ho modificato il programma in modo che il pin cs sia sul piedino n°53.
no, nessuna modifica, i pin corretti sono
pinMode(SS_PIN, OUTPUT);
digitalWrite(SS_PIN, HIGH);
pinMode(10, OUTPUT); // Set the CS pin as an output
digitalWrite(10, 1); // Turn off the W5100 chip! (wait for configuration)
pinMode(4, OUTPUT); // Set the SDcard CS pin as an output
digitalWrite(4, 1); // Turn off the SD card! (wait for configuration)
ciao