kForth serial port interface update

The RS232 serial port interface for kForth (-32/64 for Linux) has been updated to be able to provide user access to the modem bits e.g. DSR, CTS etc.
https://github.com/mynenik/kForth-64/blob/master/forth-src/serial.4th
One use is to use the serial port for reading an external switch. Code example follows for a two-position switch. In my application, I have a nice big bright red gamer spring-loaded push button switch, which I want to use to begin an audio recording for recording a practice take on guitar -- it's not easy to access the keyboard with guitar in hand, positioned in front of a microphone (the recording code is actually a Forth script which makes use of the ALSA commands arecord, aplay etc. but more on that at a later date).
--
Krishna Myneni
=== begin rs232-switch.4th ===
\ rs232-switch.4th
\
\ External push button switch connected to serial port
\ via RTS/CTS lines may be queried with this code to
\ find out button status (pushed in/closed or open).
\ This is useful in applications when you can't access
\ the keyboard easily.
\
\  PC Serial Port (DB9 connector)
\
\   1  DCD  <--           ==============
\   2  RXD  <--            \ 1 2 3 4 5 /  ( male connector )
\   3  TXD  -->             \ 6 7 8 9 /
\   4  DTR  -->              =========
\   5  GND
\   6  DSR  <--           SW1 /==== SW3          ==== SW3
\   7  RTS  -->        -->===/              -->\
\   8  CTS  <--        <--1K---==== SW2  <--1K--\==== SW2
\   9  RI   <--              (open/OFF)         (closed/ON)
\
\ There is a 1K resistor in series with pin SW2 on the switch.
\
\ To use:
\   1. Open the com port (COM1 is shown in this example)
\   2. Enable the switch using RAISE-RTS
\   3. Query the switch using READ-SWITCH
\   4. Disable the switch using LOWER-RTS
\   5. Close the com port
\
include ans-words
include modules
include struct-200x
include struct-200x-ext
include strings
include serial
Also serial
base @
decimal
hex
20 constant CTS_LINE
decimal
variable com
: open-it  ( -- ior )
     COM1 ∋ serial open com !
     com @ 0> IF
       com @ c" 8N1" set-params
       com @ B57600 set-baud
       com @ ∋ serial flush
       0
     ELSE 1 THEN
     com @ lower-rts
;
: close-it ( -- ior )  com @ ∋ serial close ;
\ Return true if switch is closed (ON), false otherwise
: read-switch ( -- bOn )
     com @ get-modem-bits CTS_LINE and 0<> ;
\ More thorough debugging can be perfomed with TEST-SWITCH
false value user-abort?
: test-switch ( -- )
     open-it ABORT" Unable to open serial port!"
     read-switch IF
       cr ." CTS is raised. Ensure switch is OFF and try again."
       cr close-it drop EXIT
     THEN
     cr ." Press a key on the keyboard to raise RTS."
     BEGIN key? UNTIL  key drop
     com @ raise-rts
     cr ." Press and hold the push-button switch."
     cr ." If there is no effect, press Esc to exit the test." cr
     false to user-abort?
     BEGIN
       key? dup IF
         key 27 = and dup
         IF true to user-abort? THEN
       THEN
       0=
     WHILE
       read-switch 0=
     WHILE
     REPEAT
       cr ." CTS has been raised (switch is ON)."
       cr ." Please release the switch to OFF position."
       BEGIN
         1000 usleep
         read-switch 0=
       UNTIL
       cr ." CTS is low (switch is OFF)."
     THEN
     com @ lower-rts
     close-it drop
     user-abort? IF cr ." Test aborted by user!" cr THEN
;
cr cr .( Type 'TEST-SWITCH' to check operation of switch. ) cr
base !
=== end rs232-switch.4th ===