用stdio写入文件

我正在使用来自connectionPi库的示例代码，以通过串行从Arduino到Raspberry Pi读取数据，它可以正确显示数据，printf("%c", newChar);但无法将相同数据写入文本文件。

这是整个文件：

 /*
 Pi_Serial_test.cpp - SerialProtocol library - demo
 Copyright (c) 2014 NicoHood.  All right reserved.
 Program to test serial communication

 Compile with:
 sudo gcc -o Pi_Serial_Test.o Pi_Serial_Test.cpp -lwiringPi -DRaspberryPi -pedantic -Wall
 sudo ./Pi_Serial_Test.o
 */

// just that the Arduino IDE doesnt compile these files.
#ifdef RaspberryPi

//include system librarys
#include <stdio.h> //for printf
#include <stdint.h> //uint8_t definitions
#include <stdlib.h> //for exit(int);
#include <string.h> //for errno
#include <errno.h> //error output

//wiring Pi
#include <wiringPi.h>
#include <wiringSerial.h>

char device[]= "/dev/ttyAMA0";
// filedescriptor
int fd;
unsigned long baud = 9600;
unsigned long timeTemp=0;
unsigned long timeHum=0;
//unsigned long timeLight=0;
//unsigned long timeMotion=0;


//prototypes
int main(void);
void loop(void);
void setup(void);

void setup(){
  printf("%s \n", "Raspberry Startup!");
  fflush(stdout);

  //get filedescriptor
  if ((fd = serialOpen (device, baud)) < 0){
    fprintf (stderr, "Unable to open serial device: %s\n", strerror (errno)) ;
    exit(1); //error
  }

  //setup GPIO in wiringPi mode
  if (wiringPiSetup () == -1){
    fprintf (stdout, "Unable to start wiringPi: %s\n", strerror (errno)) ;
    exit(1); //error
  }

}

void loop() {
  // Temperature every 3 seconds
  if(millis()-timeTemp>=3000){
    serialPuts (fd, "05\n");
    // you can also write data from 0-255
    // 65 is in ASCII 'A'
    //serialPutchar (fd, 5);
    timeTemp=millis();
  }

  // read signal
  if(serialDataAvail (fd)){
    char newChar = serialGetchar (fd);
    FILE * writeTemp = fopen("temp.txt", "w");
    printf("%c", newChar);
    fputc(newChar, writeTemp);
    fflush(stdout);
    fclose(writeTemp);
    }


// Humidity every 4 seconds
  if(millis()-timeHum>=4000){
    serialPuts (fd, "06\n");
    // you can also write data from 0-255
    // 65 is in ASCII 'A'
    //serialPutchar (fd, 5);
    timeHum=millis();
  }

  // read signal
  if(serialDataAvail (fd)){
    char newChar = serialGetchar (fd);
    //printf("received from ardiono \n");
    printf("%c", newChar);
    fflush(stdout);
    }



  }

// main function for normal c++ programs on Raspberry
int main(){
  setup();
  while(1) loop();
  return 0;
}

#endif //#ifdef RaspberryPi

我尝试了不同的命令，但是由于从const char *到char或FILE的无效转换，我不断遇到错误。

我只需要从printf("%c", newChar);文件中写入数据即可。