ATSam3x8e (Due) LED pins as digital I/O

Other Hardware 3rd Party Boards
1

Hi Guys,

I am using the Arduino Due micro controller (ATSam3x8e) as part of a custom PCB (build by a different engineer). I was just wondering if there would be any issues using the the LED pins D13, D72 and D73 as extra I/0. Because the chip isn't on a Due the LED pins are are not wired to anything, hopefully this is not a silly question but I wasn't sure if they might be assigned and used internally by the chip or if it just sees them as more configurable I/O

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All I/O pins can be configured as Input or Output with PIO.

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Thanks for the reply, so am I right in saying that it would be safe to use these 3 pins to fire external relays etc and not have any issues? thanks again

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CyberOddity:
Thanks for the reply, so am I right in saying that it would be safe to use these 3 pins to fire external relays etc and not have any issues? thanks again

Nope.

  1. You would need to recompile a unique Arduino core to remove the references to all three of those pins. It would be painful and break future compatibility, not worth the hassle IMO.

  2. You need to be careful with your I/O pin selection on the sam3x8. This is not a typical AVR device that can sink/source 20+ ma out of any pin, you’ve got both high and low current pins where high is source 15ma (Max), sink 9 and low current pins that can only source 3 and sink 6. That is detailed on the pinout diagram in your other post.

  3. All three pins you reference are low current pins and D72/D73 have led’s hanging on the pins and are not broken out to headers. You’d have solder wires to led pads for access to those pins.

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WattsThat:
Nope.

  1. You would need to recompile a unique Arduino core to remove the references to all three of those pins. It would be painful and break future compatibility, not worth the hassle IMO.

  2. You need to be careful with your I/O pin selection on the sam3x8. This is not a typical AVR device that can sink/source 20+ ma out of any pin, you’ve got both high and low current pins where high is source 15ma (Max), sink 9 and low current pins that can only source 3 and sink 6. That is detailed on the pinout diagram in your other post.

  3. All three pins you reference are low current pins and D72/D73 have led’s hanging on the pins and are not broken out to headers. You’d have solder wires to led pads for access to those pins.

Hey WattsThat, thanks for the replies, they really help a lot. That's too bad about the LED's being tied to the MCU, I was hoping because I'm using it on a custom board I might get away with stealing them for a few extra I/O. I have some spare I/O already so I will leave the LED's as they are. Also thanks for the advise on pin selection, I did notice that, the previous engineer that designed the board did actually use some low current pins to fire relays (which I won't need to do again) and had no issues so hopefully that wont impact me.