Arduino Ethernet shield and SD card

Using Arduino Storage
1

Hi there!
I'm using Arduino Mega R2 with Ethernet shield R2 for some time now, it works flawlessly.
Now I received new Arduino Mega R3 and Ethernet shield R3 and I started having some issues: the same program that works well with Mega R2 + Ether R2, would start up with error reading SD card. I checked the formatting of the (new) card (using SD Formatter, as adviced in other post), tried to use the old card and still the problem would be there. Then I tested some different setups:
(Mega + Shield)
R2 + R2
R2 + R3
R3 + R3

  • I found out that the problem occurs when running with the R3 shield: I will have problem with the SD card not found only if I have no external power supply.
  • If I start with USB power, there will be the SD not found error, if I plug the external power and reset the Mega, still the error will come up; If then I take the SD out and put it back again in and reset the Mega, then it will work.
  • With R2 + R2 I still get a good result
    Does this makes any sense to anyone?
    Of course I can run the setup with external power supply, but It would be great to know what might be the issue.
    Any ideas?
    Thanks you guys!
2

Can you post the setup() function from your sketch? Sometimes it is the way the two devices are initialized.

3

Hi there!
here goes:

void setup()
{
Serial.begin(9600);
pinMode(10, OUTPUT);
digitalWrite(10, HIGH); //so that SPI will work
pinMode(53, OUTPUT); //so that SPI will work
pinMode(4, OUTPUT);
delay(100); //some time to stabilize outputs

if (!SD.begin(4))
{
Serial.println("SD card failed or not present");.
return;
}
...
}

Thanks!

4

That part looks good. ??

5

Yes, and it works perfectly with Mega R2.
Only with the other combinations I need the external power supply to make it work... hmmm :~