Adding Bytes Together into a long long int...?

[MarkT]

@J-M-L

it's the same - both would do (assuming frame.buf[c] is a byte)

|= is better as the compiler can optimize this to a single byte operation, using += would require 64 add sequences to be generated.

Its vital that frame.buf is unsigned in either case, ie declared as an array of byte or uint8_t.