飛凌嵌入式ElfBoard ELF 1板卡-使用AHT20進行環(huán)境監(jiān)測之編寫程序

編程步驟

（一）打開設備

fd = open(AHT20_DEV, O_RDWR);

if(fd < 0) {

printf("can't open file %srn", AHT20_DEV);

return -1;

}

設置宏定義AHT20_DEV為設備節(jié)點/dev/aht20，使用open以可讀寫的方式打開，如果打開錯誤返回-1。

（二）讀取數(shù)據(jù)

ret = read(fd, databuf, sizeof(databuf));

read函數(shù)的作用是把從設備中讀取到的數(shù)據(jù)存到databuf數(shù)組中。

（三）數(shù)據(jù)類型轉(zhuǎn)換

c1 = databuf[0]*1000/1024/1024;  //

t1 = databuf[1] *200*10/1024/1024-500;

hum = (float)c1/10.0;

temp = (float)t1/10.0;

因為溫濕度不能用常量表示，所以需要做相應數(shù)學計算轉(zhuǎn)換成浮點量。

（四）關閉設備

close(fd);

詳細代碼

elf1_cmd_aht20.c：

#include "stdio.h"

#include "unistd.h"

#include "sys/types.h"

#include "sys/stat.h"

#include "sys/ioctl.h"

#include "fcntl.h"

#include "stdlib.h"

#include "string.h"

#include <poll.h>

#include <sys/select.h>

#include <sys/time.h>

#include <signal.h>

#include <fcntl.h>




#define AHT20_DEV "/dev/aht20"




int main(int argc, char *argv[])

{

int fd;

unsigned int databuf[2];

int c1,t1;

float hum,temp;

int ret = 0;




fd = open(AHT20_DEV, O_RDWR);

if(fd < 0) {

printf("can't open file %srn", AHT20_DEV);

return -1;

}




while (1) {

ret = read(fd, databuf, sizeof(databuf));

if(ret == 0) { /* ?????? */




 c1 = databuf[0]*1000/1024/1024;  //

 t1 = databuf[1] *200*10/1024/1024-500;

 hum = (float)c1/10.0;

 temp = (float)t1/10.0;




printf("hum = %0.2f temp = %0.2f rn",hum,temp);

usleep(500000);

}

}

close(fd);

return 0;

}