SD Card on a Wemos Mega +WiFi R3 Module ATmega2560+ESP8266

Using Arduino Storage
#1

Hi, having got over my inital problems with the Wemos® Mega +WiFi R3 Module ATmega2560+ESP8266 I am now moving onto the next steps which is adding an SD Card to the board.

The SD Card module I got where these from Banggood

From looking at the details it tells me it has a 5v-3.3v regulator built in, so I should not need to level shift (I presume so though I am a noob with memory issues so I could be wrong)

I have added the sd card module and connected the pins to…

  • MISO - 50
  • SCK - 52
  • MOSI - 51
  • CS - 53
  • Vcc to Mega 5v
  • Gnd to Mega Gnd

I then uploaded a simple script to the Mega but I just can not get the SD to initialised. The SD Card I have tried are all Fat32 formatted and in various sizes 2Gb, 4Gb 32Gb

The script I used was

#include <SPI.h>
#include <SD.h>

int CS_PIN = 53;

File file;

void setup()
{

  Serial.begin(57600);

  initializeSD();
  createFile("test.txt");
  writeToFile("This is sample text!");
  closeFile();

  openFile("prefs.txt");
  Serial.println(readLine());
  Serial.println(readLine());
  closeFile();
}

void loop()
{
}

void initializeSD()
{
  Serial.println("Initializing SD card...");
  pinMode(CS_PIN, OUTPUT);

  if (SD.begin())
  {
    Serial.println("SD card is ready to use.");
  } else
  {
    Serial.println("SD card initialization failed");
    return;
  }
}

int createFile(char filename[])
{
  file = SD.open(filename, FILE_WRITE);

  if (file)
  {
    Serial.println("File created successfully.");
    return 1;
  } else
  {
    Serial.println("Error while creating file.");
    return 0;
  }
}

int writeToFile(char text[])
{
  if (file)
  {
    file.println(text);
    Serial.println("Writing to file: ");
    Serial.println(text);
    return 1;
  } else
  {
    Serial.println("Couldn't write to file");
    return 0;
  }
}

void closeFile()
{
  if (file)
  {
    file.close();
    Serial.println("File closed");
  }
}

int openFile(char filename[])
{
  file = SD.open(filename);
  if (file)
  {
    Serial.println("File opened with success!");
    return 1;
  } else
  {
    Serial.println("Error opening file...");
    return 0;
  }
}

String readLine()
{
  String received = "";
  char ch;
  while (file.available())
  {
    ch = file.read();
    if (ch == '\n')
    {
      return String(received);
    }
    else
    {
      received += ch;
    }
  }
  return "";
}

I then tried using the Mega 3.3v instead of the 5v and it still does not initialised.

I tried using a different pin for the CS but still does not get initialised.

The thing that is bugging me is that if I use my Uno (using the pins of the uno 10, 11, 12, 13) then the SD can be initialised and be write/read fine.

I have read many posts and tried various other things but to no avail.

any help or opinion would be most greatfull.

#2

The SD library defaults to using pin 4 for CS. If you're using a pin other than 4, you should specify it as a parameter to SD.begin():
https://www.arduino.cc/en/Reference/SDbegin

#3

Thanks for the reply. I added CS_PIN to the SD call

eg if (SD.begin(CS_PIN)) but still I can not initialise the SD Card. I even tried using pin 4 on the Mega and changing CS_PIN to 4 but still nothing.

Just don't know why yet but any other possible solutions or comments will still be gratefully received.

#4

use 53 if you connected CS to 53. if you use 4, you must set 53 as OUTPUT for SPI in master mode.

try the CardInfo example

#5

Try using 49 pins instead of 53 and check the Vin electricity for sure.

#6

taweetra:
Try using 49 pins instead of 53 and check the Vin electricity for sure.

just so? some arguments? any reason?

#7