dòng)注冊(cè)*/
	if(register_framebuffer(&lcd_info)!=0)
	{
		printk("提示: lcd驅(qū)動(dòng)安裝失敗!\n");
		return -1;
	}
	else
	{
		printk("提示: lcd驅(qū)動(dòng)安裝成功!\n");	
	}
	
    return 0;
}
static void __exit tiny4412_oled_exit(void)
{
	/*1. 幀緩沖驅(qū)動(dòng)注銷(xiāo)*/
	if(unregister_framebuffer(&lcd_info)!=0)
	{
		printk("提示: lcd驅(qū)動(dòng)卸載失敗!\n");
		return -1;
	}
	else
	{
		printk("提示: lcd驅(qū)動(dòng)卸載成功!\n");
	}
	
	/*2. 解除虛擬地址映射關(guān)系*/
	iounmap(GPB_CON);
	iounmap(GPB_DAT);
}

module_init(tiny4412_oled_init);  /*指定驅(qū)動(dòng)的入口函數(shù)*/
module_exit(tiny4412_oled_exit);  /*指定驅(qū)動(dòng)的出口函數(shù)*/
MODULE_LICENSE("GPL");      	  /*指定驅(qū)動(dòng)許可證*/
;>

3.2 app.c 應(yīng)用層代碼

#include 
#include 
#include 
#include 
#include 
#include 
#include 

unsigned char *lcd_mem=NULL; /*LCD的內(nèi)存地址*/
struct fb_fix_screeninfo finfo; /*固定形參*/
struct fb_var_screeninfo vinfo; /*可變形參*/
	
unsigned char font[]=
{
/*--  文字:  國(guó)  --*/
/*--  宋體42;  此字體下對(duì)應(yīng)的點(diǎn)陣為：寬x高=56x56   寬/8*高*/
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x01,0xC0,0x00,0x00,0x00,0x07,0x00,0x01,0xFF,0xFF,0xFF,
0xFF,0xFF,0xC0,0x01,0xFF,0xFF,0xFF,0xFF,0xFF,0xE0,0x01,0xF0,0x00,0x00,0x00,0x07,
0xC0,0x01,0xF0,0x00,0x00,0x00,0x07,0x80,0x01,0xF0,0x00,0x00,0x00,0x07,0x80,0x01,
0xF0,0x00,0x00,0x01,0x87,0x80,0x01,0xF0,0x00,0x00,0x03,0xC7,0x80,0x01,0xF7,0xFF,
0xFF,0xFF,0xE7,0x80,0x01,0xF3,0xFF,0xFF,0xFF,0xF7,0x80,0x01,0xF1,0xC0,0x7C,0x00,
0x07,0x80,0x01,0xF0,0x00,0x7C,0x00,0x07,0x80,0x01,0xF0,0x00,0x7C,0x00,0x07,0x80,
0x01,0xF0,0x00,0x7C,0x00,0x07,0x80,0x01,0xF0,0x00,0x7C,0x00,0x07,0x80,0x01,0xF0,
0x00,0x7C,0x00,0x07,0x80,0x01,0xF0,0x00,0x7C,0x00,0x07,0x80,0x01,0xF0,0x00,0x7C,
0x00,0x07,0x80,0x01,0xF0,0x00,0x7C,0x06,0x07,0x80,0x01,0xF0,0x00,0x7C,0x0F,0x07,
0x80,0x01,0xF1,0xFF,0xFF,0xFF,0x87,0x80,0x01,0xF1,0xFF,0xFF,0xFF,0xC7,0x80,0x01,
0xF0,0xF0,0x7C,0x00,0x07,0x80,0x01,0xF0,0x00,0x7C,0x00,0x07,0x80,0x01,0xF0,0x00,
0x7F,0xC0,0x07,0x80,0x01,0xF0,0x00,0x7D,0xF0,0x07,0x80,0x01,0xF0,0x00,0x7C,0xFC,
0x07,0x80,0x01,0xF0,0x00,0x7C,0x7E,0x07,0x80,0x01,0xF0,0x00,0x7C,0x3F,0x07,0x80,
0x01,0xF0,0x00,0x7C,0x3F,0x07,0x80,0x01,0xF0,0x00,0x7C,0x1F,0x07,0x80,0x01,0xF0,
0x00,0x7C,0x0F,0x07,0x80,0x01,0xF0,0x00,0x7C,0x0E,0x07,0x80,0x01,0xF0,0x00,0x7C,
0x07,0x87,0x80,0x01,0xF0,0x00,0x7C,0x03,0xC7,0x80,0x01,0xF0,0x00,0x7C,0x07,0xE7,
0x80,0x01,0xFF,0xFF,0xFF,0xFF,0xF7,0x80,0x01,0xFF,0xFF,0xFF,0xFF,0xFF,0x80,0x01,
0xF7,0x80,0x00,0x00,0x07,0x80,0x01,0xF0,0x00,0x00,0x00,0x07,0x80,0x01,0xF0,0x00,
0x00,0x00,0x07,0x80,0x01,0xF0,0x00,0x00,0x00,0x07,0x80,0x01,0xF0,0x00,0x00,0x00,
0x07,0x80,0x01,0xFF,0xFF,0xFF,0xFF,0xFF,0x80,0x01,0xFF,0xFF,0xFF,0xFF,0xFF,0x80,
0x01,0xF0,0x00,0x00,0x00,0x07,0x80,0x01,0xF0,0x00,0x00,0x00,0x07,0x80,0x01,0xF0,
0x00,0x00,0x00,0x07,0x80,0x01,0xF0,0x00,0x00,0x00,0x07,0x00,0x01,0xC0,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
};

/*
定義顯存數(shù)組:  8行，每行128列，與OLED屏幕對(duì)應(yīng)
*/
static unsigned char OLED_GRAM[8][128]; 

/*
函數(shù)功能: 畫(huà)點(diǎn)函數(shù)
		x: 橫向坐標(biāo)0~128
		y: 縱坐標(biāo)0~64	
		c: 1表示亮、0表示滅
*/
static void OLED_DrawPoint(unsigned char x,unsigned char y,unsigned char c)
{
	unsigned char page;
	page=y/8; //得到當(dāng)前點(diǎn)的頁(yè)數(shù)0/8=0 1/8=0 
	y=y%8;    //得到一列中點(diǎn)的位置。(0~7)
  //0%8=0 1%8=1 .....7%8=7  8%8=0  9%8=1 ......
	if(c) OLED_GRAM[page][x]|=1<;>