I2C总线驱动：裸机版、应用层的使用、二级外设驱动三种方法

一、I2C总线背景知识

SOC芯片平台的外设分为：

1. 一级外设：外设控制器集成在SOC芯片内部
2. 二级外设：外设控制器由另一块芯片负责，通过一些通讯总线与SOC芯片相连
   
   Inter-Integrated Circuit： 字面意思是用于“集成电路之间”的通信总线，简写：IIC(或者I2C)

i2c传输的要点就是： 传输一个字节 后面必然紧跟一个"响应"信号----应答信号.这个响应信号可能来自主机，或者是从机，具体是谁，就要看传输方向。
传输方向分两种情况(每种情况又有两种可能: A无应答和 B有应答)：

1.主机->从机，主机对从机发一个字节之后，主机要读取从机的响应信号(主机读SDA线)

A) 主机读SDA为高电平，说明从机无应答（意味着从机接收完毕，主机发送停止信号）
B) 主机读SDA为低电平，说明从机有应答。（可继续发送下一个字节）

2.从机->主机， 主机读取从机一个字节之后，主机要向从机发送一个响应信号(主机写SDA线)

A) 主机写SDA为高电平，从机收到主机的无应答信号之后，从机停止传输，等待主机的停止信号。
​B) 主机写SDA为低电平，从机收到主机的应答信号之后，从机继续输出下一字节

二、Exynos4412 I2C收发实现之裸机版

I2CCON寄存器：控制寄存器

第7位：决定是否允许产生应答信号，无论发送还是接收前，需置1

第6位：传输时时钟线分频，一般选置1

第5位：决定是否开启发送或接收结束时发通知，无论发送还是接收前，需置1

第4位：接收或发送是否完毕可以通过检查此位是否为1，接收或发送完毕后需置0

I2CSTAT寄存器：状态寄存器

第6、7位：每次传输前需选择传输模式

第5位：置0产生将产生终止信号，传输前置1产生起始信号

第4位：使能数据输出，传输前需置1

I2CDS寄存器：数据寄存器，发送前被发送的数据存放处，接收后结果也从此处读取

2.1 发送

void iic_write (unsigned char slave_addr, unsigned char addr, unsigned char data)
{// 从设备寻址I2C5.I2CDS = slave_addr;I2C5.I2CCON = 1<<7 | 1<<6 | 1<<5; /* 启用 ACK 位, 预分频器: 512, 启用 RX/TX */I2C5.I2CSTAT = 0x3 << 6 | 1<<5 | 1<<4; /* 主传输模式, 启动, 启用 RX/TX */while(!(I2C5.I2CCON & (1<<4)));I2C5.I2CDS = addr;I2C5.I2CCON &= ~(1<<4); // 清除挂起位以恢复while(!(I2C5.I2CCON & (1<<4)));// 发送数据I2C5.I2CDS = data; // 数据I2C5.I2CCON &= ~(1<<4); // 清除挂起位以恢复while(!(I2C5.I2CCON & (1<<4)));I2C5.I2CSTAT = 0xD0; // 停止I2C5.I2CCON &= ~(1<<4); // 清除挂起位以恢复mydelay_ms(10);
}

2.2 接收

void iic_read(unsigned char slave_addr, unsigned char addr, unsigned char *data)
{// 从设备寻址I2C5.I2CDS = slave_addr;I2C5.I2CCON = 1<<7 | 1<<6 | 1<<5; /* 启用 ACK 位, 预分频器: 512, 启用 RX/TX 中断使能 */I2C5.I2CSTAT = 0x3 << 6 | 1<<5 | 1<<4; /* 主传输模式, 启动, 启用 RX/TX */while(!(I2C5.I2CCON & (1<<4))); /* 对应位为1表示slave_addr传输完成，线路处于挂起状态 */I2C5.I2CDS = addr;I2C5.I2CCON &= ~(1<<4); // 清除挂起位以继续传输while(!(I2C5.I2CCON & (1<<4)));I2C5.I2CSTAT = 0xD0; // 停止  第5位写0，表示要求产生stop信号// 接收数据I2C5.I2CDS = slave_addr | 0x01; // 读取I2C5.I2CCON = 1<<7 | 1<<6 | 1<<5; /* 启用 ACK 位, 预分频器: 512, 启用 RX/TX 中断使能 */I2C5.I2CSTAT = 2<<6 | 1<<5 | 1<<4; /* 主接收模式, 启动, 启用 RX/TX, 0xB0 */while(!(I2C5.I2CCON & (1<<4)));I2C5.I2CCON &= ~((1<<7) | (1<<4)); /* 恢复操作 & 无 ACK */while(!(I2C5.I2CCON & (1<<4)));I2C5.I2CSTAT = 0x90; // 停止  第5位写0，表示要求产生stop信号I2C5.I2CCON &= ~(1<<4); /* 清除中断挂起位 */*data = I2C5.I2CDS;mydelay_ms(10);
}

三、Linux内核对I2C总线的支持

I2C设备驱动（driver驱动层）：即挂接在I2C总线上的二级外设的驱动，也称客户（client）驱动，实现对二级外设的各种操作，二级外设的几乎所有操作全部依赖于对其自身内部寄存器的读写，对这些二级外设寄存器的读写又依赖于I2C总线的发送和接收

I2C总线驱动（访问抽象层、硬件实现控制层）：即对I2C总线自身控制器的驱动，一般SOC芯片都会提供多个I2C总线控制器，每个I2C总线控制器提供一组I2C总线（SDA一根+SCL一根），每一组被称为一个I2C通道，Linux内核里将I2C总线控制器叫做适配器（adapter），适配器驱动主要工作就是提供通过本组I2C总线与二级外设进行数据传输的接口，每个二级外设驱动里必须能够获得其对应的adapter对象才能实现数据传输

I2C核心：承上启下，为I2C设备驱动和I2C总线驱动开发提供接口，为I2C设备驱动层提供管理多个i2c_driver、i2c_client对象的数据结构，为I2C总线驱动层提供多个i2c_algorithm、i2c_adapter对象的数据结构

四大核心对象之间的关系图

i2c二级外设驱动开发涉及到核心结构体及其相关接口函数：

struct i2c_board_info {char        type[I2C_NAME_SIZE];unsigned short  flags;unsigned short  addr;void        *platform_data;struct dev_archdata *archdata;struct device_node *of_node;int     irq;
};
/*用来协助创建i2c_client对象
重要成员
type：用来初始化i2c_client结构中的name成员
flags：用来初始化i2c_client结构中的flags成员
addr：用来初始化i2c_client结构中的addr成员
platform_data：用来初始化i2c_client结构中的.dev.platform_data成员
archdata：用来初始化i2c_client结构中的.dev.archdata成员
irq:用来初始化i2c_client结构中的irq成员关键就是记住该结构和i2c_client结构成员的对应关系。在i2c子系统不直接创建i2c_client结构，只是提供struct i2c_board_info结构信息，让子系统动态创建，并且注册。
*/

