From: krishna.myneni@ccreweb.org   
      
   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 ===   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)