飛凌嵌入式ElfBoard ELF 1板卡-使用AHT20進(jìn)行環(huán)境監(jiān)測(cè)之編寫(xiě)程序

編程步驟

（一）打開(kāi)設(shè)備

fd = open(AHT20_DEV, O_RDWR);

if(fd < 0) {

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

return -1;

}

設(shè)置宏定義AHT20_DEV為設(shè)備節(jié)點(diǎn)/dev/aht20，使用open以可讀寫(xiě)的方式打開(kāi)，如果打開(kāi)錯(cuò)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(shè)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?yàn)闇貪穸炔荒苡贸Ａ勘硎荆孕枰鱿鄳?yīng)數(shù)學(xué)計(jì)算轉(zhuǎn)換成浮點(diǎn)量。

（四）關(guān)閉設(shè)備

close(fd);

詳細(xì)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;

}