struct i2c_client {unsigned short flags;unsigned short addr;char name[I2C_NAME_SIZE];struct i2c_adapter *adapter;struct i2c_driver *driver;struct device dev;int irq;struct list_head detected;
};
/*重要成员：
flags:地址长度，如是10位还是7位地址，默认是7位地址。如果是10位地址器件，则设置为I2C_CLIENT_TEN
addr：具体I2C器件如(at24c02)，设备地址,低7位
name:设备名，用于和i2c_driver层匹配使用的，可以和平台模型中的平台设备层platform_driver中的name作用是一样的。
adapter:本设备所绑定的适配器结构(CPU有很多I2C适配器，类似单片机有串口1、串口2等等，在linux中每个适配器都用一个结构描述)
driver：指向匹配的i2c_driver结构，不需要自己填充，匹配上后内核会完成这个赋值操作
dev:内嵌的设备模型，可以使用其中的platform_data成员传递给任何数据给i2c_driver使用。
irq：设备需要使用到中断时，把中断编号传递给i2c_driver进行注册中断，如果没有就不需要填充。(有的I2C器件有中断引脚编号，与CPU相连)
*//* 获得/释放 i2c_adapter 路径：i2c-core.c linux-3.5\drivers\i2c */
/*功能：通过i2c总线编号获得内核中的i2c_adapter结构地址，然后用户可以使用这个结构地址就可以给i2c_client结构使用，从而实现i2c_client进行总线绑定，从而增加适配器引用计数。
返回值：
NULL：没有找到指定总线编号适配器结构
非NULL：指定nr的适配器结构内存地址*/
struct i2c_adapter *i2c_get_adapter(int nr);/*减少引用计数：当使用·i2c_get_adapter·后，需要使用该函数减少引用计数。（如果你的适配器驱动不需要卸载，可以不使用）*/
void i2c_put_adapter(struct i2c_adapter *adap);/*
功能：根据参数adap，info，addr，addr_list动态创建i2c_client并且进行注册
参数：
adap：i2c_client所依附的适配器结构地址
info：i2c_client基本信息
addt_list: i2c_client的地址(地址定义形式是固定的，一般是定义一个数组，数组必须以I2C_CLIENT_END结束，示例：unsigned short ft5x0x_i2c[]={0x38,I2C_CLIENT_END};
probe:回调函数指针，当创建好i2c_client后，会调用该函数，一般没有什么特殊需求传递NULL。
返回值：
非NULL:创建成功，返回创建好的i2c_client结构地址
NULL：创建失败
*/
struct i2c_client * i2c_new_probed_device
(struct i2c_adapter *adap,struct i2c_board_info *info,unsigned short const *addr_list,int (*probe)(struct i2c_adapter *, unsigned short addr)
);
/*示例：
struct i2c_adapter *ad;
struct i2c_board_info info={""};unsigned short addr_list[]={0x38,0x39,I2C_CLIENT_END};//假设设备挂在i2c-2总线上
ad=i2c_get_adapter(2);//自己填充board_info 
strcpy(inf.type,"xxxxx");
info.flags=0;
//动态创建i2c_client并且注册
i2c_new_probed_device(ad,&info,addr_list,NULL);i2c_put_adapter(ad);
*//*注销*/
void i2c_unregister_device(struct i2c_client *pclt)struct i2c_client * i2c_new_device(struct i2c_adapter *padap,struct i2c_board_info const *pinfo);
/*示例：
struct i2c_adapter *ad;
struct i2c_board_info info={I2C_BOARD_INFO(name,二级外设地址)
};
//假设设备挂在i2c-2总线上
ad=i2c_get_adapter(2);//动态创建i2c_client并且注册
i2c_new_device(ad,&info);i2c_put_adapter(ad);
*/

struct i2c_driver {unsigned int class;/* 标准驱动模型接口 */int (*probe)(struct i2c_client *, const struct i2c_device_id *);int (*remove)(struct i2c_client *);/* 与枚举无关的驱动模型接口 */void (*shutdown)(struct i2c_client *);int (*suspend)(struct i2c_client *, pm_message_t mesg);int (*resume)(struct i2c_client *);void (*alert)(struct i2c_client *, unsigned int data);/* 类似ioctl的命令，可用于执行特定功能 */int (*command)(struct i2c_client *client, unsigned int cmd, void *arg);struct device_driver driver;const struct i2c_device_id *id_table;/* 用于自动设备创建的设备检测回调 */int (*detect)(struct i2c_client *, struct i2c_board_info *);const unsigned short *address_list;struct list_head clients;
};
/* 重要成员：
probe：在i2c_client与i2c_driver匹配后执行该函数
remove：在取消i2c_client与i2c_driver匹配绑定后执行该函数
driver：这个成员类型在平台设备驱动层中也有，而且使用其中的name成员来实现平台设备匹配，但是i2c子系统中不使用其中的name进行匹配，这也是i2c设备驱动模型和平台设备模型匹配方法的一点区别
id_table:用来实现i2c_client与i2c_driver匹配绑定，当i2c_client中的name成员和i2c_driver中id_table中name成员相同的时候，就匹配上了。补充：i2c_client与i2c_driver匹配问题
- i2c_client中的name成员和i2c_driver中id_table中name成员相同的时候
- i2c_client指定的信息在物理上真实存放对应的硬件，并且工作是正常的才会绑定上，并执行其中的probe接口函数这第二点要求和平台模型匹配有区别，平台模型不要求设备层指定信息在物理上真实存在就能匹配
*//* 功能：向内核注册一个i2c_driver对象
返回值：0成功，负数 失败*/
#define i2c_add_driver(driver)     i2c_register_driver(THIS_MODULE, driver)
int i2c_register_driver(struct module *owner, struct i2c_driver *driver);/* 功能：从内核注销一个i2c_driver对象
返回值：无 */
void i2c_del_driver(struct i2c_driver *driver);

struct i2c_msg {__u16 addr; /* slave address            */__u16 flags;
#define I2C_M_TEN       0x0010  /* this is a ten bit chip address */
#define I2C_M_RD        0x0001  /* read data, from slave to master */__u16 len;      /* msg length               */__u8 *buf;      /* pointer to msg data          */
};
/* 重要成员：
addr:要读写的二级外设地址
flags：表示地址的长度，读写功能。如果是10位地址必须设置I2C_M_TEN，如果是读操作必须设置有I2C_M_RD······，可以使用或运算合成。
buf：要读写的数据指针。写操作：数据源 读操作：指定存放数据的缓存区
len：读写数据的数据长度
*//*i2c收发一体化函数,收还是发由参数msgs的成员flags决定*/
int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
/*
功能：根据msgs进行手法控制
参数：
adap：使用哪一个适配器发送信息，一般是取i2c_client结构中的adapter指针作为参数
msgs：具体发送消息指针，一般情况下是一个数组
num:表示前一个参数msgs数组有多少个消息要发送的
返回值：
负数：失败
> 0 表示成功发送i2c_msg数量
*//*I2C读取数据函数*/
int i2c_master_recv(const struct i2c_client *client, char *buf, int count)
/*功能：实现标准的I2C读时序，数据可以是N个数据，这个函数调用时候默认已经包含发送从机地址+读方向这一环节了
参数：
client：设备结构
buf：读取数据存放缓冲区
count：读取数据大小 不大于64k
返回值：
失败：负数
成功：成功读取的字节数
*//*I2C发送数据函数*/
int i2c_master_send(const struct i2c_client *client, const char *buf, int count)
/*功能：实现标准的I2C写时序，数据可以是N个数据，这个函数调用时候默认已经包含发送从机地址+写方向这一环节了
参数：
client：设备结构地址
buf：发送数据存放缓冲区
count：发送数据大小 不大于64k
返回值：
失败：负数
成功：成功发送的字节数
*/

四、MPU6050

三轴角速度+三轴加速度+温度传感器

#define SMPLRT_DIV  0x19 //陀螺仪采样率，典型值：0x07(125Hz)
#define CONFIG   0x1A //低通滤波频率，典型值：0x06(5Hz)
#define GYRO_CONFIG  0x1B //陀螺仪自检及测量范围，典型值：0xF8(不自检，+/-2000deg/s)
#define ACCEL_CONFIG 0x1C //加速计自检、测量范围，典型值：0x19(不自检，+/-G)
#define ACCEL_XOUT_H 0x3B
#define ACCEL_XOUT_L 0x3C
#define ACCEL_YOUT_H 0x3D
#define ACCEL_YOUT_L 0x3E
#define ACCEL_ZOUT_H 0x3F
#define ACCEL_ZOUT_L 0x40
#define TEMP_OUT_H  0x41
#define TEMP_OUT_L  0x42
#define GYRO_XOUT_H  0x43
#define GYRO_XOUT_L  0x44
#define GYRO_YOUT_H  0x45
#define GYRO_YOUT_L  0x46
#define GYRO_ZOUT_H  0x47
#define GYRO_ZOUT_L  0x48
#define PWR_MGMT_1  0x6B //电源管理，典型值：0x00(正常启用)

