• iCore4T ARM+FPGA双核心板I2C总线挂有三个设备，分别为AXP152电源管理芯片，LM75A温度传感器，EEPROM存储器，在上一个例程中给大家分享了I2C总线驱动的添加过程，今天直接给大家分享LM75A的挂载过程。
• LM75A 是一个使用了内置带隙温度传感器和Σ-△模数转换技术的温度-数字转换器，可用于iCore4T核心板温度监控，如果温度过高可以输出报警信息。

/*
 * Copyright (c) 2006-2018, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2020-02-17     zh.          first version
 */
 
#include <board.h>
#include <drv_qspi.h>
#include <rtdevice.h>
#include <rthw.h>
#include <finsh.h>
 
#ifdef BSP_USING_I2C_LM75A
 
#define LM75A_ADDR						    	(0x90 >> 1)
 
/* For lm75a i2c bus*/
#define LM75A_I2CBUS_NAME     "i2c1"
 
static struct rt_i2c_bus_device *lm75a_i2c_bus = RT_NULL;
 
static rt_err_t i2c_read_nbyte(rt_uint8_t slave_addr, rt_uint8_t cmd, rt_uint8_t *buf, rt_uint32_t len)
{
    rt_i2c_master_send(lm75a_i2c_bus, slave_addr, RT_I2C_WR, &cmd, 1);
 
    rt_i2c_master_recv(lm75a_i2c_bus, slave_addr, RT_I2C_RD, buf, len);
 
    return RT_EOK;
}
 
float lm75a_read(void)
{
	union
	{
		unsigned char buf[2];
		short int value;
	}temp;
	float f;
	unsigned char c;
 
    lm75a_i2c_bus = rt_i2c_bus_device_find(LM75A_I2CBUS_NAME);
 
    if(lm75a_i2c_bus == RT_NULL)
    {
        rt_kprintf("i2c_bus %s for lm75a not found!\n", lm75a_i2c_bus);
        return -RT_ERROR;			
    }
 
	i2c_read_nbyte(LM75A_ADDR,0,temp.buf,2);
 
	c = temp.buf[0];
	temp.buf[0] = temp.buf[1];
	temp.buf[1] = c;
 
	f = temp.value;
	f /= (float)32.0;
	f *= (float)0.125;
 
	return f;
}
static int lm75a(int argc, char **argv)
{
	float tempture;
	int temp;
 
	tempture = lm75a_read();
 
	temp = tempture * 100;
	rt_kprintf("The current temperature is: %d.%02d°\n",temp/100,temp%100);
 
    return RT_EOK;
}
MSH_CMD_EXPORT(lm75a, show current temperature);
#endif /* BSP_USING_I2C_LM75A */

至此，我们成功的挂载了LM75A设备。      

源代码可以移步这里下载：

链接：https://pan.baidu.com/s/1fcLU4WaRDlgr0mNYwZj1Yg 提取码：zstq