Question

我正在构建一个程序，它在pin0上对模拟电压进行10次测量并将其打印到日志文件中。当我尝试确保文件为空时，我遇到的问题就出现了。我正在使用SD.remove()来删除以前的日志文件。当我这样做时，新的日志文件永远不会被写入。当我删除对SD.remove()的调用时，程序正常工作。这是SD库中的一些已知错误，还是有一些偷偷摸摸的方法呢？

代码如下。

#include <SD.h>
#define OUTPUT_PIN 9 //Using SparkFun MP3 shield
#define DEFAULT_OUTPUT 10
#define VOLTAGE_REF (5)

//Reads a voltage on pin0. by default, the reference voltage is set to 5 V, but
//it can be changed by changing VOLTAGE_REF.

void setup() {
    Serial.begin(9600);
    Serial.println("Program Initialized");

    pinMode(DEFAULT_OUTPUT ,OUTPUT); //Needs to be on to use the library
    pinMode(0, INPUT);

    if (!SD.begin(OUTPUT_PIN)) {
        //init error
        Serial.println("Error initializing SD card. Reset the Arduino and try again");
        return;
    }

    Serial.println("Card sucessfully initialized");

    if (SD.exists("LOGFILE.LOG") {
        SD.remove("LOGFILE.LOG"); //We don't want to use the same file <<THIS IS THE BUG?
    }

    delay(10); //Make sure changes are applied

    File logFile = SD.open("ANALOG.LOG", FILE_WRITE); //Create a new one every time
    if (!SD.exists("LOGFILE.LOG")) {
        Serial.println("There was some error making a new instance of the logfile?");
        delay(1000);
        SD.open("ANALOG.LOG", FILE_WRITE);
    }
    int i;

    if (logFile) {
        for(i=0;i<10;i++) {
            int j = 0;
            char str[64];

            Serial.print("Reading analog sensor value");
            for(j=0;j<=i;j++) {
                Serial.print(".");
            }
            Serial.println();

            logFile.print("Read #");
            logFile.print(i+1);
            logFile.print(" : ");
            logFile.print(doVoltageRead(0));
             unsigned char l = logFile.println(" V");
             if (!l)
                 Serial.println("No data written");
             delay(500);
        }
        Serial.println("Done.");
        logFile.close(); //Close the logfile
        Serial.println("Data sucessfully written");
    }
    else {
        //Couldn't create file
        Serial.println("There was an error creating the logfile");
    }
}

void loop() {
    //We don't really need to do anything here
}

float doVoltageRead(int pin) {
    int voltageRead = analogRead(pin);
    double divisor = (voltageRead * 0.00097752);
    float finalVoltage =(VOLTAGE_REF * divisor);
    Serial.println(finalVoltage);
    return finalVoltage;
}

Answer 1

所以..首先你看看LOGFILE.LOG是否存在，如果你删除了ANALOG.LOG。然后你创建ANALOG.LOG。之后，检查LOGFILE.LOG是否存在。如果没有，则打印错误并打开ANALOG.LOG。

LOGFILE.LOG的目的究竟是什么？你不应该只将LOGFILE改为ANALOG吗？

Answer 2

我找到了错误的来源。在打开新日志文件后调用if(SD.exists())时，库不喜欢这样。我假设SD.exists()只是检查open返回的地址或对象是否为NULL。但是，在文件已经打开时调用它会导致一些奇怪的行为。在打开内部删除该调用后，一切都很顺利。感谢所有的建议！

在Arduino中使用SD.remove（）和SD库

2 个答案: