I want to stack Ethernet shield and USB host together with my Arduino MEGA 2560. Each of these shields works fine separately. Is it necessary to contact bootloader pins with each shield and arduino board? I have connected and tried, but the problem exists.

only one shield works fine at once.(always the sheild that directly connect to the Arduino board). How do I resolve this problem ? I want to work all 2 shields at once.

these are the sheilds I have used.

  1. Circuits At Home USB Host Shield v2.0
  2. Ethernet Shield v5.0

Thank you

2 Answers 2


Both shields are SPI devices, and both shields seem to be hard-wired to use D10 as the chip select line.

In order for you to use both shields at once you will have to either modify one of them or connect the shield via jumper wires.

You will need to change the chip select connection on one of the shields from D10 to some other pin that is not currently used, and then modify your software (or the library) accordingly.

  • Do I have to Modify D10 from one of the shields and as well as change the library? can't I resolve it just by changing the library.
    – TP Ap
    Commented Jul 22, 2015 at 14:25
  • You HAVE to somehow re-route D10 on one of the shields. You also HAVE to inform the software that it's no longer using D10 but some other pin. Some libraries provide the ability to pass the CS (or SS if you prefer) pin when constructing the object, and some are hard coded. If the former you just change the pin number in your sketch. If the latter then you need to change the pin number in the library itself.
    – Majenko
    Commented Jul 22, 2015 at 14:27

Also, I think that there is an hardware bug on the USB Master shield: IC3, the 3-state buffer which converts MISO to 5V, is always active... The enable pin of this 74LVC1G125 (pin 1) should be connected to the pin ss_3V3. Then you can stack this shield with another one.

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