A quick reply :-) I can now exchange some data between then Sharp and the VICE. For that, you must:
On the PC - Give authority to access the port in read and write (for me: /dev/ttyUSB0) - Set the speed and parity (1200,N,8) of the port. I use putty to set and test the connection. I - Launch VICE and specify the name of the com port. I must launch it in command line, because there is a filter in the "open" windows. Thus, the command is "x128 -rsdev1 /dev/ttyUSB0" - In VICE, go to the menu settings/RS232 settings - set the serial1 device to 1200 - set Userport RS232 emulation - set the baud rate to 1200 - ensure the device for emulation is the serail1 device.
Now, everything work quite fine in both receiving and sending data.