Global Arrays read as Zero
Since addr_t is a character type, I suspect Serial.print() is trying to output the ASCII character representation of your two values. ASCII codes 0x10 and 0x02 are non-printing characters, so it might just be outputting 0's for lack of anything better to do.

To output the data as actual numbers, try casting them to integers:


Serial.print( static_cast&lt;unsigned int&gt;(childAddr[0]) );
Serial.print( static_cast&lt;unsigned int&gt;(childAddr[1]) );