main.py

"""Program entry point"""

import serial as sr
import waiting as wt
import sys
import io

# Serial communication timeout in ms
SERIAL_TIMEOUT_MS = 1e4

# Messages for changing debugee clock speed
CLOCK_DOWN = "8\n"
CLOCK_UP = "1\n"

# Messages for toggling debugWIRE
DWIRE_ON = "+\n"
DWIRE_OFF = "-\n"

# Messages for entering debugging mode
ENTER_DEBUG_SESSION = "b\n"


class WayneProbeSession:
    def __init__(self, port: str, ostream: io.StringIO):
        """
        Bind a debugging session to a serial port

        port -- port of the Wayne probe
        ostream -- output stream for communication logs
        """

        self._port = port
        self._ostream = ostream

    def __enter__(self):
        """
        Open a serial communication to a Wayne probe and automatically start a debugging session
        """

        # Open a serial communication to the Wayne probe and wait until it is
        # up
        self._serial = sr.Serial(
            port=self._port,
            baudrate=115200,
            bytesize=8,
            parity=sr.PARITY_NONE,
            stopbits=sr.STOPBITS_ONE,
            timeout=self.SERIAL_TIMEOUT_MS,
        )
        wt.wait(
            lambda: self._serial.in_waiting > 0,
            timeout_seconds=(self.SERIAL_TIMEOUT_MS * 1e-3),
        )
        self._serial.read(self._serial.in_waiting)

        self._ostream.write(self._send(self.CLOCK_DOWN))
        self._ostream.write(self._send(self.DWIRE_ON))
        self._ostream.write(self._send(self.ENTER_DEBUG_SESSION))

        return self

    def __exit__(self, exception_type, value, traceback):
        """
        Restore debuggee configuration and close the serial communication
        """

        self._ostream.write(self._send("EXIT\n"))
        self._ostream.write(self._send(self.DWIRE_OFF))
        self._ostream.write(self._send(self.CLOCK_DOWN))
        self._serial.close()

    def next(self):
        """
        Reach next instruction

        return the Wayne probe response
        """

        return self._send("STEP\n")

    def _send(self, message: str):
        """
        Send a message to the Wayne probe and return the response
        """

        self._serial.write(message.encode())
        try:
            wt.wait(
                lambda: self._serial.in_waiting > 0,
                timeout_seconds=(self.SERIAL_TIMEOUT_MS * 1e-3),
            )
            return self._serial.read(self._serial.in_waiting).decode("ascii")
        except BaseException:
            return None


with WayneProbeSession("/dev/ttyUSB0", sys.stdout) as session:
    while True:
        input()
        print(session.next())