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【摘要】 OLED顯示屏在是智能手環，智能手表上用的非常的多，功耗低，不刺眼，優點特別多。本篇文章就介紹,在Linux系統里如何使用OLED顯示屏，要使用OLED顯示屏，大致分為兩步: (1) 針對OLED顯示屏編寫一個驅動 (2) 編寫應用層程序進行測試。

1. 前言

OLED顯示屏在是智能手環，智能手表上用的非常的多，功耗低，不刺眼，優點特別多。本篇文章就介紹,在Linux系統里如何使用OLED顯示屏，要使用OLED顯示屏，大致分為兩步: (1) 針對OLED顯示屏編寫一個驅動 (2) 編寫應用層程序進行測試。

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。

測試開發板采用友善之臂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. 驅動代碼

Linux內核提供了標準SPI子系統框架，和前面介紹的IIC子系統框架使用類似，代碼分為設備端和驅動端，Linux內核提供子系統的目的就是為了統一驅動編寫標準，提高驅動代碼的移植性。

本篇文章代碼沒有采用SPI子系統框架，采用單片機慣用的模擬SPI時序，對入門而言，代碼更容易理解。

3.1 oled.c 驅動示例代碼

#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);}

//命令與數據區分
#define OLED_CMD 0
#define OLED_DAT 1

//函數聲明區域
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);
/*
函數功能: OLED對應的GPIO口初始化
硬件連接:
OLED模塊---Tiny4412開發板
GND--------GND
VCC--------VCC(5V)
D0---------SCL--------------GPB_0
D1---------MOSI-------------GPB_3
RES--------復位-------------GPB_4
DC---------數據/命令--------GPB_5
CS---------CS片選-----------GPB_1
*/
static u8 OLED_GPIO_Init(void)
{
	/*1. 將物理地址轉換為虛擬地址*/
	GPB_CON=ioremap(0x11400040,4);
	GPB_DAT=ioremap(0x11400044,4);
	if(GPB_CON==NULL||GPB_DAT==NULL)
	{
		printk("物理地址轉換為虛擬地址出現問題!\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表示關顯示,0xAF表示開顯示

	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
}

/*
函數功能:  寫一個字節
函數參數:
		cmd=0表示命令，cmd=1表示數據
*/
static void OLED_WriteOneByte(u8 data,u8 cmd)
{
	u8 i;
	/*1. 區分發送數據是命令還是屏幕數據*/
	if(cmd){OLED_DC(1);}
	else {OLED_DC(0);}
	udelay(2);
	
	/*2. 發送實際的數據*/
	OLED_CS(0); //選中OLED
	
	for(i=0;i<8;i++)
	{
		udelay(2);
		OLED_SCK(0); //告訴從機，主機將要發送數據
		if(data&0x80){OLED_MOSI(1);} //發送數據
		else {OLED_MOSI(0);}
		udelay(2);
		OLED_SCK(1); //告訴從機，主機數據發送完畢
		data<<=1;   //繼續發送下一位數據
	}
	
	OLED_CS(1);  //取消選中OLED
	OLED_SCK(1); //上拉時鐘線，恢復空閑電平
}
/*
函數功能: 清屏 (開全部燈、關全部燈)
*/
static void OLED_Clear(u8 data)
{
	u8 i,j;
	for(i=0;i<8;i++)
	{
		OLED_WriteOneByte(0xB0+i,OLED_CMD); //設置頁地址
		OLED_WriteOneByte(0x10,OLED_CMD);   //設置列高起始地址(半字節)
		OLED_WriteOneByte(0x00,OLED_CMD);   //設置列低起始地址(半字節)
		for(j=0;j<128;j++)
		{
			OLED_WriteOneByte(data,OLED_DAT); //寫數據
		}
	}
}

/*
定義顯存數組:  8行，每行128列，與OLED屏幕對應
*/
static u8 OLED_GRAM[8][128]; 

/*
函數功能: 畫點函數
		x: 橫向坐標0~128
		y: 縱坐標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; //得到當前點的頁數0/8=0 1/8=0 
	y=y%8;    //得到一列中點的位置。(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;//標志該內存區不能被換出，在設備驅動中虛擬頁和物理頁的關系應該是長期的，應該保留起來，不能隨便被別的虛擬頁換出
	if(remap_pfn_range(vma,//虛擬內存區域，即設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,//與物理內存對應的頁幀號，物理地址右移 12 位
						vma->vm_end - vma->vm_start,//映射區域大小，一般是頁大小的整數倍
						vma->vm_page_prot))//保護屬性，
	{
		return -EAGAIN;
	}
	
	printk("(drv)映射的長度:%d\n",vma->vm_end - vma->vm_start);
	printk("物理地址:0x%X\n",virt_to_phys(mmap_buffer));
	/*
		開發板的DDR容量: 1G
		0x40000000 ~ 0x80000000 
		0x10000000=256M
	*/
	return 0;
}

#define _OLED_RefreshGRAM 0x12345 /*將應用層的數據刷新到OLED屏幕上*/
#define _OLED_ClearGRAM 0x45678 /*將應用層的數據刷新到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); //拷貝數據
			 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調用成功\n");
	return 0;
}
/*幀緩沖設備專用的文件操作接口*/
static struct fb_ops fbops=
{
	.fb_open=lcd_open,
	.fb_release=lcd_release,
	.fb_mmap=lcd_mmap,
	.fb_ioctl=lcd_ioctl
};
/*幀緩沖的設備結構體*/
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. 幀緩沖驅動注冊*/
	if(register_framebuffer(&lcd_info)!=0)
	{
		printk("提示: lcd驅動安裝失敗!\n");
		return -1;
	}
	else
	{
		printk("提示: lcd驅動安裝成功!\n");	
	}
	
    return 0;
}
static void __exit tiny4412_oled_exit(void)
{
	/*1. 幀緩沖驅動注銷*/
	if(unregister_framebuffer(&lcd_info)!=0)
	{
		printk("提示: lcd驅動卸載失敗!\n");
		return -1;
	}
	else
	{
		printk("提示: lcd驅動卸載成功!\n");
	}
	
	/*2. 解除虛擬地址映射關系*/
	iounmap(GPB_CON);
	iounmap(GPB_DAT);
}

module_init(tiny4412_oled_init);  /*指定驅動的入口函數*/
module_exit(tiny4412_oled_exit);  /*指定驅動的出口函數*/
MODULE_LICENSE("GPL");      	  /*指定驅動許可證*/
;>

3.2 app.c 應用層代碼

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

unsigned char *lcd_mem=NULL; /*LCD的內存地址*/
struct fb_fix_screeninfo finfo; /*固定形參*/
struct fb_var_screeninfo vinfo; /*可變形參*/
	
unsigned char font[]=
{
/*--  文字:  國  --*/
/*--  宋體42;  此字體下對應的點陣為：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,
};

/*
定義顯存數組:  8行，每行128列，與OLED屏幕對應
*/
static unsigned char OLED_GRAM[8][128]; 

/*
函數功能: 畫點函數
		x: 橫向坐標0~128
		y: 縱坐標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; //得到當前點的頁數0/8=0 1/8=0 
	y=y%8;    //得到一列中點的位置。(0~7)
  //0%8=0 1%8=1 .....7%8=7  8%8=0  9%8=1 ......
	if(c) OLED_GRAM[page][x]|=1<;>

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