first byte choked when reading again after a read time-out

[volkers]

Hi, I run into following problem (on Windows 10, sbcl):
After a timeout when reading, the next byte/character is missing when reading the next bytes. I made a simple test with a loopback device:

(ql:quickload 'cserial-port)
(defvar *device* "COM3")
(defvar *serial-stream* nil)


(defun open-serial-stream ()
  (unless *serial-stream*
    (setq *serial-stream*
          (cserial-port:open-serial *device*
                                    ;;:baud-rate 38400
                                    :baud-rate 9600
                                    :data-bits 8
                                    :stop-bits 1
                                    :parity :none)
          )))

(defun close-serial-stream ()
  (when *serial-stream*
    (cserial-port:close-serial *serial-stream*)
    (setq *serial-stream* nil)))

(defun send-x (b)
  (cserial-port:write-serial-byte b *serial-stream*))

(defun read-x ()
  (handler-case 
      (cserial-port:read-serial-byte *serial-stream* :timeout-ms 10)
    (CSERIAL-PORT:TIMEOUT-ERROR () nil)))


;; test

(open-serial-stream)
(pprint "Write 117 followed by 118 and read them back")
(send-x 117)
(send-x 118)
(sleep 0.01)
(pprint (read-x))
(pprint (read-x))

(pprint "Read again, timeout:")
(pprint (read-x))

(sleep 0.01)

(pprint "Write 117 followed by 118 and read them back")
(send-x 117)
(send-x 118)
(sleep 0.01)
(pprint (read-x))
(pprint "first byte missing!")
;; (pprint (read-x))

(pprint "Write 117 followed by 118 and read them back")
(send-x 117)
(send-x 118)
(sleep 0.5)
(pprint (read-x))
(pprint (read-x))
(pprint "Works correctly again")

(close-serial-stream)

Following output:

"Write 117 followed by 118"
117
118
"Read again, timeout:"
NIL
"Write 117 followed by 118"
118
"first byte missing!"
"Write 117 followed by 118"
117
118
"Works correctly again"