The function read-serial-port-char reads and returns a character from the serial port associated with serial-port .
A timeout will occur if the character is not available before the read timeout (as specified by values given when the serial port was opened by open-serial-port).
When a timeout occurs, if
timeout-error-p
is non-nil, then an error of type
serial-port-timeout
is signalled, otherwise
timeout-char
is returned. The default value of
timeout-error-p
is
t
.