On Tue, 2002-09-10 at 20:39, LEE, Yui-wah (Clement) wrote: > When running the command "setserial /dev/usb/ttyUSB0", I got the error > "Invalid Argument". (Strace shown that it was an ioctl() failed with > EINVAL).
This alone is not all that dangerous. Not all serial drivers support all serial ioctls (or all combinations of parameters). The driver is supposed to reject everything that it can't do, and that appears to be the case. > When running minicom, I got no response from the modem in > the phone (I was using the speeds of 57600 and 230400 and various > other speeds). However, in some occasions I did see some garbage > echoed back (this happened when I switched from 230400 to 57600 baud > rate). a) High baud rates are hard to implement without a custom crystal. The divider becomes so small that you start getting high clock skew within the frame time. Refrain from anything above 38.4 kbps. b) The FTDI chip does not tell anyone (on its serial side) what baud rate is set. If the modem hardware connected to it can't properly sense the baud rate then it won't work. My guess is that the FT8U232AM is just fine, but the modem can't figure out what it is getting from the USB-Serial converter. Maybe you are expected to work on a fixed baud rate; maybe there should be some synchronization sequence (like CR few times)... Dmitri
signature.asc
Description: This is a digitally signed message part
