This is the Edison forum and your question is related to the Galileo Board. I've checked that you already posted this question here: Intel galileo Serial1.read problem...... and you received a suggestion as well. Please check your original post in Galileo forum.
It is very likely you can NOT give 5V to Galileo Gen 2 board. It has on board voltage regulators and they go crazy if you supply low voltage. Definitely not 5V.
I tried 9 V input and board power regulator section get really warm which I can not explain.