Roboteksperimentarium/robot.py

# Arlo Robot Controller

from time import sleep
import serial

class Robot(object):
    """
    Defines the Arlo robot API

    DISCLAIMER: This code does not contain error checking - it is the
    responsibility of the caller to ensure proper parameters and not to send
    commands to the Arduino too frequently (give it time to process the command
    by adding a short sleep wait statement). Failure to do some may lead to
    strange robot behaviour.

    In case you experience trouble - consider using only commands that do not
    use the wheel encoders.
    """
    def __init__(self, port = '/dev/ttyACM0'):
        """
        The constructor port parameter can be changed from default value if you
        want to control the robot directly from your labtop (instead of from
        the on-board raspberry pi). The value of port should point to the USB
        port on which the robot Arduino is connected.
        """
        self.port = port

        # 1 sec. timeout, wait until data is received or until timeout
        # self.serialRead = serial.Serial(self.port,9600, timeout=1)

        # No timeout, wait forever or until data is received
        self.serial_read = serial.Serial(self.port,9600, timeout=None)

        # Wait if serial port is not open yet
        while not self.serial_read.isOpen():
            sleep(1)

        print("Waiting for serial port connection ...")
        sleep(2)

        print("Running ...")

    def __del__(self):
        print("Shutting down the robot ...")

        sleep(0.05)
        print(self.stop())
        sleep(0.1)

        cmd='k\n'
        print((self.send_command(cmd)))
        self.serial_read.close()

    def send_command(self, cmd, sleep_ms=0.0):
        """Sends a command to the Arduino robot controller"""
        self.serial_read.write(cmd.encode('ascii'))
        sleep(sleep_ms)
        str_val=self.serial_read.readline()
        return str_val


    def _power_checker(self, power):
        """
        Checks if a power value is in the set {0, [40;127]}.
        This is an internal utility function.
        """
        return  (power == 0) or (power >=40 and power <=127)

    def go_diff(self, power_left, power_right, dir_left, dir_right):
        """
        Start left motor with motor power powerLeft (in {0, [40;127]} and the
        numbers must be integer) and direction dirLeft (0=reverse, 1=forward)
        and right motor with motor power powerRight (in {0, [40;127]} and the
        numbers must be integer) and direction dirRight (0=reverse, 1=forward).

        The Arlo robot may blow a fuse if you run the motors at less than 40 in
        motor power, therefore choose either power = 0 or 40 < power <= 127.

        This does NOT use wheel encoders.
        """

        if (
            (not self._power_checker(power_left)) or
            (not self._power_checker(power_right))
        ):
            print("WARNING: Read the docstring of Robot.go_diff()!")
            return ""
        else:
            pl_int = int(power_left)
            pr_int = int(power_right)
            dl_int = int(dir_left)
            dr_int = int(dir_right)
            cmd = f"d{pl_int},{pr_int},{dl_int},{dr_int}\n"
            return self.send_command(cmd)


    def stop(self):
        """
        Send a stop command to stop motors. Sets the motor power on both wheels
        to zero.

        This does NOT use wheel encoders.
        """
        cmd='s\n'
        return self.send_command(cmd)



    def read_sensor(self, sensorid):
        """
        Send a read sensor command with sensorid and return sensor value.

        Will return -1, if error occurs.
        """
        cmd=str(sensorid) + '\n'
        str_val=self.send_command(cmd)
        if len(str_val) > 0:
            return int(str_val)
        else:
            return -1

    def read_front_ping_sensor(self):
        """
        Read the front sonar ping sensor and return the measured range in
        milimeters [mm].
        """
        return self.read_sensor(0)

    def read_back_ping_sensor(self):
        """
        Read the back sonar ping sensor and return the measured range in
        milimeters [mm].
        """
        return self.read_sensor(1)

    def read_left_ping_sensor(self):
        """
        Read the left sonar ping sensor and return the measured range in
        milimeters [mm].
        """
        return self.read_sensor(2)

    def read_right_ping_sensor(self):
        """
        Read the right sonar ping sensor and return the measured range in
        milimeters [mm].
        """
        return self.read_sensor(3)


    def read_left_wheel_encoder(self):
        """
        Reads the left wheel encoder counts since last reset_encoder_counts
        command.

        The encoder has 144 counts for one complete wheel revolution.
        """
        cmd='e0\n'
        return self.send_command(cmd, 0.045)

    def read_right_wheel_encoder(self):
        """
        Reads the right wheel encoder counts since last clear
        reset_encoder_counts command.

        The encoder has 144 counts for one complete wheel revolution.
        """
        cmd='e1\n'
        return self.send_command(cmd, 0.045)

    def reset_encoder_counts(self):
        """Reset the wheel encoder counts."""
        cmd='c\n'
        return self.send_command(cmd)