1.在上报经纬度时由于数据协议限制需要将double型数据存储到无符号数组中，下边是写了一个简单C程序进行验证；

2.代码示例如下

#include <stdio.h>
typedef union
{
	float data;
	unsigned char arr[4];
} my_data;

int main()
{
	my_data test_data = {0};
	
	double jingdu = 121.4736522;
	double weidu = 31.2425864;
	
	test_data.data = jingdu;
	//注意大小端问题
	for(int i = 3; i >= 0; i--)
	{
		printf("1.test_data[%d] = %02X\n",i,test_data.arr[i]);
	}
	printf("\r\n");
	
	test_data.data = weidu;
	//注意大小端问题
	for(int i = 3; i >= 0; i--)
	{
		printf("2.test_data[%d] = %02X\n",i,test_data.arr[i]);
	}
	printf("\r\n");
   /*  Write C code in this online editor and run it. */
   printf("Hello, World! \n");
   
   return 0;
}

3.运行结果

4.下边再提供一种参考别人的写法

gps_position_info.e = 121.4736522;
uint8_t buffer[128];

dDwordToBuf(gps_position_info.e,&buffer[i]);
//将一个DWORD的值写入四个连续内存BYTE中
void dDwordToBuf(float inDword, rt_uint8_t * _pBuf)
{
    *_pBuf++ = *((rt_uint8_t *)(&inDword) +3);
    *_pBuf++ = *((rt_uint8_t *)(&inDword) +2);
    *_pBuf++ = *((rt_uint8_t *)(&inDword) +1);
    *_pBuf   = *((rt_uint8_t *)(&inDword));    
}