附上dun.h中的函数说明:
/*!
@param type_of_device dunlibDCE(Master) or dunlibDTE(Slave).
@param RI Pio Assignments for RI pin.
@param DTR Pio Assignments for DTR pin.
@param DCD Pio Assignments for DCD pin.
@param DSR Pio Assignments for DSR.
A DUN_INIT_CFM message will be returned on completion.
If a modem signalling pin is not connected, use DUN_NO_PIN.
*/