class Phys(object):
"""
Physical Connection Object: interacts with the Arduino device.
"""
# pylint: disable=abstract-class-not-used
__metaclass__ = abc.ABCMeta
_imports = {}
_arguments = {}
_message_id = 0
_SIGNATURE = ['\xaa', '\x55']
def __init__(self):
"""
Abstraction of the HW layer.
"""
self._signature = MappedBuffer(fields=(
{"first_byte": "B"},
{"second_byte": "B"},
))
self._signature.first_byte = ord(self._SIGNATURE[0])
self._signature.second_byte = ord(self._SIGNATURE[1])
self._header = MappedBuffer(fields=(
{"message_len": "B"},
{"message_id": "B"},
))
self._payload = []
self._checksum = MappedBuffer(fields=(
{"checksum": "B"},
))
self._deadline = None
def new(self):
"""
Prepares for transmitting a new message.
"""
self._payload = []
self._message_id += 1
@classmethod
def prepare_arguments(cls):
"""
Function providing a list of arguments configurations.
Each entry will be loaded into ArgumentParser.add_argument
The default dictionary - cls._arguments - is empty.
"""
return cls._arguments.values(), cls._imports
@abc.abstractmethod
def _test_connection(self):
"""
Checks that the connection is established and functioning.
"""
@abc.abstractmethod
def _chars_available(self):
"""
Returns the number of charaters that can be read.
"""
@abc.abstractmethod
def _read_char(self):
"""
Read a char from the physical layer.
"""
@abc.abstractmethod
def _write_char(self, character):
"""
Write a char to the physical layer.
"""
@abc.abstractmethod
def _flush(self):
"""
Waits untill all the data is written.
"""
@abc.abstractmethod
def close(self):
"""
Terminates the connection.
"""
def _calculate_deadline(self, timeout_ms):
"""
Defines the deadline for the completion of the current
TX or RX operation.
"""
self._deadline = datetime.datetime.now() + \
datetime.timedelta(milliseconds=timeout_ms)
def _read_char_with_timeout(self):
"""
As the name suggests, either a chracter is received from the Arduino,
or the function will wait till the timeout expires.
"""
while datetime.datetime.now() < self._deadline:
if self._chars_available() > 0:
return self._read_char()
return False
def _hook_message_signature(self):
"""
Tries to identify the message signature, till
either it finds it, or the allotted time runs out.
"""
while True:
new_char = self._read_char_with_timeout()
while new_char == self._SIGNATURE[0]:
new_char = self._read_char_with_timeout()
if new_char == self._SIGNATURE[1]:
return True
if new_char is False:
return False
def _receive_buffer(self, size):
"""
Reads and stores "size" characters.
"""
receive_buffer = []
while datetime.datetime.now() < self._deadline:
if self._chars_available() > 0:
receive_buffer.append(self._read_char())
if len(receive_buffer) == size:
return receive_buffer
print "Timeout"
return []
def receive_message(self, timeout_ms=500):
"""
Receives a message and stops either when the message is
complete or when the allotted time expires, whichever
comes first.
"""
self._calculate_deadline(timeout_ms=timeout_ms)
if self._hook_message_signature() is False:
logging.info("Failed to obtain message signature "
"within allotted time")
return False
logging.debug("Got message signature.")
header = self._receive_buffer(size=self._header.buffer_length)
if header == []:
logging.info("Failed to obtain message header "
"within allotted time")
return False
logging.debug("Got message header.")
self._header.unpack(packed_data="".join(header))
payload_len = \
self._header.message_len - \
self._signature.buffer_length - \
self._header.buffer_length - \
self._checksum.buffer_length
if payload_len is not 0:
self._payload = self._receive_buffer(size=payload_len)
if self._payload == []:
logging.info("Failed to obtain message payload "
"within allotted time")
return False
logging.debug("Got message payload.")
for _ in self._payload:
logging.debug("payload {0}".format(binascii.hexlify(_)))
else:
logging.debug("Got empty message without payload.")
self._payload = []
checksum = self._receive_buffer(size=self._checksum.buffer_length)
if checksum == []:
logging.info("Failed to obtain message checksum "
"within allotted time")
return False
logging.debug("Got message checksum.")
self._checksum.unpack(packed_data="".join(checksum))
calculated_checksum = \
MappedBuffer.calculate_checksum(
[self._SIGNATURE[0], self._SIGNATURE[1],
self._header.buffer_checksum,
MappedBuffer.calculate_checksum(self._payload)])
if self._checksum.checksum == calculated_checksum:
logging.info("RX: id = {0}\t\tpayload = {1}".
format(self._header.message_id, self._payload))
logging.debug("Checksum verification successful.")
return True
else:
logging.info("Checksum verification failed:\n" +
"Received = {0}\n".format(self._checksum.checksum) +
"Calculated = {0}".format(calculated_checksum))
return False
def transmit_message(self, payload=""):
"""
Transmits a message
"""
self._message_id = (self._message_id + 1) % 256
self._header.message_len = \
self._signature.buffer_length + \
self._header.buffer_length + \
len(payload) + \
self._checksum.buffer_length
self._header.message_id = self._message_id
message = self._signature.pack() + self._header.pack() + payload
self._checksum.checksum = MappedBuffer.calculate_checksum(message)
message = message + self._checksum.pack()
logging.info("TX {0}".format(binascii.hexlify(message)))
for character in message:
self._write_char(character)
self._flush()
def ping(self):
"""
Sends an empty message to the device and waits for an ACK
to arrive before the timeout.
"""
if self._test_connection() is False:
return False
self.transmit_message()
return self.receive_message()
class Phys(with_metaclass(abc.ABCMeta, object)):
"""
Physical Connection Object: interacts with the Arduino device.
