目录
1）向I2C设备中读出或者写入一个字节(8位)/两个字节(16位)的数据
[3）i2c_master_send （）和 i2c_master_recv（）](#3）i2c_master_send （）和 i2c_master_recv（）)
AP3216C不做具体的介绍，本文主要介绍LInux是如何驱动IIC设备的
传感器具体的介绍可以参考：详解AP3216C（三合一sensor： 光照、距离、照射强度）驱动开发-CSDN博客
1.编写设备树
首先设置 I2C1 引脚的复用功能和电气属性，找到 pinctrl_i2c1 节点：
已经设置好了，不需要编写
2.添加新的IIC设备
找到IIC子节点补充描述
cpp
ap3216c@1e{
compatible = "my_ap3216c";
reg = <0x1e>;
};切换到内核目录下，重新编译(make dtbs)即可，将编译好的dtb文件移动到开发板的boot目录下面即可。重新启动开发板即可。
3.编写AP3216C的驱动程序如下
cpp
#include <linux/init.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/uaccess.h>
#include <linux/mod_devicetable.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/delay.h>
static int major;
static struct class *ap3216c_class;
static struct i2c_client *ap3216c_client;
static int ap3216c_open(struct inode *inode, struct file *filp) {
/*reset: write 0x4 to reg 0*/
i2c_smbus_write_byte_data(ap3216c_client, 0, 0x4);
/*delay for reset*/
mdelay(15);
/*enable:write 0x3 to reg 0*/
i2c_smbus_write_byte_data(ap3216c_client, 0, 0x3);
return 0;
}
static ssize_t ap3216c_read(struct file *filp, char __user *buf, size_t size,
loff_t *offset) {
int var, err;
char data[6];
if (size != 6) {
return -EINVAL;
}
// read IR
var = i2c_smbus_read_word_data(ap3216c_client, 0xa);
//将读取到的16位数据var拆分为两个8位的字节，并分别存储到data[0]与data[1]中
//第一个代码，将var右移8位，取出高8位，(8-15),然后与0xff进行按位与操作，确保结果是一个8位的值
//第二个代码，取出var的低8位（0-7）,并且存储到data[1]中。
data[0] = (var >> 8) & 0xff;
data[1] = var & 0xff;
// read light
var = i2c_smbus_read_word_data(ap3216c_client, 0xc);
data[2] = (var >> 8) & 0xff;
data[3] = var & 0xff;
// read distance
var = i2c_smbus_read_word_data(ap3216c_client, 0xe);
data[4] = (var >> 8) & 0xff;
data[5] = var & 0xff;
err = copy_to_user(buf, data, size);
return 0;
}
static struct file_operations ap3216c_fops = {
.owner = THIS_MODULE,
.open = ap3216c_open,
.read = ap3216c_read,
};
// 用于和设备书进行匹配
static const struct of_device_id ap3216c_dt_match[] = {
{
.compatible = "my_ap3216c",
},
{},
};
static const struct i2c_device_id ap3216c_i2c_id[] = {
{
"ap3216c",
},
{}
};
static int ap3216c_i2c_probe(struct i2c_client* client,const struct i2c_device_id *i2c_id){
struct device *result;
ap3216c_client = client;
printk("====%s====\n", __FUNCTION__);
/*register chrdev*/
major = register_chrdev(0, "ap3216c", &ap3216c_fops);
ap3216c_class = class_create(THIS_MODULE, "ap3216c_class");
if (IS_ERR(ap3216c_class)) {
printk("ap3216c class_create failed!\n");
unregister_chrdev(major, "ap3216c");
return PTR_ERR(ap3216c_class);
}
result = device_create(ap3216c_class, NULL, MKDEV(major, 0), NULL, "ap3216c");
if (IS_ERR(result)) {
printk("ap3216c device_create failed\n");
class_destroy(ap3216c_class);
unregister_chrdev(major, "ap3216c");
return -EINVAL;
}
dev_info(&client->dev, "=====ap3216c initialized successfully====\n");
return 0;
}
static int ap3216c_i2c_remove(struct i2c_client *client) {
printk("======%s=====\n", __FUNCTION__);
device_destroy(ap3216c_class, MKDEV(major, 0));
class_destroy(ap3216c_class);
unregister_chrdev(major, "ap3216c");
return 0;
}
static struct i2c_driver ap3216c_i2c_driver = {
.driver =
{
.owner = THIS_MODULE,
.name = "ap3216c",
.of_match_table = ap3216c_dt_match,
},
.probe = ap3216c_i2c_probe,
.remove = ap3216c_i2c_remove,
.id_table = ap3216c_i2c_id,
};
static int __init ap3216c_i2c_init(void) {
int ret;
printk("====%s====\n", __FUNCTION__);
ret = i2c_add_driver(&ap3216c_i2c_driver);
if (ret != 0) {
pr_err("Failed to register ap3216c I2C driver: %d \n", ret);
}
return 0;
}
static void __exit ap3216c_i2c_exit(void) {
printk("====%s====\n", __FUNCTION__);
i2c_del_driver(&ap3216c_i2c_driver);
}
module_init(ap3216c_i2c_init);
module_exit(ap3216c_i2c_exit);
