class GroveUltrasonicRanger:
def __init__(self, sig_pin, unit=1.0, timeout=1.0):
self.unit = unit
self.timeout = timeout
self.echo = PulseIn(sig_pin)
self.echo.pause()
self.echo.clear()
def __enter__(self):
"""Allows for use in context managers."""
return self
def __exit__(self, exc_type, exc_val, exc_tb):
"""Automatically de-initialize after a context manager."""
self.deinit()
def deinit(self):
"""De-initialize the sig pin."""
self.echo.deinit()
def dist_two_wire(self):
self.echo.clear() # Discard any previous pulse values
time.sleep(0.00001) # 10 micro seconds 10/1000/1000
timeout = time.monotonic()
self.echo.resume(20)
while len(self.echo) == 0:
# Wait for a pulse
if (time.monotonic() - timeout) > self.timeout:
self.echo.pause()
return -1
self.echo.pause()
if self.echo[0] == 65535:
return -1
return (self.echo[0] / 2) / (291 / 10)
def distance(self):
return self.dist_two_wire()
class DHTBase:
"""base support for DHT11 and DHT22 devices
:param bool dht11: True if device is DHT11, otherwise DHT22.
:param ~board.Pin pin: digital pin used for communication
:param int trig_wait: length of time to hold trigger in LOW state (microseconds)
:param bool use_pulseio: False to force bitbang when pulseio available (only with Blinka)
"""
__hiLevel = 51
def __init__(self,
dht11: bool,
pin: Pin,
trig_wait: int,
use_pulseio: bool,
*,
max_pulses: int = 81):
self._dht11 = dht11
self._pin = pin
self._trig_wait = trig_wait
self._max_pulses = max_pulses
self._last_called = 0
self._humidity = None
self._temperature = None
self._use_pulseio = use_pulseio
if "Linux" not in uname() and not self._use_pulseio:
raise Exception(
"Bitbanging is not supported when using CircuitPython.")
# We don't use a context because linux-based systems are sluggish
# and we're better off having a running process
if self._use_pulseio:
self.pulse_in = PulseIn(self._pin,
maxlen=self._max_pulses,
idle_state=True)
self.pulse_in.pause()
def exit(self) -> None:
"""Cleans up the PulseIn process. Must be called explicitly"""
if self._use_pulseio:
print("De-initializing self.pulse_in")
self.pulse_in.deinit()
def _pulses_to_binary(self, pulses: array.array, start: int,
stop: int) -> int:
"""Takes pulses, a list of transition times, and converts
them to a 1's or 0's. The pulses array contains the transition times.
pulses starts with a low transition time followed by a high transistion time.
then a low followed by a high and so on. The low transition times are
ignored. Only the high transition times are used. If the high
transition time is greater than __hiLevel, that counts as a bit=1, if the
high transition time is less that __hiLevel, that counts as a bit=0.
start is the starting index in pulses to start converting
stop is the index to convert upto but not including
Returns an integer containing the converted 1 and 0 bits
"""
binary = 0
hi_sig = False
for bit_inx in range(start, stop):
if hi_sig:
bit = 0
if pulses[bit_inx] > self.__hiLevel:
bit = 1
binary = binary << 1 | bit
hi_sig = not hi_sig
return binary
def _get_pulses_pulseio(self) -> array.array:
"""_get_pulses implements the communication protocol for
DHT11 and DHT22 type devices. It sends a start signal
of a specific length and listens and measures the
return signal lengths.
return pulses (array.array uint16) contains alternating high and low
transition times starting with a low transition time. Normally
pulses will have 81 elements for the DHT11/22 type devices.
"""
pulses = array.array("H")
if self._use_pulseio:
# The DHT type device use a specialize 1-wire protocol
# The microprocessor first sends a LOW signal for a
# specific length of time. Then the device sends back a
# series HIGH and LOW signals. The length the HIGH signals
# represents the device values.
self.pulse_in.clear()
self.pulse_in.resume(self._trig_wait)
# loop until we get the return pulse we need or
# time out after 1/4 second
time.sleep(0.25)
self.pulse_in.pause()
while self.pulse_in:
pulses.append(self.pulse_in.popleft())
return pulses
def _get_pulses_bitbang(self) -> array.array:
"""_get_pulses implements the communication protcol for
DHT11 and DHT22 type devices. It sends a start signal
of a specific length and listens and measures the
return signal lengths.
return pulses (array.array uint16) contains alternating high and low
transition times starting with a low transition time. Normally
pulses will have 81 elements for the DHT11/22 type devices.
"""
pulses = array.array("H")
with DigitalInOut(self._pin) as dhtpin:
# we will bitbang if no pulsein capability
transitions = []
# Signal by setting pin high, then low, and releasing
dhtpin.direction = Direction.OUTPUT
dhtpin.value = True
time.sleep(0.1)
dhtpin.value = False
# Using the time to pull-down the line according to DHT Model
time.sleep(self._trig_wait / 1000000)
timestamp = time.monotonic() # take timestamp
dhtval = True # start with dht pin true because its pulled up
dhtpin.direction = Direction.INPUT
try:
dhtpin.pull = Pull.UP
# Catch the NotImplementedError raised because
# blinka.microcontroller.generic_linux.libgpiod_pin does not support
# internal pull resistors.
except NotImplementedError:
dhtpin.pull = None
while time.monotonic() - timestamp < 0.25:
if dhtval != dhtpin.value:
dhtval = not dhtval # we toggled
transitions.append(time.monotonic()) # save the timestamp
# convert transtions to microsecond delta pulses:
# use last 81 pulses
transition_start = max(1, len(transitions) - self._max_pulses)
for i in range(transition_start, len(transitions)):
pulses_micro_sec = int(1000000 *
(transitions[i] - transitions[i - 1]))
pulses.append(min(pulses_micro_sec, 65535))
return pulses
def measure(self) -> None:
"""measure runs the communications to the DHT11/22 type device.
if successful, the class properties temperature and humidity will
return the reading returned from the device.