"""
_imports = {}
_arguments = {}
_message_id = 0
_SIGNATURE = ['\xaa', '\x55']
def __init__(self):
"""
Abstraction of the HW layer.
"""
self._signature = MappedBuffer(fields=(
{
"first_byte": "B"
},
{
"second_byte": "B"
},
))
self._signature.first_byte = ord(self._SIGNATURE[0])
self._signature.second_byte = ord(self._SIGNATURE[1])
self._header = MappedBuffer(fields=(
{
"message_len": "B"
},
{
"message_id": "B"
},
))
self._payload = []
self._checksum = MappedBuffer(fields=({"checksum": "B"}, ))
self._deadline = None
def new(self):
"""
Prepares for transmitting a new message.
"""
self._payload = []
self._message_id += 1
@classmethod
def prepare_arguments(cls):
"""
Function providing a list of arguments configurations.
Each entry will be loaded into ArgumentParser.add_argument
The default dictionary - cls._arguments - is empty.
"""
return list(cls._arguments.values()), cls._imports
@abc.abstractmethod
def _test_connection(self):
"""
Checks that the connection is established and functioning.
"""
@abc.abstractmethod
def _chars_available(self):
"""
Returns the number of charaters that can be read.
"""
@abc.abstractmethod
def _read_char(self):
"""
Read a char from the physical layer.
"""
@abc.abstractmethod
def _write_char(self, character):
"""
Write a char to the physical layer.
"""
@abc.abstractmethod
def _flush(self):
"""
Waits untill all the data is written.
"""
@abc.abstractmethod
def close(self):
"""
Terminates the connection.
"""
def _calculate_deadline(self, timeout_ms):
"""
Defines the deadline for the completion of the current
TX or RX operation.
"""
self._deadline = datetime.datetime.now() + \
datetime.timedelta(milliseconds=timeout_ms)
def _read_char_with_timeout(self):
"""
As the name suggests, either a chracter is received from the Arduino,
or the function will wait till the timeout expires.
"""
while datetime.datetime.now() < self._deadline:
if self._chars_available() > 0:
return self._read_char()
return False
def _hook_message_signature(self):
"""
Tries to identify the message signature, till
either it finds it, or the allotted time runs out.
"""
while True:
new_char = self._read_char_with_timeout()
while new_char == self._SIGNATURE[0]:
new_char = self._read_char_with_timeout()
if new_char == self._SIGNATURE[1]:
return True
if new_char is False:
return False
def _receive_buffer(self, size):
"""
Reads and stores "size" characters.
"""
receive_buffer = []
while datetime.datetime.now() < self._deadline:
if self._chars_available() > 0:
receive_buffer.append(self._read_char())
if len(receive_buffer) == size:
return receive_buffer
logging.info("phys._receive_buffer timeout")
return []
def receive_message(self, timeout_ms=500):
"""
Receives a message and stops either when the message is
complete or when the allotted time expires, whichever
comes first.
"""
self._calculate_deadline(timeout_ms=timeout_ms)
if self._hook_message_signature() is False:
logging.info("Failed to obtain message signature "
"within allotted time")
return False
logging.debug("Got message signature.")
header = self._receive_buffer(size=self._header.buffer_length)
if header == []:
logging.info("Failed to obtain message header "
"within allotted time")
return False
logging.debug("Got message header.")
self._header.unpack(packed_data="".join(header))
payload_len = \
self._header.message_len - \
self._signature.buffer_length - \
self._header.buffer_length - \
self._checksum.buffer_length
if payload_len is not 0:
self._payload = self._receive_buffer(size=payload_len)
if self._payload == []:
logging.info("Failed to obtain message payload "
"within allotted time")
return False
logging.debug("Got message payload.")
for _ in self._payload:
logging.debug("payload {0}".format(binascii.hexlify(_)))
else:
logging.debug("Got empty message without payload.")
self._payload = []
checksum = self._receive_buffer(size=self._checksum.buffer_length)
if checksum == []:
logging.info("Failed to obtain message checksum "
"within allotted time")
return False
logging.debug("Got message checksum.")
self._checksum.unpack(packed_data="".join(checksum))
calculated_checksum = \
MappedBuffer.calculate_checksum(
[self._SIGNATURE[0], self._SIGNATURE[1],
self._header.buffer_checksum,
MappedBuffer.calculate_checksum(self._payload)])
if self._checksum.checksum == calculated_checksum:
logging.info("RX: id = {0}\t\tpayload = {1}".format(
self._header.message_id, self._payload))
logging.debug("Checksum verification successful.")
return True
else:
logging.info("Checksum verification failed:\n" +
"Received = {0}\n".format(self._checksum.checksum) +
"Calculated = {0}".format(calculated_checksum))
return False
def transmit_message(self, payload=""):
"""
Transmits a message
"""
self._message_id = (self._message_id + 1) % 256
self._header.message_len = \
self._signature.buffer_length + \
self._header.buffer_length + \
len(payload) + \
self._checksum.buffer_length
self._header.message_id = self._message_id
message = self._signature.pack() + self._header.pack() + payload
self._checksum.checksum = MappedBuffer.calculate_checksum(message)
message = message + self._checksum.pack()
logging.info("TX {0}".format(binascii.hexlify(message)))
for character in message:
#check for python version
if sys.version_info[0] == 2:
self._write_char(character)
elif sys.version_info[0] == 3:
self._write_char(chr(character).encode("Latin-1"))
self._flush()
def ping(self):
"""
Sends an empty message to the device and waits for an ACK
to arrive before the timeout.
"""
if self._test_connection() is False:
return False
self.transmit_message()
return self.receive_message()