MODULE_LICENSE("GPL");4.对IIC驱动函数详细解读
1.SMBUS
SMBUS常用的函数集有：
cpp
s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command);
s32 i2c_smbus_write_byte_data(const struct i2c_client *client,u8 command, u8 value);
s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command);
s32 i2c_smbus_write_word_data(const struct i2c_client *client,u8 command, u16 value);
s32 i2c_smbus_read_block_data(const struct i2c_client *client,u8 command, u8 *values);
s32 i2c_smbus_write_block_data(const struct i2c_client *client,u8 command, u8 length, const u8 *values);
s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client,u8 command, u8 length, u8 *values);
s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client,u8 command, u8 length, const u8 *values);1）向I2C设备中读出或者写入一个字节(8位)/两个字节(16位)的数据
cpp
/* client:client是指i2c slave 设备,使用时有时需要初始化其i2c地址
* command :读写的寄存器地址
* value:写入的数据,为8位
*/
s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command);
s32 i2c_smbus_write_byte_data(const struct i2c_client *client,u8 command, u8 value);
s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command);
/*value:写入的数据,为16位*/
s32 i2c_smbus_write_word_data(const struct i2c_client *client,u8 command, u16 value);比如这个函数中，open函数中打开设备后做了下面的事情
cpp
/*reset: write 0x4 to reg 0*/
i2c_smbus_write_byte_data(ap3216c_client, 0, 0x4);
/*enable:write 0x3 to reg 0*/
i2c_smbus_write_byte_data(ap3216c_client, 0, 0x3);在read函数中，读取
cpp
var = i2c_smbus_read_word_data(ap3216c_client, 0xa);
data[0] = (var >> 8) & 0xff;
data[1] = var & 0xff;
// read light
var = i2c_smbus_read_word_data(ap3216c_client, 0xc);
data[2] = (var >> 8) & 0xff;
data[3] = var & 0xff;
// read distance
var = i2c_smbus_read_word_data(ap3216c_client, 0xe);
data[4] = (var >> 8) & 0xff;
data[5] = var & 0xff;2）读取或者写入指定长度的值,一般使用后面两个
cpp
/* client:client是指i2c slave 设备,使用时有时需要初始化其i2c地址
* command :读写的寄存器地址
* length :读取或者写入长度
* value :写入的数据,值的类型为u8
*/
s32 i2c_smbus_read_block_data(const struct i2c_client *client,u8 command, u8 *values);
s32 i2c_smbus_write_block_data(const struct i2c_client *client,u8 command, u8 length, const u8 *values);
s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client,u8 command, u8 length, u8 *values);
s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client,u8 command, u8 length, const u8 *values);举例：
cpp
/* 其中client中会保存slave的I2C地址
* 0x03为寄存器地址
* write_buf是一个u8类型的数组
* 4为长度
*/
static int write_reg(struct i2c_client *client, int addr,u8* data, int len)
{
return i2c_smbus_write_i2c_block_data(client,addr,len,data);
}
void func()
{
u8 write_buf[4];
write_buf[0]=0x01;
write_buf[1]=0x02;
write_buf[2]=0x05;
write_buf[3]=0x04
write_reg(client,0x03,write_buf,4);
}
/* client中保存slave的I2C地址
* 0x20为寄存器地址
* read_buf是一个u8类型的数组
* 63为读取的长度
*/
static int read_register(struct i2c_client *client, int addr,u8* u8_val, int len)
{
return i2c_smbus_read_i2c_block_data(client,addr,len,u8_val);
}
void func()
{
u8 read_buf[80];
read_register(client, 0x20, read_buf ,80);
}3）i2c_master_send （）和 i2c_master_recv（）
在设备驱动中通常调用 i2c-core 定义的接口 i2c_master_send（） 和 i2c_master_recv（） 来发送或接收一次数据。
cpp
/*
* client:I2C从机
* buf :要发送的buf指针
* count :发送的数据长度
*/
int i2c_master_send(struct i2c_client *client,const char *buf ,int count)
{
int ret;
struct i2c_adapter *adap=client->adapter; // 获取adapter信息
struct i2c_msg msg; // 定义一个临时的数据包
msg.addr = client->addr; // 将从机地址写入数据包
msg.flags = client->flags & I2C_M_TEN; // 将从机标志并入数据包
msg.len = count; // 将此次发送的数据字节数写入数据包
msg.buf = (char *)buf; // 将发送数据指针写入数据包
ret = i2c_transfer(adap, &msg, 1); // 调用平台接口发送数据
// If everything went ok (eg： 1 msg transmitted), return bytes number transmitted, else error code.
