实例介绍
【实例简介】本实例是基于linux I2C的设备驱动，能够读取温湿度传感器SHT3X_DIS的值，包括了CRC校验和温湿度值的转换，并提供了应用层调用接口
依赖于linux I2C总线驱动
【实例截图】
【核心代码】
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/uaccess.h>
#include <linux/gpio.h>
#include <linux/pwm.h>
#include <gpio.h>
#include <soc/gpio.h>
#include "humidity_temperature.h"
#define DEBUG_EN 0
#if DEBUG_EN
#define PWHERE printk("%s, %s, %d\n", __FILE__, __FUNCTION__, __LINE__);
#define PDEBUG(fmt, args...) printk(fmt, ##args);
#else
#define PWHERE ;
#define PDEBUG(fmt, args...) ;
#endif
#define DEVICE_ADDR 0x44
#define HEX_CODE_READ_STATUS_REG 0XF32D
#define HEX_CODE_SINGLE_SHOT_MOD_MEDIUM_DISABLED_READ 0X240B
#define HEX_CODE_PERIODIC_DATA_ACQUISITION_MODE_MEDIUM_1MPS 0X2126
#define HEX_CODE_READOUT_OF_MEASUREMENT_RESULTS_FOR_PERIODIC_MODE 0XE000
#define DEVICE_NAME "hum_tem"
static struct i2c_client *gclient=NULL;
#define uchar unsigned char
#define POLY 0x31
#define CRC8_INIT_VALUE 0xff
static uchar crc8(unsigned char *addr, int num)
{
int i;
uchar crc=CRC8_INIT_VALUE;
for (; num > 0; num--) /* Step through bytes in memory */
{
crc = crc ^ (*addr ); /* Fetch byte from memory, XOR into CRC top byte*/
for (i = 0; i < 8; i ) /* Prepare to rotate 8 bits */
{
if (crc & 0x80) /* b7 is set... */
crc = (crc << 1) ^ POLY; /* rotate and XOR with polynomic */
else /* b7 is clear... */
crc <<= 1; /* just rotate */
} /* Loop for 8 bits */
crc &= 0xFF; /* Ensure CRC remains 16-bit value */
} /* Loop until num=0 */
return(crc); /* Return updated CRC */
}
#define TMPERATURE_VALUED_MASK 0x01
#define HUMIDITY_VALUED_MASK 0x02
static int readout_results_for_periodic_mode(int *tmperature, int *humidity, int *data_valued) {
struct i2c_msg msg[2];
int ret;
int tmp_tmperature;
int tmp_humidity;
char buf_read[6];
char buf_write[3];
msg[0].addr = gclient->addr;
msg[0].flags = gclient->flags;
msg[0].len = 2;
msg[0].buf = (char *)buf_write;
buf_write[0] = (HEX_CODE_READOUT_OF_MEASUREMENT_RESULTS_FOR_PERIODIC_MODE>>8)&0XFF;
buf_write[1] = (HEX_CODE_READOUT_OF_MEASUREMENT_RESULTS_FOR_PERIODIC_MODE)&0XFF;
msg[1].addr = gclient->addr;
msg[1].flags = gclient->flags | I2C_M_RD;
msg[1].len = 6;
msg[1].buf = (char *)buf_read;
PWHERE;
*data_valued = 0;
ret=i2c_transfer(gclient->adapter, msg, 2);
if (ret <0) {
PDEBUG("i2c_transfer error, func:%s line:%d\n", __FUNCTION__, __LINE__);
return ret;
} else if (ret == 2) {
tmp_tmperature = buf_read[0]&0xff;
tmp_tmperature <<= 8;
tmp_tmperature |= buf_read[1]&0xff;
ret = 0;
if (buf_read[2] != crc8((uchar*)buf_read, 2) ) {
ret = -1;
PDEBUG("tmperature crc check error, func:%s line:%d\n", __FUNCTION__, __LINE__);
}
else {
*tmperature =175*tmp_tmperature/65535-45;
*data_valued |= TMPERATURE_VALUED_MASK;
PDEBUG("tmperature crc ok, tmperature:%d\n", *tmperature);
}
tmp_humidity = buf_read[3]&0xff;
tmp_humidity <<= 8;
tmp_humidity |= buf_read[4]&0xff;
if (buf_read[5] != crc8((uchar*)&buf_read[3], 2) ) {
ret = -1;
PDEBUG("humidity crc check error, func:%s line:%d\n", __FUNCTION__, __LINE__);
} else {
*humidity = 100*tmp_humidity/65535;
*data_valued |= HUMIDITY_VALUED_MASK;
PDEBUG("humidity crc ok, humidity:%d%%\n", *humidity);
}
return ret;
} else {
PDEBUG("i2c_transfer mybe error, please retry again, func:%s line:%d \n", __FUNCTION__, __LINE__);
return -1;
}
}
static int read_tmperature_and_humidity(int *tmperature, int *humidity) {
int retry_times;
char buf_write[3];
int ret ;
int part_data_valued_flag;
int part_data_valued_flag_retry=0;
retry_times=3;
retry: ret = readout_results_for_periodic_mode(tmperature, humidity, &part_data_valued_flag);
if (ret <0 && retry_times--) {
