"""
LEGO Mindstorms EV3 direct commands - ultrasonic
"""
import struct
from .ev3 import EV3
from .constants import (
PORT_1,
PORT_2,
PORT_3,
PORT_4,
opInput_Device,
READY_RAW,
NXT_ULTRASONIC,
EV3_ULTRASONIC
)
from .functions import LCX, GVX
from .exceptions import SensorError, PortInUse
[docs]class Ultrasonic(EV3):
"""
controls a single ultrasonic sensor in cm mode
"""
def __init__(
self,
port: bytes,
*,
protocol: str = None,
host: str = None,
ev3_obj: EV3 = None,
verbosity=0
):
"""
Positional Arguments
port
port of ultrasonic sensor (PORT_1, PORT_2, PORT_3 or PORT_4)
Keyword only Arguments (either protocol and host or ev3_obj)
protocol
either ev3_dc.BLUETOOTH, ev3_dc.USB or ev3_dc.WIFI
host
mac-address of the LEGO EV3 (e.g. '00:16:53:42:2B:99')
ev3_obj
an existing EV3 object
(its already established connection will be used)
verbosity
level (0, 1, 2) of verbosity (prints on stdout).
"""
assert port in (PORT_1, PORT_2, PORT_3, PORT_4), "incorrect port"
self._port = port
super().__init__(
protocol=protocol,
host=host,
ev3_obj=ev3_obj,
verbosity=verbosity
)
if self._physical_ev3._introspection is None:
self._physical_ev3.introspection(verbosity)
if self.sensors_as_dict[self._port] not in (
NXT_ULTRASONIC,
EV3_ULTRASONIC
):
port_str = 'PORT_' + str(1 + struct.unpack("<B", self._port)[0])
raise SensorError('no ultrasonic connected at ' + port_str)
if self._physical_ev3._introspection["sensors"][self._port]['used_by'] is not None:
port_str = 'PORT_' + str(1 + struct.unpack("<B", self._port)[0])
host_str = self._physical_ev3._host
raise PortInUse(f'{port_str} of {host_str} already in use')
def __str__(self):
"""description of the object in a str context"""
type_str = (
'EV3_ULTRASONIC'
if self.sensor_type == EV3_ULTRASONIC
else 'NXT_ULTRASONIC'
)
port_str = 'PORT_' + str(1 + struct.unpack("<B", self._port)[0])
return ' '.join((
type_str,
f'at {port_str}',
f'of {super().__str__()}'
))
def __del__(self):
"""
handle specific logic for deletion
"""
if self._physical_ev3 is not None:
self._physical_ev3._introspection["sensors"][self._port]['used_by'] = None
super().__del__()
def __exit__(self, exc_type, exc_value, exc_traceback):
"""
handle specific logic when exit with block
"""
self._physical_ev3._introspection["sensors"][self._port]['used_by'] = None
super().__exit__(exc_type, exc_value, exc_traceback)
@property
def port(self) -> bytes:
"""
port, where sensor is connected (PORT_1, PORT_2, PORT_3 or PORT_4)
"""
return self._port
@property
def sensor_type(self) -> int:
"""
type of sensor
"""
return self.sensors_as_dict[self._port]
@property
def distance(self) -> float:
"""
distance [m] ahead, where the sensor detected something
distances are between 0.01 and 2.55 m. None stands for 'seen nothing'
"""
reply = self.send_direct_cmd(
b''.join((
opInput_Device, # operation
READY_RAW, # CMD
LCX(0), # LAYER
self._port, # NO
LCX(5), # TYPE
LCX(0), # MODE (cm)
LCX(1), # VALUES
GVX(0) # VALUE1 (output)
)),
global_mem=4
)
dist = struct.unpack('<i', reply)[0]
if dist == 255:
return None
return float(dist/ 100)