五、应用层直接使用I2C通道

5.1 预备工作：

5.1.1 exynos4412平台每个i2c通道的信息是通过设备树提供的，因此需要首先在exynos4412-fs4412.dts中增加5通道的节点：

不要忘记：

1. 回内核源码顶层目录执行：make dtbs
2. 将新生成的dtb拷贝到/tftpboot

5.1.2 i2c总线驱动层提供了一个字符设备驱动，以便于应用层可以直接通过它去使用i2c总线通讯去操作二级外设，但需要

内核编译时添加此字符设备驱动代码(i2c-dev.c),因此需要修改make menuconfig的配置：

不要忘记：

1. 回内核源码顶层目录执行：make uImage
2. 将新生成的uImage拷贝到/tftpboot

5.2 应用层直接使用i2c总线的代码实现

缺点：

1. 需要应用程序开发人员查阅原理图和芯片手册，增加了他们的开发负担
2. 开发出的应用程序缺乏可移植性

5.2.1 调用read、write实现接收、发送

mpu6050.h

#ifndef MPU_6050_H
#define MPU_6050_H#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>int init_mpu6050(int fd);
int read_accelx(int fd);
int read_accely(int fd);
int read_accelz(int fd);
int read_temp(int fd);
int read_gyrox(int fd);
int read_gyroy(int fd);
int read_gyroz(int fd);/****************MPU6050内部寄存器地址****************/#define	SMPLRT_DIV		0x19	//陀螺仪采样率，典型值：0x07(125Hz)
#define	CONFIG			0x1A	//低通滤波频率，典型值：0x06(5Hz)
#define	GYRO_CONFIG		0x1B	//陀螺仪自检及测量范围，典型值：0x18(不自检，2000deg/s)
#define	ACCEL_CONFIG	0x1C	//加速计自检、测量范围及高通滤波频率，典型值：0x18(不自检，2G，5Hz)
#define	ACCEL_XOUT_H	0x3B
#define	ACCEL_XOUT_L	0x3C
#define	ACCEL_YOUT_H	0x3D
#define	ACCEL_YOUT_L	0x3E
#define	ACCEL_ZOUT_H	0x3F
#define	ACCEL_ZOUT_L	0x40
#define	TEMP_OUT_H		0x41
#define	TEMP_OUT_L		0x42
#define	GYRO_XOUT_H		0x43
#define	GYRO_XOUT_L		0x44
#define	GYRO_YOUT_H		0x45
#define	GYRO_YOUT_L		0x46
#define	GYRO_ZOUT_H		0x47
#define	GYRO_ZOUT_L		0x48
#define	PWR_MGMT_1		0x6B	//电源管理，典型值：0x00(正常启用)
#define	WHO_AM_I		0x75	//IIC地址寄存器(默认数值0x68，只读)
#define	SlaveAddress	0x68	//MPU6050-I2C地址#define I2C_SLAVE	0x0703	/* Use this slave address */
#define I2C_TENBIT	0x0704	/* 0 for 7 bit addrs, != 0 for 10 bit */#endif

mpu6050_op_rw.c

#include "mpu6050.h"// 从MPU6050读取数据的函数
static int read_data_from_mpu6050(int fd, unsigned char reg, unsigned char *pdata)
{int ret = 0;unsigned char buf[1] = {reg};  // 准备要写入的寄存器地址// 写入要读取的寄存器地址ret = write(fd, buf, 1);if (ret != 1){printf("write reg failed, in read_data_from_mpu6050\n");return -1;  // 写入失败，返回错误}buf[0] = 0;// 读取数据ret = read(fd, buf, 1);if (ret != 1){printf("read data failed, in read_data_from_mpu6050\n");return -1;  // 读取失败，返回错误}*pdata = buf[0];  // 将读取的数据存储到 pdata 中return 0;  // 成功读取数据，返回0
}// 向MPU6050写入数据的函数
static int write_data_to_mpu6050(int fd, unsigned char reg, unsigned char data)
{unsigned char buf[2] = {reg, data};  // 准备要写入的寄存器地址和数据int ret = 0;// 写入数据ret = write(fd, buf, 2);if (ret != 2){printf("write data failed, in write_data_to_mpu6050\n");return -1;  // 写入失败，返回错误}return 0;  // 成功写入数据，返回0
}// 初始化MPU6050的函数
int init_mpu6050(int fd)
{int ret = 0;// 使用ioctl配置I2C设备，将 I2C 设备配置为使用 7 位地址模式ret = ioctl(fd, I2C_TENBIT, 0);if (ret < 0){printf("ioctl I2C_TENBIT failed, in init_mpu6050\n");return -1;  // 配置失败，返回错误}//设置I2C从设备地址，将 I2C 设备的从设备地址设置为 0x68ret = ioctl(fd, I2C_SLAVE, 0x68);if (ret < 0){printf("ioctl I2C_TENBIT failed, in init_mpu6050\n");return -1;  // 配置失败，返回错误}// 向MPU6050写入初始化数据，设置各个寄存器的值ret = write_data_to_mpu6050(fd, PWR_MGMT_1, 0x00);ret += write_data_to_mpu6050(fd, SMPLRT_DIV, 0x07);ret += write_data_to_mpu6050(fd, ACCEL_CONFIG, 0x19);ret += write_data_to_mpu6050(fd, GYRO_CONFIG, 0xF8);if (ret < 0){printf("write init data to mpu6050 failed, in init_mpu6050\n");return -1;  // 写入初始化数据失败，返回错误}return 0;  // 初始化成功，返回0
}// 读取MPU6050加速度计X轴数据的函数
int read_accelx(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;// 从MPU6050读取低位数据ret = read_data_from_mpu6050(fd, ACCEL_XOUT_L, &d);val = d;// 从MPU6050读取高位数据ret = read_data_from_mpu6050(fd, ACCEL_XOUT_H, &d);val |= d << 8;if (ret < 0){printf("read accel x value failed, in read_accelx\n");return -1;  // 读取失败，返回错误}else{return val;  // 返回读取到的加速度计X轴数据}
}
int read_accely(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,ACCEL_YOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,ACCEL_YOUT_H,&d);val |= d << 8;if(ret < 0){printf("read accel y value failed,in read_accely\n");return -1;}else{return val;}
}int read_accelz(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,ACCEL_ZOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,ACCEL_ZOUT_H,&d);val |= d << 8;if(ret < 0){printf("read accel z value failed,in read_accelz\n");return -1;}else{return val;}
}int read_temp(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,TEMP_OUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,TEMP_OUT_H,&d);val |= d << 8;if(ret < 0){printf("read temp value failed,in read_temp\n");return -1;}else{return val;}
}int read_gyrox(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,GYRO_XOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,GYRO_XOUT_H,&d);val |= d << 8;if(ret < 0){printf("read gyro x value failed,in read_gyrox\n");return -1;}else{return val;}
}int read_gyroy(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,GYRO_YOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,GYRO_YOUT_H,&d);val |= d << 8;if(ret < 0){printf("read gyro y value failed,in read_gyroy\n");return -1;}else{return val;}
}int read_gyroz(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,GYRO_ZOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,GYRO_ZOUT_H,&d);val |= d << 8;if(ret < 0){printf("read gyro z value failed,in read_gyroz\n");return -1;}else{return val;}
}

main.c

#include "mpu6050.h"int main(int argc, char *argv[])
{int fd = -1;if(argc < 2) {printf("Argument is too few\n");return 0;}/* open */fd = open(argv[1], O_RDWR);if(fd < 0) {printf("open %s failed\n", argv[1]);return -1;}/* init mpu6050 */init_mpu6050(fd);while(1) {sleep(2);/* read and printf data from mpu6050 */printf("Accel-X : 0x%x\n", read_accelx(fd));printf("Accel-Y : 0x%x\n", read_accely(fd));printf("Accel-Z : 0x%x\n", read_accelz(fd));printf("Temp : 0x%x\n", read_temp(fd));printf("Gyrox-X : 0x%x\n", read_gyrox(fd));printf("Gyroy-X : 0x%x\n", read_gyroy(fd));printf("Gyroz-X : 0x%x\n", read_gyroz(fd));}/* close */close(fd);fd = -1;return 0;
}

