Arduino Leonardo + 2 Shields. Pins compatibility?

Projects General Guidance
1

Hi guys, I have an arduino leonardo board and wish to add 2 shields on it.

Following the specs, pins 10,11 and 12 are conflicting, can someone confirm?
I'm kinda new to arduino, but I assume the used pins are defined in the associated libraries?

I tried to take a look at the ethernet shield library (github/arduino-libraries/Ethernet) and could find the pin 10 used for initialization. (Ethernet.init(sspin = 10) so I assume I can easily change it with a free pin like the pin 2?
What about others, can I easily remap them to other pins or is it hardcoded in the hardware?

2

Both boards use the SPI interface which is a bus and you can connect multiple devices (shields in your case) to it. So there is no need to change 11, 12 and 13.

Note that on a Leonardo the SPI interface is not on pins (10),11,12 and 13 but on the 6-pin header.

  1. USB host shield
    I can't find in the schematic (https://www.arduino.cc/en/uploads/Main/USBHostShield-Rev2.pdf) that pins 11, 12 and 13 are used.
  2. Ethernet shield
    The same, schematic https://www.arduino.cc/en/uploads/Main/arduino-Ethernet-Shield2-V2-sch.pdf

It does not look like you can adjust the CS (SS) pin for the host shield library but I might be wrong , you can adjust it in the ethernet library, hack the ethernet shield and route pin 10 to another pin.

4

Hello, thanks for your answer. By hacking what do you mean exactly? Before using it I must init the ethernet shield using Ethernet.init(sspin=10). Can I just change the pin from this parameter?

Also, since you mentionned these 6 headers, I'm wondering if both shields are even connectable without doing some soldering..

IMG_20230322_152946
IMG_20230322_152946676×676 40.1 KB

IMG_20230322_152931
IMG_20230322_152931676×676 44 KB

As you can see both shields don't forward the 6 front pins, so I guess it's a problem?

5

By hacking I mean that you have to cut a trace or pin on the shield that does not allow you to select a CS in software and next solder (or jump) a wire to a different pin.

I will try to look at that tomorrow or the day after as I'm not behind a computer at the moment.

Those shields indeed do not extend the pins so you do have a problem.

7

I think it's too much work for nothing. I mean, you the expert here but I could just use a DUE instead of a LEONARDO what do you think?
DUE natively supports an additionnal USB port for mouse/keyboard support, so it'd just require an ethernet shield over it, am I wrong?
As it's not AVR but SAMD? or yea I mean I figured out it's a different proc, would the ethernet shield used on the picture work on that model as well?

Here the arduino model I mean: Arduino Due — Arduino Official Store

Thanks for your feedbacks

PS: does DUE performances outperforms leonardo?

8

I can't say; the product mage only mentions Uno and Mega.

I'm not familiar with the Due.

It runs on a higher clock; however to execute a certain C++ statement might take more clock cycles. You can easily compile the same sketch for e.g. an Uno and a Due; the Due's reported memory usage (code) is significantly bigger than the Uno's one. E.g. a digitalWrite might result in e.g. 50 machine instructions on an Uno and 200 machine instructions on a Due (numbers are just thumbsuck).

For pure calculations I think it will be a lot faster.

Sorry that I can't help further.

9

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