Linux驱动开发-编写OLED显示屏驱动

【摘要】 OLED显示屏在是智能手环，智能手表上用的非常的多，功耗低，不刺眼，优点特别多。本篇文章就介绍,在Linux系统里如何使用OLED显示屏，要使用OLED显示屏，大致分为两步: (1) 针对OLED显示屏编写一个驱动 (2) 编写应用层程序进行测试。

1. 前言

OLED显示屏在是智能手环，智能手表上用的非常的多，功耗低，不刺眼，优点特别多。本篇文章就介绍,在Linux系统里如何使用OLED显示屏，要使用OLED显示屏，大致分为两步: (1) 针对OLED显示屏编写一个驱动 (2) 编写应用层程序进行测试。

采用的OLED显示屏是0.96寸SPI接口显示屏，分辨率是128*64，比较便宜，淘宝上非常多。

测试开发板采用友善之臂Tiny4412，三星的EXYNOS-4412芯片，4核1.5GHZ，板载8G-EMMC，2G-DDR。

2. 硬件接线效果

3. 驱动代码

Linux内核提供了标准SPI子系统框架，和前面介绍的IIC子系统框架使用类似，代码分为设备端和驱动端，Linux内核提供子系统的目的就是为了统一驱动编写标准，提高驱动代码的移植性。

本篇文章代码没有采用SPI子系统框架，采用单片机惯用的模拟SPI时序，对入门而言，代码更容易理解。

3.1 oled.c 驱动示例代码

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

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

//OLED屏幕底层接口
#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);}

//命令与数据区分
#define OLED_CMD 0
#define OLED_DAT 1

//函数声明区域
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);
/*
函数功能: OLED对应的GPIO口初始化
硬件连接:
OLED模块---Tiny4412开发板
GND--------GND
VCC--------VCC(5V)
D0---------SCL--------------GPB_0
D1---------MOSI-------------GPB_3
RES--------复位-------------GPB_4
DC---------数据/命令--------GPB_5
CS---------CS片选-----------GPB_1
*/
static u8 OLED_GPIO_Init(void)
{
	/*1. 将物理地址转换为虚拟地址*/
	GPB_CON=ioremap(0x11400040,4);
	GPB_DAT=ioremap(0x11400044,4);
	if(GPB_CON==NULL||GPB_DAT==NULL)
	{
		printk("物理地址转换为虚拟地址出现问题!\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);
}
/*
函数功能: OLED屏幕初始化
*/
static void OLED_Init(void)
{
	/*1. 初始化配置GPIO口*/
	OLED_GPIO_Init();

	/*2. 执行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表示关显示,0xAF表示开显示

	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
}

/*
函数功能:  写一个字节
函数参数:
		cmd=0表示命令，cmd=1表示数据
*/
static void OLED_WriteOneByte(u8 data,u8 cmd)
{
	u8 i;
	/*1. 区分发送数据是命令还是屏幕数据*/
	if(cmd){OLED_DC(1);}
	else {OLED_DC(0);}
	udelay(2);
	
	/*2. 发送实际的数据*/
	OLED_CS(0); //选中OLED
	
	for(i=0;i<8;i++)
	{
		udelay(2);
		OLED_SCK(0); //告诉从机，主机将要发送数据
		if(data&0x80){OLED_MOSI(1);} //发送数据
		else {OLED_MOSI(0);}
		udelay(2);
		OLED_SCK(1); //告诉从机，主机数据发送完毕
		data<<=1;   //继续发送下一位数据
	}
	
	OLED_CS(1);  //取消选中OLED
	OLED_SCK(1); //上拉时钟线，恢复空闲电平
}
/*
函数功能: 清屏 (开全部灯、关全部灯)
*/
static void OLED_Clear(u8 data)
{
	u8 i,j;
	for(i=0;i<8;i++)
	{
		OLED_WriteOneByte(0xB0+i,OLED_CMD); //设置页地址
		OLED_WriteOneByte(0x10,OLED_CMD);   //设置列高起始地址(半字节)
		OLED_WriteOneByte(0x00,OLED_CMD);   //设置列低起始地址(半字节)
		for(j=0;j<128;j++)
		{
			OLED_WriteOneByte(data,OLED_DAT); //写数据
		}
	}
}