5.2.2 调用ioctl实现接收、发送

mpu6050.h

#ifndef MPU_6050_H
#define MPU_6050_H#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>#include <stdio.h>
#include <stdlib.h>
#include <string.h>int init_mpu6050(int fd);
int read_accelx(int fd);
int read_accely(int fd);
int read_accelz(int fd);
int read_temp(int fd);
int read_gyrox(int fd);
int read_gyroy(int fd);
int read_gyroz(int fd);#define SMPLRT_DIV 0x19
#define CONFIG 0x1A
#define GYRO_CONFIG 0x1B
#define ACCEL_CONFIG 0x1C#define ACCEL_XOUT_H 0x3B
#define ACCEL_XOUT_L 0x3C
#define ACCEL_YOUT_H 0x3D
#define ACCEL_YOUT_L 0x3E
#define ACCEL_ZOUT_H 0x3F
#define ACCEL_ZOUT_L 0x40
#define TEMP_OUT_H 0x41
#define TEMP_OUT_L 0x42
#define GYRO_XOUT_H 0x43
#define GYRO_XOUT_L 0x44
#define GYRO_YOUT_H 0x45
#define GYRO_YOUT_L 0x46
#define GYRO_ZOUT_H 0x47
#define GYRO_ZOUT_L 0x48#define PWR_MGMT_1  0x6B#define I2C_SLAVE	0x0703	/* 使用此从设备地址 */
#define I2C_TENBIT	0x0704	/* 0 表示 7 位地址，非 0 表示 10 位地址 */
#define I2C_RDWR	0x0707	/* 组合的读/写传输（只有一个 STOP） */struct i2c_msg {unsigned short addr;	/* 从设备地址 */unsigned short flags;
#define I2C_M_TEN		0x0010	/* 这是十位地址的芯片地址 */
#define I2C_M_RD		0x0001	/* 读取数据，从从设备传输到主设备 */unsigned short len;		/* 消息长度 */unsigned char *buf;		/* 指向消息数据的指针 */
};/* 此结构在 I2C_RDWR ioctl 调用中使用 */
struct i2c_rdwr_ioctl_data {struct i2c_msg *msgs;	/* 指向 i2c_msg 的指针 */unsigned int nmsgs;	/* i2c_msg 的数量 */
};
#endif

mpu6050_op_ioctl.c

#include "mpu6050.h"static int read_data_from_mpu6050(int fd,unsigned char slave,unsigned char reg,unsigned char *pdata)
{struct i2c_rdwr_ioctl_data work = {NULL};struct i2c_msg msgs[2] = {{0}};unsigned char buf1[1] = {reg};unsigned char buf2[1] = {0};int ret = 0;work.msgs = msgs;work.nmsgs = 2;msgs[0].addr = slave;msgs[0].flags = 0;msgs[0].buf = buf1;msgs[0].len = 1;msgs[1].addr = slave;msgs[1].flags = I2C_M_RD;msgs[1].buf = buf2;msgs[1].len = 1;ret = ioctl(fd,I2C_RDWR,&work);if(ret < 0){printf("ioctl I2C_RDWR failed,in read_data_from_mpu6050\n");return -1;}else{*pdata = buf2[0];return 0;}
}static int write_data_to_mpu6050(int fd,unsigned char slave,unsigned char reg,unsigned char data)
{struct i2c_rdwr_ioctl_data work = {NULL};struct i2c_msg msg = {0};unsigned char buf[2] = {reg,data};int ret = 0;work.msgs = &msg;work.nmsgs = 1;msg.addr = slave;msg.flags = 0;msg.buf = buf;msg.len = 2;ret = ioctl(fd,I2C_RDWR,&work);if(ret < 0){printf("ioctl I2C_RDWR failed,in write_data_to_mpu6050\n");return -1;}else{return 0;}
}int init_mpu6050(int fd)
{int ret = 0;ret = ioctl(fd,I2C_TENBIT,0);if(ret < 0){printf("ioctl I2C_TENBIT failed,in init_mpu6050\n");return -1;}ret = ioctl(fd,I2C_SLAVE,0x68);if(ret < 0){printf("ioctl I2C_TENBIT failed,in init_mpu6050\n");return -1;}ret = write_data_to_mpu6050(fd,0x68,PWR_MGMT_1,0x00);ret += write_data_to_mpu6050(fd,0x68,SMPLRT_DIV,0x07);ret += write_data_to_mpu6050(fd,0x68,ACCEL_CONFIG,0x19);ret += write_data_to_mpu6050(fd,0x68,GYRO_CONFIG,0xF8);if(ret < 0){printf("write init data to mpu6050 failed,in init_mpu6050\n");return -1;}return 0;
}int read_accelx(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,ACCEL_XOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,ACCEL_XOUT_H,&d);val |= d << 8;if(ret < 0){printf("read accel x value failed,in read_accelx\n");return -1;}else{return val;}
}int read_accely(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,ACCEL_YOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,ACCEL_YOUT_H,&d);val |= d << 8;if(ret < 0){printf("read accel y value failed,in read_accely\n");return -1;}else{return val;}
}int read_accelz(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,ACCEL_ZOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,ACCEL_ZOUT_H,&d);val |= d << 8;if(ret < 0){printf("read accel z value failed,in read_accelz\n");return -1;}else{return val;}
}int read_temp(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,TEMP_OUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,TEMP_OUT_H,&d);val |= d << 8;if(ret < 0){printf("read temp value failed,in read_temp\n");return -1;}else{return val;}
}int read_gyrox(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,GYRO_XOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,GYRO_XOUT_H,&d);val |= d << 8;if(ret < 0){printf("read gyro x value failed,in read_gyrox\n");return -1;}else{return val;}
}int read_gyroy(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,GYRO_YOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,GYRO_YOUT_H,&d);val |= d << 8;if(ret < 0){printf("read gyro y value failed,in read_gyroy\n");return -1;}else{return val;}
}int read_gyroz(int fd)
{unsigned short val = 0;unsigned char d = 0;int ret = 0;ret = read_data_from_mpu6050(fd,0x68,GYRO_ZOUT_L,&d);val = d;ret = read_data_from_mpu6050(fd,0x68,GYRO_ZOUT_H,&d);val |= d << 8;if(ret < 0){printf("read gyro z value failed,in read_gyroz\n");return -1;}else{return val;}
}

main.c

#include "mpu6050.h"int main(int argc,char *argv[])
{int fd = -1;if(argc < 2){printf("Argument is too few\n");return 1;}/*open*/fd = open(argv[1],O_RDWR);if(fd < 0){printf("open %s failed\n",argv[1]);return 2;}/*init mpu6050*/init_mpu6050(fd);while(1){sleep(2);/*read and print data from 6050*/printf("Accel-X:0x%x\n",read_accelx(fd));printf("Accel-Y:0x%x\n",read_accely(fd));printf("Accel-Z:0x%x\n",read_accelz(fd));printf("Temp:0x%x\n",read_temp(fd));printf("GYRO-X:0x%x\n",read_gyrox(fd));printf("GYRO-Y:0x%x\n",read_gyroy(fd));printf("GYRO-z:0x%x\n",read_gyroz(fd));printf("\n");}/*close*/close(fd);fd = -1;return 0;
}

六、I2C总线二级外设驱动开发方法

1. 查阅原理图以便得知二级外设挂在哪条I2C总线上、二级外设的身份标识（二级外设自身的地址）

2. 参照platform样式搭建二级外设驱动框架

3. 查询二级外设芯片手册以便得知驱动需要用到的寄存器地址

   注意：

   1. 此处寄存器是指二级外设内部的寄存器，每个寄存器在芯片手册里有个对应编号（也被称为地址），但不是内存地址，特别提醒此寄存器不是SOC芯片内部参与内存统一编址的寄存器，更不是ARM核-CPU的寄存器
   2. 通过调用i2c_tranfer函数完成与相应寄存器的数据交互

