标签:c-3 linux raspberry-pi
我目前在Raspberry Pi计算机上运行一段C代码.它是一个随机数发生器,从连接到GPIO数字输入18的Geiger计数器读取.它生成随机位(请参见代码),并以8为一组的方式打印这些位.此外,每隔30秒,它会打印观察到的辐射的当前水平. .该代码似乎工作正常,除非带走了辐射源.随机数生成的速度较慢,但似乎也会减慢其余任务的速度.在程序开始时打印的消息不会出现,直到生成一个随机数.发生这种情况时,不会显示任何数字,但是会添加一个没有数字的换行符.即使程序正在运行,辐射水平似乎也会每30秒打印一次,但也会在下一个随机数上显示.为什么C以错误的顺序执行代码?
#include <wiringPi.h>//library for I/O
#include <stdlib.h>
int main(int argc, char *argv[])
{
int lastRead;//if this is first time observing current pulse
int pulseCount = 0;//number of total pulses from Geiger counter
long timing[4] = {0,0,0,0};//values to compare to produce one bit
int bits[8] = {0,0,0,0,0,0,0,0};//the newest number
int bitCount = 0;//counts how many random bits have been made
int i = 0;
float startTime = 0;//start of the clock
float currentSec = 0;
float currentMin = 0;
float cpm = 0;
long elapsedTime = 0;
wiringPiSetupGpio();//establish physical connection
pinMode(18, INPUT);//set pin 18 to be input
printf("random\tradiation");
while(1)
{
if( millis()-startTime >= 30000)//30 sec passed?
{
startTime = millis();
currentSec = startTime/1000;
currentMin = currentSec/60;
cpm = pulseCount/currentMin;//calculate counts/min in several steps
printf("\t%f", cpm);//output counts/min
}
if( digitalRead(18) == HIGH )//pin is reading high
{
if(lastRead==0)//is not reading the same pulse again
{
lastRead = 1;//pulse has been identified
timing[pulseCount%4] = millis();//save the time
pulseCount++;//pulse detected
if( pulseCount%4 == 0 )//if times have been collected
{
if( timing[1]-timing[0] > timing[3]-timing[2] )//make a random bit
{
bits[bitCount%8] = 0;//nth bit of set of 8 is 0
}
else {
bits[bitCount%8] = 1;//it is one
}
bitCount++;//note that a bit was added
if( bitCount%8 == 0 )//every 8 bits made
{
printf("\n");
for( i = 0; i < 8; i++)//print them on a new line
{
printf("%d", bits[i]);
}//for
}//if(bitCount%8==0)
}//if(pulseCount%4==0)
}//if(lastRead==0)
}//if(digitalRead(18)==TRUE)
else {
lastRead = 0;//ready to read new pulse
}//else
}//while
}//main()
解决方法:
默认情况下,stdout上的输出在写入终端时是行缓冲的.这意味着输出将一直保存在内存中,直到您打印换行符或调用fflush(stdout)(或输出缓冲区已满-通常为4K或8K字符)为止.
因此,将fflush(stdout)放在要显示累积输出的位置.或使用setbuf(stdout,NULL)完全禁用缓冲.
标签:c-3,linux,raspberry-pi 来源: https://codeday.me/bug/20191012/1896849.html
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