My problem is simple yet extremely problematic. For some reason, I cannot interact with an SD card and a LED strip at the same time with my arduino. After hours of testing multiple scripts, I am 99.99% that the issue is due to the SPI.h library. I have tried the simplest LED strip code, such as turning on led number 5. If I include SPI.h, the code does not work, the data LED of the arduino doesn't even light up, the arduino doesn't send anything to the strip data line. If I remove include SPI.h, the code works. This is really odd, I have read about the SPI.h messing with the pins, so now I'm looking for a solution, to use the SD card module without the SPI library if it is possible. Here is an example of a code that does not work due to the use of the SPI.h library.

Any help is greatly appreciated, this is extremely odd and problematic.

#include <Time.h>
#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
#include <avr/power.h>
#include <SPI.h>
#include <SD.h>

Sd2Card card;
SdVolume volume;
SdFile root;

const int chipSelect = 4;

#define PIN            6
#define NUMPIXELS      400

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB +   NEO_KHZ800);

boolean stringComplete = false;  // whether the string is complete
boolean readarray=false;
String inString = "";
int c=0;
int cc=0;
int led=0;
int i=0;
int j=0;
int pixel_n=0;
unsigned long start;
unsigned long endd;

//char* ledd[]={"", "", ""};
int ledd[3]={0,0,0};

File myFile;

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

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

// 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);

Serial.println("Ok we're done");

pixels.setPixelColor(5, (200,200,200)); // THIS DOES NOT WORK
pixels.show(); // THIS EITHER


void loop(void) {


1 Answer 1


I had the same problem with using the SD reader with a SPI SRAM. It turns out that the very cheap SD reader cards do not like multiple SPI components on the same port. Since the Arduino has only one SPI, the only thing that worked was to use a SD data logger card.

To add a tristate solution by using two resistors on the MISO line also did not work in my case.

See my post for the post I created regarding this probably similar problem.

  • thanks a lot for your help. So the only solution is to use a SD logger card as you say. What difference is this going to make? I looked it up and it seems like it does require the SPI.h library as well. Apr 28, 2017 at 7:25
  • 1
    Please add this as a comment to my answer (and upvote if it helps). I know it uses also the SPI library. However, it contains some hardware/circuit that makes it possible to have a second (and possibly more) SPI device on the SPI bus simultaneously. If you know what to 'add' to the non working SD part, please let me know. Apr 28, 2017 at 9:33
  • Hi sorry, I wanted to do add this as an answer, but I didn't have enough reputation. Does it require a lot of tweaking to create another bus on the SD shield or does it automatically allocate it? Apr 28, 2017 at 10:58
  • I don't think you can add another SPI bus. The Arduino (at least the most) only have one (hardware) SPI bus. The SD data logger can be used together with other SPI components, but the cheap SD readers cannot. Apr 28, 2017 at 11:15

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