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Author Topic: Latest Ethernet shield - used pins, how to bypass restrictions  (Read 1304 times)
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Hi, I'm new in this and I do not understand of pins occupation. I looked at the Eagle PCB file I saw used these pins:

PD2 (digital 2)
PD4 (digital 4)
PB2 (digital 10)
PB3 (ICSP header)
PB4 (ICSP header)
PB5 (ICSP header)
PC6 (ICSP header)

I looked at schematics too and I saw used these pins:
JHIGH
hole number 3 - SS (PB2 - digital 10)
hole number 7 - GND (GND)
hole number 8 - AHREF (AHREF)

JLOW
hole number 1 - PD0 (digital 0) - but not connected
hole number 2 - PD1 (digital 1) - but not connected
hole number 3 - PD2 (digital 2) - but not connected
hole number 4 - PD3 (digital 3) - but not connected
hole number 5 - SD_CS (digital 4)

Official page says:
The onboard microSD card reader is accessible through the SD Library. When working with this library, SS is on Pin 4.
I understand. This means, that digital pin 4 is not available if SD card reader is used present. Someone says: To disable the SD card by switching pin 4 high
  pinMode(4, OUTPUT);
  digitalWrite(4, HIGH);
OK. And continue in reading:  Arduino communicates with both the W5100 and SD card using the SPI bus (through the ICSP header). This is on digital pins 11, 12, and 13 on the Duemilanove and pins 50, 51, and 52 on the Mega. On both boards, pin 10 is used to select the W5100 and pin 4 for the SD card. These pins cannot be used for general i/o.
And now, I'm confused. Which pins are definitively occupied and cannot be used as input or output? Only 4, 10, 11, 12 and 13?

« Last Edit: July 21, 2013, 02:05:37 pm by K5CZ » Logged

Arduino Uno R3, Arduino Mega 2560 R3, Ethermega (R3), and some Ethernet Shields (R3), Chronodots, TMP36 sensors, DS18B20 sensors, LCDs/TFTs, RS232C to learn and play...

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The W5100 "*INT" pin (number 56) goes through a solder jumper to "PD2" (Arduino Pin 2).  If you add that jumper you have to use Pin 2 for the interrupt signal.
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And now, I'm confused. Which pins are definitively occupied and cannot be used as input or output?
On which Arduino?

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Only 4, 10, 11, 12 and 13?
On a 328-based Arduino, yes.
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http://shieldlist.org/arduino/ethernet-v5

Just by chance I found the information that A0 and A1 are used too. I see that those shields is full of surprises...  smiley-eek
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Arduino Uno R3, Arduino Mega 2560 R3, Ethermega (R3), and some Ethernet Shields (R3), Chronodots, TMP36 sensors, DS18B20 sensors, LCDs/TFTs, RS232C to learn and play...

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