(...) Did you set the correct permissions for the serial ports (normally they're only accessible by root under Linux) Do a chmod 777 for /dev/ttyS0 (24 years ago, 3-Nov-00, to lugnet.robotics.rcx.nqc)
(...) Umm.. note the prompt ;)) I'd done an su root before testing to avoid permissions problems. This seems like a problem with nqc on LinuxPPC 3Q99, but I can't understand quite what it is as the tower obviously works - the green light is visible (...) (24 years ago, 3-Nov-00, to lugnet.robotics.rcx.nqc)
(...) Have you tried using setserial to set the correct baud rate and other options? Also note that when using "su" it sometimes doesn't take over all the settings from the user account that you used to log on. Perhaps the sudo command would work (...) (24 years ago, 4-Nov-00, to lugnet.robotics.rcx.nqc)