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# https://www.dexterindustries.com
#
# Copyright (c) 2018 Dexter Industries
# Released under the MIT license (http://choosealicense.com/licenses/mit/).
# For more information see https://github.com/DexterInd/DI_Sensors/blob/master/LICENSE.md
#
from di_sensors.easy_mutex import ifMutexAcquire, ifMutexRelease
import time
from di_sensors import distance_sensor
class EasyDistanceSensor(distance_sensor.DistanceSensor):
"""
Class for the `Distance Sensor`_ device.
This class compared to :py:class:`~di_sensors.distance_sensor.DistanceSensor` uses mutexes that allows a given
object to be accessed simultaneously from multiple threads/processes.
Apart from this difference, there may also be functions that are more user-friendly than the latter.
"""
def __init__(self, port="I2C", use_mutex=False):
"""
Creates a :py:class:`~easygopigo3.EasyDistanceSensor` object which can be used for interfacing with a `distance sensor`_.
:param string bus = ``"I2C"``: the bus for the sensor. For the GoPiGo3, options also include ``"GPG3_AD1"`` and ``"GPG3_AD2"``.
:param bool use_mutex = False: When using multiple threads/processes that access the same resource/device, mutexes should be enabled. Check the :ref:`hardware specs <hardware-interface-section>` for more information about the ports.
:raises ~exceptions.OSError: When the distance sensor is not connected to the designated bus/port, where in this case it must be ``"I2C"``. Most probably, this means the distance sensor is not connected at all.
To see where the ports are located on the `GoPiGo3`_ robot, please take a look at the following diagram: :ref:`hardware-ports-section`.
"""
self.descriptor = "Distance Sensor"
self.use_mutex = use_mutex
# let's be kind to the user who may get confused between ports and buses
# let's allow for all of them
possible_ports = { "I2C" : "RPI_1SW",
"AD1" : "GPG3_AD1",
"AD2" : "GPG3_AD2",
"RPI_1SW": "RPI_1SW",
"RPI_1" : "RPI_1",
"RPI_1HW" : "RPI_1", # doesn't really exist but can be a reflex for some users as we do have RPI_1SW
"GPG3_AD1": "GPG3_AD1",
"GPG3_AD2": "GPG3_AD2"}
port = port.upper() # force to uppercase
# switch quietly to default value if we receive gibberish
if port in possible_ports.keys():
bus = possible_ports[port]
else:
bus = "RPI_1SW"
ifMutexAcquire(self.use_mutex)
try:
distance_sensor.DistanceSensor.__init__(self, bus=bus)
except Exception as e:
# remove print so that it doesn't show when starting Scratch
# print("Distance Sensor init: {}".format(e))
raise
finally:
ifMutexRelease(self.use_mutex)
# Returns the values in cms
def read_mm(self):
"""
Reads the distance in millimeters.
:returns: Distance from target in millimeters.
:rtype: int
.. note::
1. Sensor's range is **5-2300** millimeters.
2. When the values are out of the range, it returns **3000**.
"""
# 8190 is what the sensor sends when it's out of range
# we're just setting a default value
mm = 8190
readings = []
attempt = 0
# try 3 times to have a reading that is
# smaller than 8m or bigger than 5 mm.
# if sensor insists on that value, then pass it on
while (mm > 8000 or mm < 5) and attempt < 3:
ifMutexAcquire(self.use_mutex)
try:
mm = self.read_range_single()
except Exception as e:
print(e)
mm = 0
finally:
ifMutexRelease(self.use_mutex)
attempt = attempt + 1
time.sleep(0.001)
# add the reading to our last 3 readings
# a 0 value is possible when sensor is not found
if (mm < 8000 and mm > 5) or mm == 0:
readings.append(mm)
if len(readings) > 3:
readings.pop(0)
# calculate an average and limit it to 5 > X > 3000
if len(readings) > 1: # avoid division by 0
mm = round(sum(readings) / float(len(readings)))
if mm > 3000:
mm = 3000
return mm
def read(self):
"""
Reads the distance in centimeters.
:returns: Distance from target in centimeters.
:rtype: int
.. note::
1. Sensor's range is **0-230** centimeters.
2. When the values are out of the range, it returns **300**.
"""
cm = self.read_mm()//10
return (cm)
def read_inches(self):
"""
Reads the distance in inches.
:returns: Distance from target in inches.
:rtype: float with one decimal
.. note::
1. Sensor's range is **0-90** inches.
2. Anything that's bigger than **90** inches is returned when the sensor can't detect any target/surface.
"""
cm = self.read()
return round(cm / 2.54, 1)
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