You have multiple mistakes in your code. You should read up on "if statement".
You should have double equal in while and if statement like if (iteration==1).
I understand your intent. I have software library that does the input you want but will need modification to run on your shield. I feel like most of us have become free tech support for this dfrobot company. They produce cheap and low quality designs and leave the arduino forum to support them. I am not interested in modifying my library to support their product, would just help them such more money and burden us more. Be my guest if you want to modify it though.
