一.SD5075芯片简介

SD5075 是一款高准确度温度传感器芯片内含高精度测温 ADC，在-40C ~+100°C 范围内典型误差小于+0.5°C，在-55C~+125°C 范围内典型误差小于士1.0°C。通过两线 IC/SMBus接口可以很方便与其他设备建立通信。设置 A2~A0 的地址线，可支持8 片芯片并联总线连接
本芯片可选 3 种工作模式: 连续测温模式单次测温模式，关断模式。可根据速度或功耗的需求灵活选择和配置。

管脚描述：

                                 

二.SD5075温度检测原理

原理：

SD5075芯片经过ALARM引脚检测温度的变化，经过模数转换器的转换，把温度值写入寄存器中，SOC再通过IIC读取寄存器的值，从而拿到温度值。

寄存器列表：

通过配置0x01寄存器为0x00，通过寄存器0x00读取到温度结果。

三.代码实现

#include <linux/miscdevice.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include <linux/printk.h>
#include <linux/kobject.h>
#include <linux/version.h>#define DRIVER_VERSION KERNEL_VERSION(0, 0x01, 0x00)
#define DRIVER_NAME "IST_TEMP"/*define logging*/
#define IST_TEMP_DEBUG	0
#if IST_TEMP_DEBUG
#define DBG(format, args...)					\printk(KERN_DEBUG "%s: " format, DRIVER_NAME, ##args)
#define ERR(format, args...)					\printk(KERN_ERR "%s: " format, DRIVER_NAME, ##args)
#define WARNING(format, args...)				\printk(KERN_WARN "%s: " format, DRIVER_NAME, ##args)
#define INFO(format, args...)					\printk(KERN_INFO "%s: " format, DRIVER_NAME, ##args)
#else
#define DBG(format, args...)
#define ERR(format, args...)
#define WARNING(format, args...)
#define INFO(format, args...)
#endifstruct temp_dev {struct device *dev;struct miscdevice miscdev;struct i2c_client *client;u32 value;
};struct temp_dev *g_temp;
struct temp_dev *temp;
static int last_value = 0;//charstatic void i2c_wr(struct temp_dev *temp, u16 reg, u8 *val, u32 n)
{struct i2c_msg msg;struct i2c_client *client = temp->client;int err;u8 data[128];data[0] = reg;memcpy(&data[1], val, n);msg.addr = client->addr;msg.flags = 0;msg.buf = data;msg.len = n + 1;err = i2c_transfer(client->adapter, &msg, 1);if (err != 1) {ERR("%s: writing register 0x%x from 0x%x failed\n", __func__,reg, client->addr);} else {switch (n) {case 1:INFO("I2C write 0x%02x = 0x%02x\n", reg, data[1]);break;case 2:INFO("I2C write 0x%02x = 0x%02x%02x\n", reg, data[2],data[1]);break;case 4:INFO("I2C write 0x%02x = 0x%02x%02x%02x%02x\n", reg,data[4], data[3], data[2], data[1]);break;default:INFO("I2C write %d bytes from address 0x%02x\n", n,reg);}}
}static void i2c_rd(struct temp_dev *temp, u16 reg, u8 *val, u32 n)
{struct i2c_msg msg[2];struct i2c_client *client = temp->client;int err;u8 buf[1] = { reg };/*msg[0] addr to read*/msg[0].addr = client->addr;msg[0].flags = 0;msg[0].buf = buf;msg[0].len = 1;/*msg[1] read data*/msg[1].addr = client->addr;msg[1].flags = I2C_M_RD;msg[1].buf = val;msg[1].len = n;err = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));if (err != ARRAY_SIZE(msg)) {ERR("%s: reading register 0x%x from 0x%x failed\n", __func__,reg, client->addr);}
}static void i2c_rd8(struct temp_dev *temp, u16 reg, u8 *val)
{i2c_rd(temp, reg, val, 1);
}static void i2c_wr8(struct temp_dev *temp, u16 reg, u8 buf)
{i2c_wr(temp, reg, &buf, 1);
}static void i2c_wr_word(struct temp_dev *temp, u16 reg, u16 val)
{unsigned char data[2] = {0};data[0] = (unsigned char)(val & 0xFF);data[1] = (unsigned char)((val & 0xFF00) >> 8);i2c_wr(temp, reg, data, 2);
}static void i2c_rd_word(struct temp_dev *temp, u16 reg, u8 *val)
{i2c_rd(temp, reg, val, 2);
}static long temperature_ioctl(struct file *file, uint32_t cmd, unsigned long arg)