/*
定义显存数组:  8行，每行128列，与OLED屏幕对应
*/
static u8 OLED_GRAM[8][128]; 

/*
函数功能: 画点函数
		x: 横向坐标0~128
		y: 纵坐标0~64	
		c: 1表示亮、0表示灭
*/
static void OLED_DrawPoint(u8 x,u8 y,u8 c)
{
	u8 page;
	page=y/8; //得到当前点的页数0/8=0 1/8=0 
	y=y%8;    //得到一列中点的位置。(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;//标志该内存区不能被换出，在设备驱动中虚拟页和物理页的关系应该是长期的，应该保留起来，不能随便被别的虚拟页换出
	if(remap_pfn_range(vma,//虚拟内存区域，即设备地址将要映射到这里
						vma->vm_start,//虚拟空间的起始地址
						virt_to_phys(mmap_buffer)>>PAGE_SHIFT,//与物理内存对应的页帧号，物理地址右移 12 位
						vma->vm_end - vma->vm_start,//映射区域大小，一般是页大小的整数倍
						vma->vm_page_prot))//保护属性，
	{
		return -EAGAIN;
	}
	
	printk("(drv)映射的长度:%d\n",vma->vm_end - vma->vm_start);
	printk("物理地址:0x%X\n",virt_to_phys(mmap_buffer));
	/*
		开发板的DDR容量: 1G
		0x40000000 ~ 0x80000000 
		0x10000000=256M
	*/
	return 0;
}

#define _OLED_RefreshGRAM 0x12345 /*将应用层的数据刷新到OLED屏幕上*/
#define _OLED_ClearGRAM 0x45678 /*将应用层的数据刷新到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); //拷贝数据
			 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调用成功\n");
	return 0;
}
/*帧缓冲设备专用的文件操作接口*/
static struct fb_ops fbops=
{
	.fb_open=lcd_open,
	.fb_release=lcd_release,
	.fb_mmap=lcd_mmap,
	.fb_ioctl=lcd_ioctl
};
/*帧缓冲的设备结构体*/
static struct fb_info lcd_info=
{
	.var= /*可变形参*/
		{
			.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);//清屏为黑色
	
	/*2. 帧缓冲驱动注册*/
	if(register_framebuffer(&lcd_info)!=0)
	{
		printk("提示: lcd驱动安装失败!\n");
		return -1;
	}
	else
	{
		printk("提示: lcd驱动安装成功!\n");	
	}
	
    return 0;
}
static void __exit tiny4412_oled_exit(void)
{
	/*1. 帧缓冲驱动注销*/
	if(unregister_framebuffer(&lcd_info)!=0)
	{
		printk("提示: lcd驱动卸载失败!\n");
		return -1;
	}
	else
	{
		printk("提示: lcd驱动卸载成功!\n");
	}
	
	/*2. 解除虚拟地址映射关系*/
	iounmap(GPB_CON);
	iounmap(GPB_DAT);
}

module_init(tiny4412_oled_init);  /*指定驱动的入口函数*/
module_exit(tiny4412_oled_exit);  /*指定驱动的出口函数*/
MODULE_LICENSE("GPL");      	  /*指定驱动许可证*/
;>

3.2 app.c 应用层代码

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

unsigned char *lcd_mem=NULL; /*LCD的内存地址*/
struct fb_fix_screeninfo finfo; /*固定形参*/
struct fb_var_screeninfo vinfo; /*可变形参*/
	
unsigned char font[]=
{
/*--  文字:  国  --*/
/*--  宋体42;  此字体下对应的点阵为：宽x高=56x56   宽/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,
};

/*
定义显存数组:  8行，每行128列，与OLED屏幕对应
*/
static unsigned char OLED_GRAM[8][128]; 

/*
函数功能: 画点函数
		x: 横向坐标0~128
		y: 纵坐标0~64	
		c: 1表示亮、0表示灭
*/
static void OLED_DrawPoint(unsigned char x,unsigned char y,unsigned char c)
{
	unsigned char page;
	page=y/8; //得到当前点的页数0/8=0 1/8=0 
	y=y%8;    //得到一列中点的位置。(0~7)
  //0%8=0 1%8=1 .....7%8=7  8%8=0  9%8=1 ......
	if(c) OLED_GRAM[page][x]|=1<;>