greets
so I've hooked up the SD card module to the Arduino UNO pins through resistor/zener diode level shifters.
the resistors are 1K and 3.3V zener diodes.
my SD card module, from eBay (China).
I powered it from the 5V pin on the UNO.
I've used the sketch Read/Write but other sketches from the Arduino SD folder also give the same error:
Initializing SD card...initialization failed!
here is the sketch itself [I only added the two 1000ms delays because I wanted to use my scope to see what's happening on the SPU lines]
/*
This example shows how to read and write data to and from an SD card file
The circuit:
* SD card attached to SPI bus as follows:
** MOSI - pin 11
** MISO - pin 12
** CLK - pin 13
** CS - pin 4
*/
#include <SD.h>
File myFile;
void setup()
{
Serial.begin(9600);
delay(1000);
Serial.print("Initializing 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);
if (!SD.begin(4)) {
delay(1000);
Serial.println("initialization failed!");
return;
}
delay(1000);
Serial.println("initialization done.");
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
myFile = SD.open("test.txt", FILE_WRITE);
// if the file opened okay, write to it:
if (myFile) {
Serial.print("Writing to test.txt...");
myFile.println("testing 1, 2, 3.");
// close the file:
myFile.close();
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
// re-open the file for reading:
myFile = SD.open("test.txt");
if (myFile) {
Serial.println("test.txt:");
// read from the file until there's nothing else in it:
while (myFile.available()) {
Serial.write(myFile.read());
}
// close the file:
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
}
void loop()
{
// nothing happens after setup
}
as you can see on the scope screen shots the voltages on the MOSI, MISO and SCK lines are wrong, the CS is ok.
I've tried other diodes and resistors and it's the same thing. Am I overlooking something?
