pl2303:

octave:6> s = serial (); # 8-N-1
octave:7> s
s = 3
octave:8> srl_write(s,"hello")
ans =  5
octave:9> char(srl_read (s,5))
ans = hello
octave:10> char(srl_read (s,15)) # Not a ring, buffer is empty
^Csrl_read: Interrupting...
ans = 
octave:11> srl_flush(s, 1)
octave:12> char(srl_read (s,5)) # Blocked, as buffer is empty
^Csrl_read: Interrupting...
ans = 
octave:13> srl_write(s,"hello")
ans =  5
octave:14> char(srl_read (s,5)) # Does not block, as there is data in the buffer
ans = hello
octave:15> srl_close(s)


FT232RL:

octave:16> s = serial (); # 8-N-1
octave:17> s
s = 3
octave:18> srl_write(s,"hello")
ans =  5
octave:19> char(srl_read (s,5))
ans = hello
octave:20> char(srl_read (s,15)) # Not a ring, buffer is empty
^Csrl_read: Interrupting...
ans = 
octave:21> srl_flush (s, 1)
octave:22> char(srl_read (s,5)) # Blocked, as buffer is empty
^Csrl_read: Interrupting...
ans = 
octave:23> srl_write(s,"hello")
ans =  5
octave:24> char(srl_read (s,5)) # Does not block, as there is data in the buffer
ans = hello
octave:25>