Description：I was using board K60n512.I want to use the serial port to read data,But I find it has some problems.when I use to read
data from serial port,it blocks at there,until it has recevied data from serial prot.when I change the open_flages:fopen("ttyf:",(pointer)IO_SERIAL_RAW_IO | IO_SERIAL_NON_BLOCKING)，but it seems doesn‘t work.it blocks until it recevied some data.
I use the primitve libraries and configuration.and test the com ttya to ttyf
I find that ttya,ttyb,ttyc,ttye can achieve the NON_BLOCKING function by using the IO_SERIAL_NON_BLOCK mode,the othesrs doesn't.
I find that the "#define BSPCFG_ENABLE_TTYD 1" and "#define BSPCFG_ENABLE_TTYF 1" in the user_config.h file.
FILE_PTR serial_f=fopen("ttyf:",(pointer)(IO_SERIAL_RAW_IO | IO_SERIAL_NON_BLOCKING));
fgetc(serial_fd);//if doesn't have data,it will block at here
I don't konw why,it puzzled me for a long time.