4. 参照字符驱动完成其余代码编写

5. 创建对应的i2c_client对象

   linux-3.14\Documentation\i2c\instantiating-devices

   匹配方式：

   1. 名称匹配

   2. 设备树匹配

   3. ACPI匹配

      Advanced Configuration and Power Management Interface 高级配置和电源管理接口

      PC机平台采用的一种硬件配置接口

i2c二级外设驱动框架：

//其它struct file_operations函数实现原理同硬编驱动static int mpu6050_probe(struct i2c_client *pclt,const struct i2c_device_id *pid)
{//做硬编驱动模块入口函数的活
}static int mpu6050_remove(struct i2c_client *pclt)
{//做硬编驱动模块出口函数的活
}/*名称匹配时定义struct i2c_device_id数组*/
static struct i2c_device_id mpu6050_ids = 
{{"mpu6050",0},//.....{}
};/*设备树匹配时定义struct of_device_id数组*/
static struct of_device_id mpu6050_dts =
{{.compatible = "invensense,mpu6050"},//....{}
};/*通过定义struct i2c_driver类型的全局变量来创建i2c_driver对象，同时对其主要成员进行初始化*/
struct i2c_driver mpu6050_driver = 
{.driver = {.name = "mpu6050",.owner = THIS_MODULE,.of_match_table = mpu6050_dts,},.probe = mpu6050_probe,.remove = mpu6050_remove,.id_table = mpu6050_ids,
};/*以下其实是个宏，展开后相当于实现了模块入口函数和模块出口函数*/
module_i2c_driver(mpu6050_driver);MODULE_LICENSE("GPL");

七、I2C总线二级外设驱动开发之名称匹配

这种匹配方式需要自己创建i2c_client对象

创建i2c_client对象有三种方式：

1. i2c_register_board_info

1. 当开发板上电内核跑起来的时候，肯定是架构相关的程序首先运行，也就是mach-xxx.c
2. mach-xxx.c文件里首先会定义i2c_board_info的结构体数组，在mach-xxx.c的初始化函数里调用 i2c_register_board_info函数把i2c_board_inifo链接进内核的i2c_board_list链表当中去
3. 在驱动i2c目录下和开发板板对应的驱动文件i2c-xxx.c里，创建i2c_adapter对象
4. 这种方式严重依赖平台，缺乏灵活性，基本会被遗弃

2. i2c_new_device：明确二级外设地址的情况下可用

i2c二级外设client框架：

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>static struct i2c_board_info mpu6050_info = 
{I2C_BOARD_INFO("mpu6050",二级外设地址)   
};static struct i2c_client *mpu6050_client;
static int __init mpu6050_dev_init(void)
{struct i2c_adapter *padp = NULL;padp = i2c_get_adapter(i2c通道编号);mpu6050_client = i2c_new_device(padp,&mpu6050_info);i2c_put_adapter(padp);return 0;
}
module_init(mpu6050_dev_init);static void __exit mpu6050_dev_exit(void)
{i2c_unregister_device(mpu6050_client);
}
module_exit(mpu6050_dev_exit);
MODULE_LICENSE("GPL");

完整代码

mpu6050.h

#ifndef MPU_6050_H
#define MPU_6050_Hstruct accel_data
{unsigned short x;unsigned short y;unsigned short z;
};
struct gyro_data
{unsigned short x;unsigned short y;unsigned short z;
};union mpu6050_data
{struct accel_data accel;struct gyro_data gyro;unsigned short temp;
};#define MPU6050_MAGIC 'K'#define GET_ACCEL _IOR(MPU6050_MAGIC,0,union mpu6050_data)
#define GET_GYRO _IOR(MPU6050_MAGIC,1,union mpu6050_data)
#define GET_TEMP _IOR(MPU6050_MAGIC,2,union mpu6050_data)#endif

mpu6050_client.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>static struct i2c_board_info mpu6050_info = 
{I2C_BOARD_INFO("mpu6050",0x68)
};static struct i2c_client *gpmpu6050_client = NULL;static int __init mpu6050_client_init(void)
{struct i2c_adapter *padp = NULL;padp = i2c_get_adapter(5);gpmpu6050_client = i2c_new_device(padp,&mpu6050_info);i2c_put_adapter(padp);return 0;
}static void  mpu6050_client_exit(void)
{i2c_unregister_device(gpmpu6050_client);
}module_init(mpu6050_client_init);
module_exit(mpu6050_client_exit);
MODULE_LICENSE("GPL");

mpu6050_drv.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/i2c.h>
#include <linux/cdev.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>#include "mpu6050.h"/****************MPU6050内部寄存器地址****************/#define	SMPLRT_DIV		0x19	//陀螺仪采样率，典型值：0x07(125Hz)
#define	CONFIG			0x1A	//低通滤波频率，典型值：0x06(5Hz)
#define	GYRO_CONFIG		0x1B	//陀螺仪自检及测量范围，典型值：0x18(不自检，2000deg/s)
#define	ACCEL_CONFIG	0x1C	//加速计自检、测量范围及高通滤波频率，典型值：0x18(不自检，2G，5Hz)
#define	ACCEL_XOUT_H	0x3B
#define	ACCEL_XOUT_L	0x3C
#define	ACCEL_YOUT_H	0x3D
#define	ACCEL_YOUT_L	0x3E
#define	ACCEL_ZOUT_H	0x3F
#define	ACCEL_ZOUT_L	0x40
#define	TEMP_OUT_H		0x41
#define	TEMP_OUT_L		0x42
#define	GYRO_XOUT_H		0x43
#define	GYRO_XOUT_L		0x44
#define	GYRO_YOUT_H		0x45
#define	GYRO_YOUT_L		0x46
#define	GYRO_ZOUT_H		0x47
#define	GYRO_ZOUT_L		0x48
#define	PWR_MGMT_1		0x6B	//电源管理，典型值：0x00(正常启用)
#define	WHO_AM_I		0x75	//IIC地址寄存器(默认数值0x68，只读)
#define	SlaveAddress	0x68	//MPU6050-I2C地址#define PWR_MGMT_1  0x6Bint major = 11;
int minor = 0;
int mpu6050_num  = 1;struct mpu6050_dev
{struct cdev mydev;struct i2c_client *pclt;};struct mpu6050_dev *pgmydev = NULL;int mpu6050_read_byte(struct i2c_client *pclt,unsigned char reg)
{int ret = 0;char txbuf[1] = {reg};char rxbuf[1] = {0};struct i2c_msg msg[2] = {{pclt->addr,0,1,txbuf},{pclt->addr,I2C_M_RD,1,rxbuf}};ret = i2c_transfer(pclt->adapter,msg,ARRAY_SIZE(msg));if(ret < 0){printk("ret = %d,in mpu6050_read_byte\n",ret);return ret;}return rxbuf[0];
}int mpu6050_write_byte(struct i2c_client *pclt,unsigned char reg,unsigned char val)
{int ret = 0;char txbuf[2] = {reg,val};struct i2c_msg msg[1] = {{pclt->addr,0,2,txbuf},};ret = i2c_transfer(pclt->adapter,msg,ARRAY_SIZE(msg));if(ret < 0){printk("ret = %d,in mpu6050_write_byte\n",ret);return ret;}return 0;
}int mpu6050_open(struct inode *pnode,struct file *pfile)
{pfile->private_data =(void *) (container_of(pnode->i_cdev,struct mpu6050_dev,mydev));return 0;
}int mpu6050_close(struct inode *pnode,struct file *pfile)
{return 0;
}long mpu6050_ioctl(struct file *pfile,unsigned int cmd,unsigned long arg)
{struct mpu6050_dev *pmydev = (struct mpu6050_dev *)pfile->private_data;union mpu6050_data data;switch(cmd){case GET_ACCEL:data.accel.x = mpu6050_read_byte(pmydev->pclt,ACCEL_XOUT_L);data.accel.x = mpu6050_read_byte(pmydev->pclt,ACCEL_XOUT_H) << 8;data.accel.y = mpu6050_read_byte(pmydev->pclt,ACCEL_YOUT_L);data.accel.y = mpu6050_read_byte(pmydev->pclt,ACCEL_YOUT_H) << 8;data.accel.z = mpu6050_read_byte(pmydev->pclt,ACCEL_ZOUT_L);data.accel.z = mpu6050_read_byte(pmydev->pclt,ACCEL_ZOUT_H) << 8;break;case GET_GYRO:data.gyro.x = mpu6050_read_byte(pmydev->pclt,GYRO_XOUT_L);data.gyro.x = mpu6050_read_byte(pmydev->pclt,GYRO_XOUT_H) << 8;data.gyro.y = mpu6050_read_byte(pmydev->pclt,GYRO_YOUT_L);data.gyro.y = mpu6050_read_byte(pmydev->pclt,GYRO_YOUT_H) << 8;data.gyro.z = mpu6050_read_byte(pmydev->pclt,GYRO_ZOUT_L);data.gyro.z = mpu6050_read_byte(pmydev->pclt,GYRO_ZOUT_H) << 8;break;case GET_TEMP:data.temp = mpu6050_read_byte(pmydev->pclt,TEMP_OUT_L);data.temp = mpu6050_read_byte(pmydev->pclt,TEMP_OUT_H) << 8;break;default:return -EINVAL;}if(copy_to_user((void *)arg,&data,sizeof(data))){return -EFAULT;}return sizeof(data);
}void init_mpu6050(struct i2c_client *pclt)
{mpu6050_write_byte(pclt,PWR_MGMT_1,0x00);mpu6050_write_byte(pclt,SMPLRT_DIV,0x07);mpu6050_write_byte(pclt,CONFIG,0x06);mpu6050_write_byte(pclt,GYRO_CONFIG,0xF8);mpu6050_write_byte(pclt,ACCEL_CONFIG,0x19);
}struct file_operations myops = {.owner = THIS_MODULE,.open = mpu6050_open,.release = mpu6050_close,.unlocked_ioctl = mpu6050_ioctl,
};static int mpu6050_probe(struct i2c_client *pclt,const struct i2c_device_id *pid)
{int ret = 0;dev_t devno = MKDEV(major,minor);/*申请设备号*/ret = register_chrdev_region(devno,mpu6050_num,"mpu6050");if(ret){ret = alloc_chrdev_region(&devno,minor,mpu6050_num,"mpu6050");if(ret){printk("get devno failed\n");return -1;}major = MAJOR(devno);//容易遗漏，注意}pgmydev = (struct mpu6050_dev *)kmalloc(sizeof(struct mpu6050_dev),GFP_KERNEL);if(NULL == pgmydev){unregister_chrdev_region(devno,mpu6050_num);printk("kmalloc failed\n");return -1;}memset(pgmydev,0,sizeof(struct mpu6050_dev));pgmydev->pclt = pclt;/*给struct cdev对象指定操作函数集*/	cdev_init(&pgmydev->mydev,&myops);/*将struct cdev对象添加到内核对应的数据结构里*/pgmydev->mydev.owner = THIS_MODULE;cdev_add(&pgmydev->mydev,devno,mpu6050_num);init_mpu6050(pgmydev->pclt);return 0;
}static int mpu6050_remove(struct i2c_client *pclt)
{dev_t devno = MKDEV(major,minor);cdev_del(&pgmydev->mydev);unregister_chrdev_region(devno,mpu6050_num);kfree(pgmydev);pgmydev = NULL;return 0;
}struct i2c_device_id mpu6050_ids[] = 
{{"mpu6050",0},{}
};struct i2c_driver mpu6050_driver = 
{.driver = {.name = "mpu6050",.owner = THIS_MODULE,},.probe = mpu6050_probe,.remove = mpu6050_remove,.id_table = mpu6050_ids,
};#if 0int __init mpu6050_driver_init(void){i2c_add_driver(&mpu6050_driver);}void __exit mpu6050_driver_exit(void){i2c_del_driver(&mpu6050_driver);}module_init(mpu6050_driver_init);module_exit(mpu6050_driver_exit);
#elsemodule_i2c_driver(mpu6050_driver);
#endifMODULE_LICENSE("GPL");

