scanf problem with RDI on Cygwin?

[XUE]

hi all,
 
 Insight does have a scanf problem with RDI on Cygwin.  
 
windows 2000,
cygwin 1.3.2,
insight 5.5.1,
When this GDB was configured as "--host=i686-pc-cygwin --target=arm-elf",
I run arm-elf-gdb with -nw, use the target ARM Angel/Serial, com1 to connect
to the ARM Evaluator-7T target board.(target rdi com1 57600), I have scanf()
working great.
but When I try to run Insight GUI, I can't use scanf to get the input from
the cygwin prompt or the console window of Insight (View/Console) , the
scanf() always directly return -1.
 
Linux Mandrake release 8.0,
insight 5.5.1,
While this GDB was configured as "i686-pc-linux-gnu --target=arm-elf",
I run Insight GUI(target rdi /dev/ttyS0 57600), I can input from the linux
termianl running "arm-elf-gdb". 
 
Is this a cygwin question?
How can I just use scanf to get the input on Cygwin?
 
 Thanks & best regards