从串口读取

Question

这是http://www.gravitech.us/7segmentshield.html给出的代码。

void SerialMonitorPrint (byte Temperature_H, int Decimal, bool IsPositive)
{
Serial.print("The temperature is ");
if (!IsPositive)
{
  Serial.print("-");
}
Serial.print(Temperature_H, DEC);
Serial.print(".");
Serial.print(Decimal, DEC);
Serial.print(" degree C");
Serial.print("\n\n");
}

while(1)
{
    char buffer[100];
    int chars_read = read(fd, &buffer, sizeof(buffer));
    buffer[chars_read] = '\0';
    printf("%s", buffer);
}

那么怎样才能逐行阅读呢？

Answer 1

您不能保证对read的一次调用就能得到一行文本。您需要缓冲数据。最简单的方法是一次读取一个字符，并在到达换行符时停止。如果希望每次读取尽可能多的字符，缓冲代码就会变得更加复杂。

尝试这样开始：

char buffer[100] = {0};
int pos = 0;

while( pos < 99 ) {
    read(fd, buffer+pos, 1);           // Note you should be checking the result
    if( buffer[pos] == '\n' ) break;
    pos++;
}

// Normally you would null-terminate string, but noticed I initialised the
// buffer to all zeroes at the beginning.  So this is not strictly necessary.
// However, in this case it will remove the newline character.
buffer[pos] = 0;