testapp.c

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>#include <stdio.h>#include "mpu6050.h"int main(int argc,char *argv[])
{int fd = -1;union mpu6050_data data;if(argc < 2){printf("The argument is too few\n");return 1;}fd = open(argv[1],O_RDONLY);if(fd < 0){printf("open %s failed \n",argv[1]);return 2;}while(1){sleep(2);ioctl(fd,GET_ACCEL,&data);printf("Accel-x=0x%x\n",data.accel.x);printf("Accel-y=0x%x\n",data.accel.y);printf("Accel-z=0x%x\n",data.accel.z);ioctl(fd,GET_GYRO,&data);printf("Gyro-x=0x%x\n",data.gyro.x);printf("Gyro-y=0x%x\n",data.gyro.y);printf("Gyro-z=0x%x\n",data.gyro.z);ioctl(fd,GET_TEMP,&data);printf("Temp=0x%x\n",data.temp);printf("\n");}close(fd);fd = -1;return 0;
}

输出结果：

3. i2c_new_probed_device：不明确二级外设地址

i2c二级外设client框架：不明确二级外设地址，但是知道是可能几个值之一的情况下可用

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>static const unsigned short addr_list[] = 
{0x68,//.....I2C_CLIENT_END
};static struct i2c_client *mpu6050_client;
static int __init mpu6050_dev_init(void)
{struct i2c_adapter *padp = NULL;struct i2c_board_info mpu6050_info = {""};strcpy(mpu6050_info.type,"mpu6050");padp = i2c_get_adapter(i2c通道编号);mpu6050_client = i2c_new_probed_device(padp,&mpu6050_info,addr_list,NULL);i2c_put_adapter(padp);if(mpu6050_client != NULL){return 0;}else{return -ENODEV;}
}
module_init(mpu6050_dev_init);static void __exit mpu6050_dev_exit(void)
{i2c_unregister_device(mpu6050_client);
}
module_exit(mpu6050_dev_exit);
MODULE_LICENSE("GPL");

完整代码

mpu6050.h

#ifndef MPU_6050_H
#define MPU_6050_Hstruct accel_data
{unsigned short x;unsigned short y;unsigned short z;
};
struct gyro_data
{unsigned short x;unsigned short y;unsigned short z;
};union mpu6050_data
{struct accel_data accel;struct gyro_data gyro;unsigned short temp;
};#define MPU6050_MAGIC 'K'#define GET_ACCEL _IOR(MPU6050_MAGIC,0,union mpu6050_data)
#define GET_GYRO _IOR(MPU6050_MAGIC,1,union mpu6050_data)
#define GET_TEMP _IOR(MPU6050_MAGIC,2,union mpu6050_data)#endif

mpu6050_client_probed.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>static unsigned short mpu6050_addr_list[] = 
{0x68,0x69,I2C_CLIENT_END
};static struct i2c_client *gpmpu6050_client = NULL;static int __init mpu6050_client_init(void)
{struct i2c_adapter *padp = NULL;struct i2c_board_info mpu6050_info = {""};strcpy(mpu6050_info.type,"mpu6050");padp = i2c_get_adapter(5);gpmpu6050_client = i2c_new_probed_device(padp,&mpu6050_info,mpu6050_addr_list,NULL);i2c_put_adapter(padp);if(gpmpu6050_client != NULL){return 0;}else{return -ENODEV;}
}static void  mpu6050_client_exit(void)
{i2c_unregister_device(gpmpu6050_client);
}module_init(mpu6050_client_init);
module_exit(mpu6050_client_exit);
MODULE_LICENSE("GPL");

