Megahertz , I would send the string " DEBUG $64" instead of "DEBUG 01100100 " What you are sending is a string of ascii 0's and 1's. I beleive the module is looking for a single HEX character equivalent value... This way you will always be sending 8 bits... And YES, the serial data presented by DEBUG is LSB first, just as in normal RS-232, assuming that is the format the module is looking for data to be presented...

Dave Purola,
N8NTA