I had the same problem, so in case you haven't figured it out yourself by now:
In the tutorial above with BT5R2 you need to run "make && make -C tools" (without the quotation marks) directly...
Type: Posts; User: jonathanlogitech; Keyword(s):
Re: Error: insmod: error inserting './com_on_air_cs.ko': -1 Invalid module format
I had the same problem, so in case you haven't figured it out yourself by now:
In the tutorial above with BT5R2 you need to run "make && make -C tools" (without the quotation marks) directly...