mpu6050_drv.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/i2c.h>
#include <linux/cdev.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>#include "mpu6050.h"#define SMPLRT_DIV 0x19
#define CONFIG 0x1A
#define GYRO_CONFIG 0x1B
#define ACCEL_CONFIG 0x1C#define ACCEL_XOUT_H 0x3B
#define ACCEL_XOUT_L 0x3C
#define ACCEL_YOUT_H 0x3D
#define ACCEL_YOUT_L 0x3E
#define ACCEL_ZOUT_H 0x3F
#define ACCEL_ZOUT_L 0x40
#define TEMP_OUT_H 0x41
#define TEMP_OUT_L 0x42
#define GYRO_XOUT_H 0x43
#define GYRO_XOUT_L 0x44
#define GYRO_YOUT_H 0x45
#define GYRO_YOUT_L 0x46
#define GYRO_ZOUT_H 0x47
#define GYRO_ZOUT_L 0x48#define PWR_MGMT_1  0x6Bint major = 11;
int minor = 0;
int mpu6050_num  = 1;struct mpu6050_dev
{struct cdev mydev;struct i2c_client *pclt;};struct mpu6050_dev *pgmydev = NULL;int mpu6050_read_byte(struct i2c_client *pclt,unsigned char reg)
{int ret = 0;char txbuf[1] = {reg};char rxbuf[1] = {0};struct i2c_msg msg[2] = {{pclt->addr,0,1,txbuf},{pclt->addr,I2C_M_RD,1,rxbuf}};ret = i2c_transfer(pclt->adapter,msg,ARRAY_SIZE(msg));if(ret < 0){printk("ret = %d,in mpu6050_read_byte\n",ret);return ret;}return rxbuf[0];
}int mpu6050_write_byte(struct i2c_client *pclt,unsigned char reg,unsigned char val)
{int ret = 0;char txbuf[2] = {reg,val};struct i2c_msg msg[1] = {{pclt->addr,0,2,txbuf},};ret = i2c_transfer(pclt->adapter,msg,ARRAY_SIZE(msg));if(ret < 0){printk("ret = %d,in mpu6050_write_byte\n",ret);return ret;}return 0;
}int mpu6050_open(struct inode *pnode,struct file *pfile)
{pfile->private_data =(void *) (container_of(pnode->i_cdev,struct mpu6050_dev,mydev));return 0;
}int mpu6050_close(struct inode *pnode,struct file *pfile)
{return 0;
}long mpu6050_ioctl(struct file *pfile,unsigned int cmd,unsigned long arg)
{struct mpu6050_dev *pmydev = (struct mpu6050_dev *)pfile->private_data;union mpu6050_data data;switch(cmd){case GET_ACCEL:data.accel.x = mpu6050_read_byte(pmydev->pclt,ACCEL_XOUT_L);data.accel.x = mpu6050_read_byte(pmydev->pclt,ACCEL_XOUT_H) << 8;data.accel.y = mpu6050_read_byte(pmydev->pclt,ACCEL_YOUT_L);data.accel.y = mpu6050_read_byte(pmydev->pclt,ACCEL_YOUT_H) << 8;data.accel.z = mpu6050_read_byte(pmydev->pclt,ACCEL_ZOUT_L);data.accel.z = mpu6050_read_byte(pmydev->pclt,ACCEL_ZOUT_H) << 8;break;case GET_GYRO:data.gyro.x = mpu6050_read_byte(pmydev->pclt,GYRO_XOUT_L);data.gyro.x = mpu6050_read_byte(pmydev->pclt,GYRO_XOUT_H) << 8;data.gyro.y = mpu6050_read_byte(pmydev->pclt,GYRO_YOUT_L);data.gyro.y = mpu6050_read_byte(pmydev->pclt,GYRO_YOUT_H) << 8;data.gyro.z = mpu6050_read_byte(pmydev->pclt,GYRO_ZOUT_L);data.gyro.z = mpu6050_read_byte(pmydev->pclt,GYRO_ZOUT_H) << 8;break;case GET_TEMP:data.temp = mpu6050_read_byte(pmydev->pclt,TEMP_OUT_L);data.temp = mpu6050_read_byte(pmydev->pclt,TEMP_OUT_H) << 8;break;default:return -EINVAL;}if(copy_to_user((void *)arg,&data,sizeof(data))){return -EFAULT;}return sizeof(data);
}void init_mpu6050(struct i2c_client *pclt)
{mpu6050_write_byte(pclt,PWR_MGMT_1,0x00);mpu6050_write_byte(pclt,SMPLRT_DIV,0x07);mpu6050_write_byte(pclt,CONFIG,0x06);mpu6050_write_byte(pclt,GYRO_CONFIG,0xF8);mpu6050_write_byte(pclt,ACCEL_CONFIG,0x19);
}struct file_operations myops = {.owner = THIS_MODULE,.open = mpu6050_open,.release = mpu6050_close,.unlocked_ioctl = mpu6050_ioctl,
};static int mpu6050_probe(struct i2c_client *pclt,const struct i2c_device_id *pid)
{int ret = 0;dev_t devno = MKDEV(major,minor);/*申请设备号*/ret = register_chrdev_region(devno,mpu6050_num,"mpu6050");if(ret){ret = alloc_chrdev_region(&devno,minor,mpu6050_num,"mpu6050");if(ret){printk("get devno failed\n");return -1;}major = MAJOR(devno);//容易遗漏，注意}pgmydev = (struct mpu6050_dev *)kmalloc(sizeof(struct mpu6050_dev),GFP_KERNEL);if(NULL == pgmydev){unregister_chrdev_region(devno,mpu6050_num);printk("kmalloc failed\n");return -1;}memset(pgmydev,0,sizeof(struct mpu6050_dev));pgmydev->pclt = pclt;/*给struct cdev对象指定操作函数集*/	cdev_init(&pgmydev->mydev,&myops);/*将struct cdev对象添加到内核对应的数据结构里*/pgmydev->mydev.owner = THIS_MODULE;cdev_add(&pgmydev->mydev,devno,mpu6050_num);init_mpu6050(pgmydev->pclt);return 0;
}static int mpu6050_remove(struct i2c_client *pclt)
{dev_t devno = MKDEV(major,minor);cdev_del(&pgmydev->mydev);unregister_chrdev_region(devno,mpu6050_num);kfree(pgmydev);pgmydev = NULL;return 0;
}struct i2c_device_id mpu6050_ids[] = 
{{"mpu6050",0},{}
};struct i2c_driver mpu6050_driver = 
{.driver = {.name = "mpu6050",.owner = THIS_MODULE,},.probe = mpu6050_probe,.remove = mpu6050_remove,.id_table = mpu6050_ids,
};#if 0int __init mpu6050_driver_init(void){i2c_add_driver(&mpu6050_driver);}void __exit mpu6050_driver_exit(void){i2c_del_driver(&mpu6050_driver);}module_init(mpu6050_driver_init);module_exit(mpu6050_driver_exit);
#elsemodule_i2c_driver(mpu6050_driver);
#endifMODULE_LICENSE("GPL");

testapp.c

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>#include <stdio.h>#include "mpu6050.h"int main(int argc,char *argv[])
{int fd = -1;union mpu6050_data data;if(argc < 2){printf("The argument is too few\n");return 1;}fd = open(argv[1],O_RDONLY);if(fd < 0){printf("open %s failed \n",argv[1]);return 2;}while(1){sleep(2);ioctl(fd,GET_ACCEL,&data);printf("Accel-x=0x%x\n",data.accel.x);printf("Accel-y=0x%x\n",data.accel.y);printf("Accel-z=0x%x\n",data.accel.z);ioctl(fd,GET_GYRO,&data);printf("Gyro-x=0x%x\n",data.gyro.x);printf("Gyro-y=0x%x\n",data.gyro.y);printf("Gyro-z=0x%x\n",data.gyro.z);ioctl(fd,GET_TEMP,&data);printf("Temp=0x%x\n",data.temp);printf("\n");}close(fd);fd = -1;return 0;
}

