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By shfitz
I'm using an Arduino Ethernet shield to poll a php page for changes. It works fine.

I also have a SM5100B shield. I've gotten it to send and receive texts.

Now, I'd like to have them to work together. The Ethernet shield gets an update from the web, the SM5100B sends a text. But, soon as I pop on the GSM shield, the ethernet no longer works. I can still connect to the cellular network.

When stacking the shields, and commenting out any relevant NewSoftSerial code, the ethernet connection still will not work.

I can't find any reason why this is happening. Any clues?

I missed the part where the two shields use Pin2 on the Arduino when the GSM module is using the NewSoftSerial library.

So, if I switch it to hardware serial, how would I go about monitoring this for debugging purposes?

Or, would it be possible to use a different set of pins for soft rx/tx?
By shfitz
Found a solution :)

I bent up pin2 on the cell shield and made a jumper to pin 4.

Changed the NewSoftSerial code to this :
NewSoftSerial cell(4,3);

and I placed the cell shield on an extra set of make/female headers so it rests on top of the ethernet shield (which is typically too tall for other shields to sit on top).