感測器(五) 使用Arduino Mega2560作SD卡的資料紀錄(Datalogger)－魚的方舟圖形語言的世界 - LabVIEW & Arduino & Python工作室 - 新網站https://labview-tech.blogspot.com/

與前篇文章一樣，SD卡不是感測器，但因是在同一類主題中討論，故列入。

用Mega2560試了SD Datalogger好幾次，今天終於成功，

網路上的討論很多，我列出我是成功的參數：

首先根據註解：

// On the Ethernet Shield, CS is pin 4. Note that even if it's not
// used as the CS pin, the hardware CS pin (10 on most Arduino boards,
// 53 on the Mega) must be left as an output or the SD library
// functions will not work.

也就是說const int chipSelect = 53; --> For Mega2560

再來根據Sd2PinMap.h中關於Mega2560腳位的定義，

#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
// Mega

// Two Wire (aka I2C) ports
uint8_t const SDA_PIN = 20;
uint8_t const SCL_PIN = 21;

// SPI port
uint8_t const SS_PIN = 53;
uint8_t const MOSI_PIN = 51;
uint8_t const MISO_PIN = 50;
uint8_t const SCK_PIN = 52;

所以基本上依據上述的條件做調整，SD card可以成功的寫入，

不過很奇怪的是，我用Mega2560比UNO在寫入時lost的比較少。

Code:

/*
SD card datalogger

This example shows how to log data from three analog sensors
to an SD card using the SD library.

The circuit:
* analog sensors on analog ins 0, 1, and 2
* SD card attached to SPI bus as follows:
* For UNO
** MOSI - pin 11
** MISO - pin 12
** CLK - pin 13
** CS - pin 10
*For Mega2560
** MOSI - pin 51
** MISO - pin 50
** CLK - pin 52
** CS - pin 53

created 24 Nov 2010
modified 9 Apr 2012
by Tom Igoe

This example code is in the public domain.

*/

#include <SD.h>

// On the Ethernet Shield, CS is pin 4. Note that even if it's not
// used as the CS pin, the hardware CS pin (10 on most Arduino boards,
// 53 on the Mega) must be left as an output or the SD library
// functions will not work.
const int chipSelect = 53;

void setup()
{
// Open serial communications and wait for port to open:
Serial.begin(9600);
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
}

Serial.print("Initializing SD card...");
// make sure that the default chip select pin is set to
// output, even if you don't use it:
pinMode(53, OUTPUT); //10 for UNO, 53 for Mega2560

// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
    return;
}
Serial.println("card initialized.");

// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
if (SD.exists("datalog.txt")) {
    Serial.println("datalog.txt exists.");
}
else {
    Serial.println("datalog.txt doesn't exist.");
}

// open a new file and immediately close it:
Serial.println("Creating datalog.txt...");

File dataFile = SD.open("datalog.txt", FILE_WRITE);
}

void loop()
{
// make a string for assembling the data to log:
String dataString = "";

// read three sensors and append to the string:
for (int analogPin = 0; analogPin < 3; analogPin++) {
    int sensor = analogRead(analogPin);
    dataString += String(sensor);
    if (analogPin < 2) {
      dataString += ",";
    }
}

File dataFile = SD.open("datalog.txt", FILE_WRITE);
//delay(1000);
// if the file is available, write to it:
if (dataFile) {
    dataFile.println(dataString);
    dataFile.close();
    // print to the serial port too:
    Serial.println(dataString);
    delay(1000);
}
// if the file isn't open, pop up an error:
else {
    Serial.println("error opening datalog.txt");
}
}