return (ret == 1) ? count : ret; // 如果发送成功就返回字节数
}
EXPORT_SYMBOL(i2c_master_send);
/*
* client:I2C从机
* buf :要接收的buf指针
* count :发送的数据长度
*/
int i2c_master_recv(struct i2c_client *client, char *buf ,int count)
{
struct i2c_adapter *adap=client->adapter; // 获取adapter信息
struct i2c_msg msg; // 定义一个临时的数据包
int ret;
msg.addr = client->addr; // 将从机地址写入数据包
msg.flags = client->flags & I2C_M_TEN; // 将从机标志并入数据包
msg.flags |= I2C_M_RD; // 将此次通信的标志并入数据包
msg.len = count; // 将此次接收的数据字节数写入数据包
msg.buf = buf;
ret = i2c_transfer(adap, &msg, 1); // 调用平台接口接收数据
/* If everything went ok , return number of bytes transmitted, else error code. */
return (ret == 1) ? count : ret; // 如果接收成功就返回字节数
}
EXPORT_SYMBOL(i2c_master_recv); 例如：
写寄存器：
cpp
//写8位寄存器
static inline int xxx_reg_write(struct data *pdata,int index,unsigned char reg, unsigned char val)
{
unsigned char u8_buf[2] = { 0 };
unsigned int buf_len = 2;
int retry, timeout = 5;
u8_buf[0] = reg;
u8_buf[1] = val;
pdata->client->addr = ADDR + index;
for (retry = 0; retry < timeout; retry++)
{
if (i2c_master_send(pdata->client, u8_buf, buf_len) < 0)
{
printk("%s:write reg error: reg=0x%x, val=0x%x, retry = %d.\n", __func__, reg, val, retry);
msleep(5);
continue;
}
else
{
printk("%s:write reg ok: reg=0x%x, val=0x%x, retry = %d.\n", __func__, reg, val, retry);
break;
}
}
return 0;
}
//写16位寄存器
static inline int xxx_reg_write(struct data *pdata,int index,unsigned short reg, unsigned char val)
{
unsigned char u8_buf[3] = { 0 };
unsigned int buf_len = 3;
int retry, timeout = 5;
u8_buf[0] = (reg >> 8) & 0xFF;//寄存器地址高位
u8_buf[1] = reg & 0xFF; //寄存器地址低位
u8_buf[2] = val; //要发送的数据
pdata->client->addr = ADDR + index;
for (retry = 0; retry < timeout; retry++)
{
if (i2c_master_send(pdata->client, u8_buf, buf_len) < 0)
{
printk("%s:write reg error: reg=0x%x, val=0x%x, retry = %d.\n", __func__, reg, val, retry);
msleep(5);
continue;
}
else
{
printk("%s:write reg ok: reg=0x%x, val=0x%x, retry = %d.\n", __func__, reg, val, retry);
break;
}
}
return 0;
}读寄存器：
cpp
//8位读
static inline int xxx_reg_read(struct data *pdata, int index, unsigned short reg)
{
unsigned char u8_buf[2] = { 0 };
unsigned int buf_len = 1;
int retry, timeout = 5;
unsigned char u8_val = 0;
u8_buf[0] = reg;
pdata->client->addr = ADDR + index;
for (retry = 0; retry < timeout; retry++)
{
if (i2c_master_send(pdata->client, u8_buf, buf_len) < 0)
{
printk("%s:read reg error on send: reg=0x%x, retry = %d.\n", __func__, reg, retry);
msleep(5);
continue;
}
if (i2c_master_recv(pdata->client, &u8_val, 1) != 1) {
printk("%s:read reg error on recv: reg=0x%x, retry = %d.\n", __func__, reg, retry);
msleep(5);
continue;
}
break;
}
if (retry >= timeout) {
printk("%s:read reg error: reg=0x%x.\n", __func__, reg);
return -1;
}
return u8_val;
}
//16位读
static inline int xxx_reg_read(struct data *pdata, int index, unsigned short reg)
{
unsigned char u8_buf[2] = { 0 };
unsigned int buf_len = 2;
int retry, timeout = 5;
unsigned char u8_val = 0;
u8_buf[0] = (reg >> 8) & 0xFF;//寄存器地址高位
u8_buf[1] = reg & 0xFF;//寄存器地址低位
pdata->client->addr = ADDR + index;
for (retry = 0; retry < timeout; retry++)
{
if (i2c_master_send(pdata->client, u8_buf, buf_len) < 0)
{
printk("%s:read reg error on send: reg=0x%x, retry = %d.\n", __func__, reg, retry);
msleep(5);
continue;
}
if (i2c_master_recv(pdata->client, &u8_val, 1) != 1) {
printk("%s:read reg error on recv: reg=0x%x, retry = %d.\n", __func__, reg, retry);
msleep(5);
continue;
}
break;
}
if (retry >= timeout) {
printk("%s:read reg error: reg=0x%x.\n", __func__, reg);
return -1;
}
return u8_val;
}