(load-extension "ser-ext.so")
; above should show: 
; "extension includes: open-tty write-tty read-tty close-tty"

(define (o) (open-tty "/dev/tty.USA19H181P1.1" 9600))
(define (c) (close-tty))

;; Keyspan: (o) should make green light solid (ie, stop blinking)
;; Keyspan: (c) should make green light blink again
;; (t "text to loop back") should loop back text if 
;;   tx & rx pins are connected
;; (t integer) should send only that character (eg, 3 is cntl-c)
  
 
(define  (t text-to-loop-back) 
  ; multiple reads prove destructive behavior
  (list (read-tty)
        (write-tty text-to-loop-back)
        (sleep 0.1)
        (read-tty)
        (read-tty)))