{return 0;
}static ssize_t temperature_write(struct file *file, const char __user *buf,size_t size, loff_t *ppos)
{return 1;
}static ssize_t temperature_read(struct file *file, char __user *buf, size_t size,loff_t *ppos)
{return 1;
}static ssize_t temperature_value_read(struct device *dev,struct device_attribute *attr, char *buf)
{struct temp_dev *temp = g_temp;int result = -1;unsigned char reg;unsigned char reg_value;unsigned short value = 0;unsigned char value1[2] = {0};reg = 0x01;reg_value = 0x00;i2c_wr8(temp, reg, reg_value);reg = 0x00;i2c_rd_word(temp, reg, value1);value = (value1[0]<<8|value1[1])>>4;if(value >= 0x800){printk(" temperature_value_read !!!");value = (value - 2048)>>4;result = value - 128;}else{result = value>>4;printk(" temperature_value_read !!!");}if(result == -1){result -= last_value;printk(" temperature_value_read !!!");if((result > 8) || (result < (-8))){result = last_value;}else{result = -1;}}temp->value = result;return sprintf(buf, "%d\n", temp->value);
}static ssize_t temperature_value_write(struct device *dev,struct device_attribute *attr,const char *buf, size_t count)
{return count;
}static DEVICE_ATTR(value, 0644,temperature_value_read, temperature_value_write);static void temp_init(struct temp_dev *temp)
{}static const struct file_operations temp_fops = {.owner = THIS_MODULE,.read = temperature_read,.write = temperature_write,.unlocked_ioctl = temperature_ioctl,
};struct miscdevice temp_miscdev = {.minor = MISC_DYNAMIC_MINOR,.name = "temp_dev",.fops = &temp_fops,
};static int temp_probe(struct i2c_client *client,const struct i2c_device_id *id)
{struct temp_dev *temp;struct device *dev = &client->dev;int ret;dev_info(dev, " driver version: %02x.%02x.%02x",DRIVER_VERSION >> 16,(DRIVER_VERSION & 0xff00) >> 8,DRIVER_VERSION & 0x00ff);if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))return -EIO;DBG("chip found @ 0x%x (%s)\n", client->addr << 1,client->adapter->name);temp = devm_kzalloc(dev, sizeof(struct temp_dev), GFP_KERNEL);if (!temp)return -ENOMEM;temp->client = client;client->flags |= I2C_CLIENT_SCCB;ret = misc_register(&temp_miscdev);if (ret) {ERR(" temp ERROR: could not register ist_temp device\n");return ret;}ret = device_create_file(temp_miscdev.this_device,&dev_attr_value);if (ret) {dev_err(temp->dev, " failed to create attr hdmirxsel!\n");return ret;}temp_init(temp);g_temp = temp;INFO("%s  found @ 0x%x (%s)\n", client->name, client->addr << 1,client->adapter->name);return 0;
}static int temp_remove(struct i2c_client *client)
{misc_deregister(&temp_miscdev);kfree(temp);return 0;
}static const struct of_device_id temp_of_match[] = {{ .compatible = "temperature" },{}
};
MODULE_DEVICE_TABLE(of, temp_of_match);static struct i2c_driver temp_driver = {.probe = temp_probe,.remove = temp_remove,.driver = {.owner = THIS_MODULE,.name = DRIVER_NAME,.of_match_table = of_match_ptr(temp_of_match),},
};static int __init temp_driver_init(void)
{return i2c_add_driver(&temp_driver);
}static void __exit temp_driver_exit(void)
{i2c_del_driver(&ist_temp_driver);
}device_initcall_sync(temp_driver_init);
module_exit(temp_driver_exit);MODULE_DESCRIPTION("temperature sensor");
MODULE_AUTHOR("");
MODULE_LICENSE("GPL v2");