How to convert a std::array to a std::vector?

You can use the constructor of std::vector taking iterators.

Constructs the container with the contents of the range [first, last).

e.g.

std::array<char,10> myData = {0,1,2,3,4,5,6,7,8,9};
std::vector<char> myvector(myData.begin(), myData.end());

Just for variety:

std::vector<char> myvector(std::begin(myData), std::end(myData);