ファイル記述子を閉じずに、Beaglebone Black または別の組み込み Linux システムの ADC を読み取ることは可能ですか?
前にselectで試してみましたread()。select()1 をread()返しますが、最初の繰り返しの後に 0 を返すため、データを取得できません。何か案は？ファイル記述子を閉じたり開いたりするには、多くの CPU パワーが必要ですか?
私のコード:
#include<iostream>
#include<fstream>
#include<string.h>
#include<sstream>
#include<fcntl.h>
#include<unistd.h>
#include<sys/select.h>
#include <sys/time.h>
using namespace std;
#define LDR_PATH "/sys/bus/iio/devices/iio:device0/in_voltage"
int main(int argc, char* argv[]){
int number = 1;
int AdcConnection = 0;
stringstream AdcPath;
AdcPath << LDR_PATH << number << "_raw";
AdcConnection = open(AdcPath.str().c_str(),O_RDONLY |O_NONBLOCK);
if (AdcConnection <0)
{
perror("UART: Failed to open the file.\n");
close(AdcConnection);
return -1;
}
fd_set fdsAdcRead;
struct timeval timeout = {5, 0};
unsigned char receive[5];
int FlagRead = -1;
int FlagSelect = -1;
while (1)
{
FD_ZERO(&fdsAdcRead); //clear the file descriptor
FD_SET(AdcConnection,&fdsAdcRead); //Set the descriptor
FlagSelect = select(AdcConnection+1,&fdsAdcRead,NULL,NULL,&timeout);//check if data are available
if (FlagSelect <0)
{
perror("Failed to check if data are available.\n");
close(AdcConnection);
return -1;
}
else if (FlagSelect ==0)
{
cout << "There were no Data" << endl;
timeout.tv_sec = 5;
}
else
{
memset(&receive,0,sizeof(receive));
FlagRead = read(AdcConnection, (void*)receive, 5);
cout << receive << endl << FlagRead << FlagSelect << endl;
timeout.tv_sec = 5;
}
usleep(1000000);
}