Ta-da! Thanks @TrystanLea; I was compiling the two ino files in separate windows, rather than in the one window - I assumed that they were separate programs, rather than being two elements of the same sketch. Presumably the following warning after compiling is within tolerance? “Sketch uses 16082 bytes (49%) of program storage space. Maximum is 32256 bytes.
Global variables use 1732 bytes (84%) of dynamic memory, leaving 316 bytes for local variables. Maximum is 2048 bytes.
Low memory available, stability problems may occur.”
