Andy 
I have a program which is called from rcS at startup. It utilises ttySAC3. This program runs fine on a Mini6410, and has done for years. If I run it from rcS on a Mini210S then ttySAC3 receive works but the transmit does not. If I then kill the process and manually start it then the data that should have been sent is transmitted as well as the data I have just transmitted.. The command line that I have always used is :- /bin/stty -F /dev/ttySAC3 raw -echo speed 9600 If I add -crtscts it makes no difference. I am using Linux from the Mini210s-2012081 disk. I will try the 20121228 one if I can every get it to download. Any ideas gratefully accepted ;) Thanks Andy.