输出结果：

八、I2C总线二级外设驱动开发之设备树匹配

完整代码

mpu6050.h

#ifndef MPU_6050_H
#define MPU_6050_Hstruct accel_data
{unsigned short x;unsigned short y;unsigned short z;
};
struct gyro_data
{unsigned short x;unsigned short y;unsigned short z;
};union mpu6050_data
{struct accel_data accel;struct gyro_data gyro;unsigned short temp;
};#define MPU6050_MAGIC 'K'#define GET_ACCEL _IOR(MPU6050_MAGIC,0,union mpu6050_data)
#define GET_GYRO _IOR(MPU6050_MAGIC,1,union mpu6050_data)
#define GET_TEMP _IOR(MPU6050_MAGIC,2,union mpu6050_data)#endif

mpu6050_drv.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/i2c.h>
#include <linux/cdev.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>#include "mpu6050.h"#define SMPLRT_DIV 0x19
#define CONFIG 0x1A
#define GYRO_CONFIG 0x1B
#define ACCEL_CONFIG 0x1C#define ACCEL_XOUT_H 0x3B
#define ACCEL_XOUT_L 0x3C
#define ACCEL_YOUT_H 0x3D
#define ACCEL_YOUT_L 0x3E
#define ACCEL_ZOUT_H 0x3F
#define ACCEL_ZOUT_L 0x40
#define TEMP_OUT_H 0x41
#define TEMP_OUT_L 0x42
#define GYRO_XOUT_H 0x43
#define GYRO_XOUT_L 0x44
#define GYRO_YOUT_H 0x45
#define GYRO_YOUT_L 0x46
#define GYRO_ZOUT_H 0x47
#define GYRO_ZOUT_L 0x48#define PWR_MGMT_1  0x6Bint major = 11;
int minor = 0;
int mpu6050_num  = 1;struct mpu6050_dev
{struct cdev mydev;struct i2c_client *pclt;};struct mpu6050_dev *pgmydev = NULL;int mpu6050_read_byte(struct i2c_client *pclt,unsigned char reg)
{int ret = 0;char txbuf[1] = {reg};char rxbuf[1] = {0};struct i2c_msg msg[2] = {{pclt->addr,0,1,txbuf},{pclt->addr,I2C_M_RD,1,rxbuf}};ret = i2c_transfer(pclt->adapter,msg,ARRAY_SIZE(msg));if(ret < 0){printk("ret = %d,in mpu6050_read_byte\n",ret);return ret;}return rxbuf[0];
}int mpu6050_write_byte(struct i2c_client *pclt,unsigned char reg,unsigned char val)
{int ret = 0;char txbuf[2] = {reg,val};struct i2c_msg msg[1] = {{pclt->addr,0,2,txbuf},};ret = i2c_transfer(pclt->adapter,msg,ARRAY_SIZE(msg));if(ret < 0){printk("ret = %d,in mpu6050_write_byte\n",ret);return ret;}return 0;
}int mpu6050_open(struct inode *pnode,struct file *pfile)
{pfile->private_data =(void *) (container_of(pnode->i_cdev,struct mpu6050_dev,mydev));return 0;
}int mpu6050_close(struct inode *pnode,struct file *pfile)
{return 0;
}long mpu6050_ioctl(struct file *pfile,unsigned int cmd,unsigned long arg)
{struct mpu6050_dev *pmydev = (struct mpu6050_dev *)pfile->private_data;union mpu6050_data data;switch(cmd){case GET_ACCEL:data.accel.x = mpu6050_read_byte(pmydev->pclt,ACCEL_XOUT_L);data.accel.x = mpu6050_read_byte(pmydev->pclt,ACCEL_XOUT_H) << 8;data.accel.y = mpu6050_read_byte(pmydev->pclt,ACCEL_YOUT_L);data.accel.y = mpu6050_read_byte(pmydev->pclt,ACCEL_YOUT_H) << 8;data.accel.z = mpu6050_read_byte(pmydev->pclt,ACCEL_ZOUT_L);data.accel.z = mpu6050_read_byte(pmydev->pclt,ACCEL_ZOUT_H) << 8;break;case GET_GYRO:data.gyro.x = mpu6050_read_byte(pmydev->pclt,GYRO_XOUT_L);data.gyro.x = mpu6050_read_byte(pmydev->pclt,GYRO_XOUT_H) << 8;data.gyro.y = mpu6050_read_byte(pmydev->pclt,GYRO_YOUT_L);data.gyro.y = mpu6050_read_byte(pmydev->pclt,GYRO_YOUT_H) << 8;data.gyro.z = mpu6050_read_byte(pmydev->pclt,GYRO_ZOUT_L);data.gyro.z = mpu6050_read_byte(pmydev->pclt,GYRO_ZOUT_H) << 8;break;case GET_TEMP:data.temp = mpu6050_read_byte(pmydev->pclt,TEMP_OUT_L);data.temp = mpu6050_read_byte(pmydev->pclt,TEMP_OUT_H) << 8;break;default:return -EINVAL;}if(copy_to_user((void *)arg,&data,sizeof(data))){return -EFAULT;}return sizeof(data);
}void init_mpu6050(struct i2c_client *pclt)
{mpu6050_write_byte(pclt,PWR_MGMT_1,0x00);mpu6050_write_byte(pclt,SMPLRT_DIV,0x07);mpu6050_write_byte(pclt,CONFIG,0x06);mpu6050_write_byte(pclt,GYRO_CONFIG,0xF8);mpu6050_write_byte(pclt,ACCEL_CONFIG,0x19);
}struct file_operations myops = {.owner = THIS_MODULE,.open = mpu6050_open,.release = mpu6050_close,.unlocked_ioctl = mpu6050_ioctl,
};static int mpu6050_probe(struct i2c_client *pclt,const struct i2c_device_id *pid)
{int ret = 0;dev_t devno = MKDEV(major,minor);/*申请设备号*/ret = register_chrdev_region(devno,mpu6050_num,"mpu6050");if(ret){ret = alloc_chrdev_region(&devno,minor,mpu6050_num,"mpu6050");if(ret){printk("get devno failed\n");return -1;}major = MAJOR(devno);//容易遗漏，注意}pgmydev = (struct mpu6050_dev *)kmalloc(sizeof(struct mpu6050_dev),GFP_KERNEL);if(NULL == pgmydev){unregister_chrdev_region(devno,mpu6050_num);printk("kmalloc failed\n");return -1;}memset(pgmydev,0,sizeof(struct mpu6050_dev));pgmydev->pclt = pclt;/*给struct cdev对象指定操作函数集*/	cdev_init(&pgmydev->mydev,&myops);/*将struct cdev对象添加到内核对应的数据结构里*/pgmydev->mydev.owner = THIS_MODULE;cdev_add(&pgmydev->mydev,devno,mpu6050_num);init_mpu6050(pgmydev->pclt);return 0;
}static int mpu6050_remove(struct i2c_client *pclt)
{dev_t devno = MKDEV(major,minor);cdev_del(&pgmydev->mydev);unregister_chrdev_region(devno,mpu6050_num);kfree(pgmydev);pgmydev = NULL;return 0;
}struct of_device_id mpu6050_dt[] = 
{{.compatible = "invensense,mpu6050"},{}
};struct i2c_device_id mpu6050_ids[] = 
{{"mpu6050",0},{}
};struct i2c_driver mpu6050_driver = 
{.driver = {.name = "mpu6050",.owner = THIS_MODULE,.of_match_table = mpu6050_dt,},.probe = mpu6050_probe,.remove = mpu6050_remove,.id_table = mpu6050_ids,
};#if 0
int __init mpu6050_driver_init(void)
{i2c_add_driver(&mpu6050_driver);
}void __exit mpu6050_driver_exit(void)
{i2c_del_driver(&mpu6050_driver);
}
module_init(mpu6050_driver_init);
module_exit(mpu6050_driver_exit);
#else
module_i2c_driver(mpu6050_driver);
#endifMODULE_LICENSE("GPL");

testapp.c

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>#include <stdio.h>#include "mpu6050.h"int main(int argc,char *argv[])
{int fd = -1;union mpu6050_data data;if(argc < 2){printf("The argument is too few\n");return 1;}fd = open(argv[1],O_RDONLY);if(fd < 0){printf("open %s failed \n",argv[1]);return 2;}while(1){sleep(2);ioctl(fd,GET_ACCEL,&data);printf("Accel-x=0x%x\n",data.accel.x);printf("Accel-y=0x%x\n",data.accel.y);printf("Accel-z=0x%x\n",data.accel.z);ioctl(fd,GET_GYRO,&data);printf("Gyro-x=0x%x\n",data.gyro.x);printf("Gyro-y=0x%x\n",data.gyro.y);printf("Gyro-z=0x%x\n",data.gyro.z);ioctl(fd,GET_TEMP,&data);printf("Temp=0x%x\n",data.temp);printf("\n");}close(fd);fd = -1;return 0;
}

输出结果：