Reads a character from a serial port.
read-serial-port-char serial-port &optional timeout-error-p timeout-char => char
A serial-port object.
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 signaled, otherwise timeout-char is returned. The default value of timeout-error-p is
LispWorks User Guide and Reference Manual - 20 Sep 2017