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Topic: SD library ignoring Chipselect pin (Read 3087 times) previous topic - next topic


I have been trying to diagnose a problem with a breadboard SD connector and noticed the following peculiar behavior when I use a 4gb microSD card in a Sparkfun microSD shield connected to a UNO.  Notice that I have purposely set the ChipSelect pin to pin 1, even though the Sparkfun needs it to be pin 8...  In fact I have changed the Chip Select to every pin between 1,3-10 and all seem to work.  When I run this sketch I get a summary of the card, followed by a list (correct list) of files on the card...

What is going on?

Code: [Select]

  SD card test
This example shows how use the utility libraries on which the'
SD library is based in order to get info about your SD card.
Very useful for testing a card when you're not sure whether its working or not.

The circuit:
  * SD card attached to SPI bus as follows:
** MOSI - pin 11 on Arduino Uno/Duemilanove/Diecimila
** MISO - pin 12 on Arduino Uno/Duemilanove/Diecimila
** CLK - pin 13 on Arduino Uno/Duemilanove/Diecimila
** CS - depends on your SD card shield or module.
Pin 4 used here for consistency with other Arduino examples

created  28 Mar 2011
by Limor Fried
modified 9 Apr 2012
by Tom Igoe
// include the SD library:
#include <SD.h>

// set up variables using the SD utility library functions:
Sd2Card card;
SdVolume volume;
SdFile root;

// change this to match your SD shield or module;
// Arduino Ethernet shield: pin 4
// Adafruit SD shields and modules: pin 10
// Sparkfun SD shield: pin 8
const int chipSelect = 1;   

void setup()
// Open serial communications and wait for port to open:

  Serial.print("\nInitializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output
  // or the SD library functions will not work.
  pinMode(10, OUTPUT);     // change this to 53 on a mega
  pinMode(chipSelect, OUTPUT);

  // we'll use the initialization code from the utility libraries
  // since we're just testing if the card is working!
  if (!card.init(SPI_HALF_SPEED, chipSelect)) {
    Serial.println("initialization failed. Things to check:");
    Serial.println("* is a card is inserted?");
    Serial.println("* Is your wiring correct?");
    Serial.println("* did you change the chipSelect pin to match your shield or module?");
  } else {
   Serial.println("Wiring is correct and a card is present.");

  // print the type of card
  Serial.print("\nCard type: ");
  switch(card.type()) {
    case SD_CARD_TYPE_SD1:
    case SD_CARD_TYPE_SD2:

  // Now we will try to open the 'volume'/'partition' - it should be FAT16 or FAT32
  if (!volume.init(card)) {
    Serial.println("Could not find FAT16/FAT32 partition.\nMake sure you've formatted the card");

  // print the type and size of the first FAT-type volume
  uint32_t volumesize;
  Serial.print("\nVolume type is FAT");
  Serial.println(volume.fatType(), DEC);
  volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
  volumesize *= volume.clusterCount();       // we'll have a lot of clusters
  volumesize *= 512;                            // SD card blocks are always 512 bytes
  Serial.print("Volume size (bytes): ");
  Serial.print("Volume size (Kbytes): ");
  volumesize /= 1024;
  Serial.print("Volume size (Mbytes): ");
  volumesize /= 1024;

  Serial.println("\nFiles found on the card (name, date and size in bytes): ");
  // list all files in the card with date and size
  root.ls(LS_R | LS_DATE | LS_SIZE);

void loop(void) {


Jun 28, 2012, 09:12 pm Last Edit: Jun 28, 2012, 09:22 pm by SurferTim Reason: 1
What makes you think it is ignoring it? Modify the setup routine with this:
Code: [Select]
void setup()

 Serial.print("\nInitializing SD card...");

 // disable SD SPI

 pinMode(10, OUTPUT);
 pinMode(chipSelect, OUTPUT);

 // rest of your setup stuff

Does the SD still respond?

edit: corrected missing comment slash in code.


Pin 1 is one of the serial pins. You are using Serial.print as well, so things will get somewhat confused.

Don't send me technical questions via Private Message.


The Sparkfun card has a hex buffer as a 5V to 3.3V level converter.  If the buffer input pin, pin 8, is not initialized this buffer often pulls CS on the SD card low.  The SD will appear to ignore CS but will likely be flaky since noise may cause pin 8 to go high and disable the SD.

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