SDfat + digitalRead = SD card failure

Hi All,

I’m stumped. I have a program that is supposed to read a configuration file from the SD card and then validate and store the values into EEPROM. It should do this when a mechanical switch is activated at boot time. The problem I have is that if I use a mechanical switch on any pin (I’ve tried A0, A1, 1) then the SD card fails. If I put in a programmatic switch, everything works properly.

Here is the pertinent bits of code…

#define RECONFIG 0  // force a reconfig if '1', '0' for normal run

#include <NewSoftSerial.h>
#include <TinyGPS.h>
#include <PWMServo.h>
#include <EEPROM.h>
#include <EEPROMAnything.h>
#include <LiquidCrystal.h>
#include <SdFat.h>

/* Pin assignments */
static const int SD_ss = 10;  // SD card select
static const int reconfig_pin = 1;                        

/* File name and directory assignments */
static const char* GameConfigName = "Game.cfg";

/* ********************************************************************* 
 * function to parse the configuration file into its component parts of
 * the configuration struct
int readGameSettings(struct config_t *gameSettings) {
  char  *myinput;
  char bigstring[151]="";

  Msg(lcd, "Reading", "Settings", 2000);

  // open the Game.cfg file. 
  SdFile myFile(GameConfigName, O_READ);
  if (!myFile.isOpen()) { // Open failed
    Msg(lcd, "Cfg File", "Failure2", 2000);
  //  return 1;

void setup() {

  // Initialize the SD card
  pinMode(SD_ss, OUTPUT);
  if (!sd.init(SPI_HALF_SPEED, SD_ss)) {
    Msg(lcd, "SD card", "failed!", 2000);
    badSD = 1;

    // Do we need to reconfigure the system
  if ((digitalRead(reconfig_pin) == HIGH) || (RECONFIG == 1)){          // time to reconfigure   --- Config switch set to "Config"
    if (badSD) {  // We need to reconfigure but can't read the SD card
      Msg(lcd, "SD card", "failure", 5000);

    // Read game settings from SD card
    if (readGameSettings(&gameSettings) == 1) {  // failure during setup
      Msg(lcd, "Settings", "incorrect", 2000);

So I obviously cut out most of the program but those are the bits that are failing.

Scenario, if I use the programatic switch and “#define RECONFIG 1” then everything works no matter the state of the physical switch. If I “#define RECONFIG 0” and leave the physical switch “off” then the SD card and other files can be read/written to without problem. But if I turn on the physical switch then the program can no longer access the SD card and I get the error message “Cfg File Failure2”.

For the mechanical switch to be “on” I’ve tried using internal pull-up resister with the switch-pin going to ground; I’ve tried external pull-up resistors (10K and 22K); I’ve tried external pull-down resistors with the switch-pin going to 5v. Same symptoms on every attempt.

Does anyone have any ideas what might be going on? BTW, I’ve tried a different Arduino and I’ve used this SD card and card-reader in other programs and they all work fine.
IDE 0022. Arduino Uno.

Thanks in advance for any help anyone might give!!

Pin D1 is one of the serial port pins. Don't use it for your switch.

Thanks for the reply, John. I've also tried A0 and A1 and they both behaved the same way. But I will move it back to one of them to get it off 1.