Raises RuntimeError exception for checksum failure and for insufficient
data returned from the device (try again)
"""
delay_between_readings = 2 # 2 seconds per read according to datasheet
# Initiate new reading if this is the first call or if sufficient delay
# If delay not sufficient - return previous reading.
# This allows back to back access for temperature and humidity for same reading
if (self._last_called == 0 or
(time.monotonic() - self._last_called) > delay_between_readings):
self._last_called = time.monotonic()
new_temperature = 0
new_humidity = 0
if self._use_pulseio:
pulses = self._get_pulses_pulseio()
else:
pulses = self._get_pulses_bitbang()
# print(len(pulses), "pulses:", [x for x in pulses])
if len(pulses) < 10:
# Probably a connection issue!
raise RuntimeError("DHT sensor not found, check wiring")
if len(pulses) < 80:
# We got *some* data just not 81 bits
raise RuntimeError(
"A full buffer was not returned. Try again.")
buf = array.array("B")
for byte_start in range(0, 80, 16):
buf.append(
self._pulses_to_binary(pulses, byte_start,
byte_start + 16))
if self._dht11:
# humidity is 1 byte
new_humidity = buf[0]
# temperature is 1 byte
new_temperature = buf[2]
else:
# humidity is 2 bytes
new_humidity = ((buf[0] << 8) | buf[1]) / 10
# temperature is 2 bytes
# MSB is sign, bits 0-14 are magnitude)
new_temperature = (((buf[2] & 0x7F) << 8) | buf[3]) / 10
# set sign
if buf[2] & 0x80:
new_temperature = -new_temperature
# calc checksum
chk_sum = 0
for b in buf[0:4]:
chk_sum += b
# checksum is the last byte
if chk_sum & 0xFF != buf[4]:
# check sum failed to validate
raise RuntimeError("Checksum did not validate. Try again.")
if new_humidity < 0 or new_humidity > 100:
# We received unplausible data
raise RuntimeError("Received unplausible data. Try again.")
self._temperature = new_temperature
self._humidity = new_humidity
@property
def temperature(self) -> Union[int, float, None]:
"""temperature current reading. It makes sure a reading is available
Raises RuntimeError exception for checksum failure and for insufficient
data returned from the device (try again)
"""
self.measure()
return self._temperature
@property
def humidity(self) -> Union[int, float, None]:
"""humidity current reading. It makes sure a reading is available
Raises RuntimeError exception for checksum failure and for insufficient
data returned from the device (try again)
"""
self.measure()
return self._humidity
class HCSR04:
"""Control a HC-SR04 ultrasonic range sensor.
Example use:
::
with HCSR04(trig, echo) as sonar:
try:
while True:
print(sonar.dist_cm())
sleep(2)
except KeyboardInterrupt:
pass
"""
def __init__(self, trig_pin, echo_pin, timeout_sec=.1):
"""
:param trig_pin: The pin on the microcontroller that's connected to the
``Trig`` pin on the HC-SR04.
:type trig_pin: str or microcontroller.Pin
:param echo_pin: The pin on the microcontroller that's connected to the
``Echo`` pin on the HC-SR04.
:type echo_pin: str or microcontroller.Pin
:param float timeout_sec: Max seconds to wait for a response from the
sensor before assuming it isn't going to answer. Should *not* be
set to less than 0.05 seconds!
"""
if isinstance(trig_pin, str):
trig_pin = getattr(board, trig_pin)
if isinstance(echo_pin, str):
echo_pin = getattr(board, echo_pin)
self.dist_cm = self._dist_two_wire
self.timeout_sec = timeout_sec
self.trig = DigitalInOut(trig_pin)
self.trig.switch_to_output(value=False, drive_mode=DriveMode.PUSH_PULL)
self.echo = PulseIn(echo_pin)
self.echo.pause()
self.echo.clear()
def __enter__(self):
"""Allows for use in context managers."""
return self
def __exit__(self, exc_type, exc_val, exc_tb):
"""Automatically de-initialize after a context manager."""
self.deinit()
def deinit(self):
"""De-initialize the trigger and echo pins."""
self.trig.deinit()
self.echo.deinit()
def dist_cm(self):
"""Return the distance measured by the sensor in cm.
This is the function that will be called most often in user code. The
distance is calculated by timing a pulse from the sensor, indicating
how long between when the sensor sent out an ultrasonic signal and when
it bounced back and was received again.
If no signal is received, the return value will be ``-1``. This means
either the sensor was moving too fast to be pointing in the right
direction to pick up the ultrasonic signal when it bounced back (less
likely), or the object off of which the signal bounced is too far away
for the sensor to handle. In my experience, the sensor can detect
objects over 460 cm away.
:return: Distance in centimeters.
:rtype: float
"""
# This method only exists to make it easier to document. See either
# _dist_one_wire or _dist_two_wire for the actual implementation. One
# of those two methods will be assigned to be used in place of this
# method on instantiation.
pass
def _dist_two_wire(self):
self.echo.clear() # Discard any previous pulse values
self.trig.value = 1 # Set trig high
time.sleep(0.00001) # 10 micro seconds 10/1000/1000
self.trig.value = 0 # Set trig low
timeout = time.monotonic()
self.echo.resume()
while len(self.echo) == 0:
# Wait for a pulse
if (time.monotonic() - timeout) > self.timeout_sec:
self.echo.pause()
return -1
self.echo.pause()
if self.echo[0] == 65535:
return -1
return (self.echo[0] / 2) / (291 / 10)