part_data_valued_flag_retry |= part_data_valued_flag;
if ( (part_data_valued_flag_retry&TMPERATURE_VALUED_MASK) && (part_data_valued_flag_retry&HUMIDITY_VALUED_MASK)) {
return 0;
}
msleep(3000);
goto retry;
} else {
if (retry_times <= 0) {
PDEBUG("read tmperature and humidity error, func:%s line:%d\n" , __FUNCTION__, __LINE__);
buf_write[0]=(HEX_CODE_PERIODIC_DATA_ACQUISITION_MODE_MEDIUM_1MPS>>8)&0XFF;
buf_write[1]=HEX_CODE_PERIODIC_DATA_ACQUISITION_MODE_MEDIUM_1MPS&0XFF;
//buf_write[2]=crc8(buf_write, 2);
ret = i2c_master_send(gclient, buf_write, 2);
if (ret <0) {
PDEBUG("set sensor in periodic data acquisition mode failed, func:%s line:%d\n" , __FUNCTION__, __LINE__);
return ret;
}
return -1;
}
return 0;
}
}
static long SHT3x_DIS_ioctl(struct file *filp,unsigned int cmd,unsigned long arg)
{
humidity_temperature_st *tmp;
int tmper=0;
int humi=0;
if (!gclient){
printk("no invalued humidity and temperature device SHT3x_DIS found\n");
return -1;
}
switch (cmd) {
case READ_TMPERATURE_AND_HUMIDITY:
if (read_tmperature_and_humidity(&tmper, &humi) <0 ) {
PDEBUG("read tmperature and humidity error, func:%s line:%d\n", __FUNCTION__, __LINE__);
return -1;
}
PDEBUG("readed tmp:%x hum:%x\n", tmper, humi);
tmp = ( humidity_temperature_st *)arg;
if (copy_to_user(&(tmp->tmperature), &tmper, sizeof(int))) {
PDEBUG("copy_to_user error, %s:%d\n", __FUNCTION__, __LINE__);
return -EFAULT;
}
if (copy_to_user(&(tmp->humidity), &humi, sizeof(int))) {
PDEBUG("copy_to_user error, %s:%d\n", __FUNCTION__, __LINE__);
return -EFAULT;
}
break;
default:
return -EFAULT;
}
return 0;
}
static struct file_operations SHT3x_DIS_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = SHT3x_DIS_ioctl,
};
static struct miscdevice SHT3x_DIS_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = DEVICE_NAME,
.fops = &SHT3x_DIS_fops,
};
static int humidity_temperature_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
char buf_write[3];
int ret ;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
{
dev_err(&client->dev, "Must have I2C_FUNC_I2C.\n");
printk("humidity_temperature_probe failed, Must Sourport I2C_FUNC_I2C\n");
return -ENODEV;
}
if (misc_register(&SHT3x_DIS_dev) != 0) {
printk(KERN_INFO "Could not register misc. dev for SHT3x_DIS\n");
return -ENODEV;
}
buf_write[0]=(HEX_CODE_PERIODIC_DATA_ACQUISITION_MODE_MEDIUM_1MPS>>8)&0XFF;
buf_write[1]=HEX_CODE_PERIODIC_DATA_ACQUISITION_MODE_MEDIUM_1MPS&0XFF;
ret = i2c_master_send(client, buf_write, 2);
if (ret<0 ) {
printk("humidity temperature sensor SHT3x-DIS probe failed\n");
return -ENODEV;
}
printk("humidity_temperature_probe success\n");
gclient=client;
return 0;
}
static int humidity_temperature_remove(struct i2c_client *client)
{
return 0;
}
static const struct i2c_device_id humidity_temperature_SHT3x_DIS_id[] = {
{ DEVICE_NAME, 0 },
{ }
};
static struct i2c_driver humidity_temperature_SHT3x_DIS = {
.probe = humidity_temperature_probe,
.remove = humidity_temperature_remove,
.id_table = humidity_temperature_SHT3x_DIS_id,
.driver = {
.name = DEVICE_NAME,
.owner = THIS_MODULE,
},
};
static int __devinit SHT3x_DIS_init(void)
{
printk("register i2c dev for SHT3x_DIS\n");
i2c_add_driver(&humidity_temperature_SHT3x_DIS);
return 0;
}
static void __exit SHT3x_DIS_exit(void)
{
i2c_del_driver(&humidity_temperature_SHT3x_DIS);
printk("unregister i2c dev for SHT3x_DIS\n");
}
module_init(SHT3x_DIS_init);
module_exit(SHT3x_DIS_exit);
/* Module information */
MODULE_AUTHOR("xiecf");
MODULE_DESCRIPTION("SHT3x_DIS driver");
MODULE_LICENSE("GPL");
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