def from_frames(self, frames, datatype_crc=None):
# Ignore frame index for anonymous transfers since they can't be
# multi-frame
if frames[0].source_node_id:
for i, f in enumerate(frames):
if i != f.frame_index:
raise IndexError(("Frame index mismatch: expected {0}, " +
"got {1}").format(i, f.frame_index))
self.transfer_id = frames[0].transfer_id
self.transfer_priority = frames[0].transfer_priority
self.source_node_id = frames[0].source_node_id
self.data_type_id = frames[0].data_type_id
self.dest_node_id = frames[0].dest_node_id
self.payload = sum((f.payload for f in frames), bytearray())
self.request_not_response = frames[0].request_not_response
self.broadcast_not_unicast = frames[0].broadcast_not_unicast
# For a multi-frame transfer, validate the CRC and frame indexes
if len(frames) > 1:
transfer_crc = self.payload[0] + (self.payload[1] << 8)
self.payload = self.payload[2:]
crc = common.crc16_from_bytes(self.payload, initial=datatype_crc)
if crc != transfer_crc:
raise ValueError(("CRC mismatch: expected {0:x}, got {1:x} " +
"for payload {2!r} (DTID {3:d})").format(
crc, transfer_crc, self.payload,
self.data_type_id))
def to_frames(self):
out_frames = []
remaining_payload = self.payload
# Prepend the transfer CRC to the payload if the transfer requires
# multiple frames
if len(remaining_payload) > 7:
crc = common.crc16_from_bytes(self.payload,
initial=self.data_type_crc)
remaining_payload = bytearray([crc & 0xFF, crc >> 8
]) + remaining_payload
# Generate the frame sequence
tail = 0x20 # set toggle bit high so the first frame is emitted with it cleared
while True:
# Tail byte contains start-of-transfer, end-of-transfer, toggle, and Transfer ID
tail = ((0x80 if len(out_frames) == 0 else 0) |
(0x40 if len(remaining_payload) <= 7 else 0) |
((tail ^ 0x20) & 0x20) | (self.transfer_id & 0x1F))
out_frames.append(
Frame(message_id=self.message_id,
data=remaining_payload[0:7] + bchr(tail)))
remaining_payload = remaining_payload[7:]
if not remaining_payload:
break
return out_frames
def to_frames(self):
out_frames = []
remaining_payload = self.payload
# Prepend the transfer CRC to the payload if the transfer requires
# multiple frames
if len(remaining_payload) > 7:
crc = common.crc16_from_bytes(self.payload,
initial=self.data_type_crc)
remaining_payload = bytearray([crc & 0xFF, crc >> 8]) + remaining_payload
# Generate the frame sequence
tail = 0x20 # set toggle bit high so the first frame is emitted with it cleared
while True:
# Tail byte contains start-of-transfer, end-of-transfer, toggle, and Transfer ID
tail = ((0x80 if len(out_frames) == 0 else 0) |
(0x40 if len(remaining_payload) <= 7 else 0) |
((tail ^ 0x20) & 0x20) |
(self.transfer_id & 0x1F))
out_frames.append(Frame(message_id=self.message_id, data=remaining_payload[0:7] + bchr(tail)))
remaining_payload = remaining_payload[7:]
if not remaining_payload:
break
return out_frames
def from_frames(self, frames):
# Initialize transfer timestamps from the first frame
self.ts_monotonic = frames[0].ts_monotonic
self.ts_real = frames[0].ts_real
# Validate the flags in the tail byte
expected_toggle = 0
expected_transfer_id = frames[0].bytes[-1] & 0x1F
for idx, f in enumerate(frames):
tail = f.bytes[-1]
if (tail & 0x1F) != expected_transfer_id:
raise TransferError("Transfer ID {0} incorrect, expected {1}".format(tail & 0x1F, expected_transfer_id))
elif idx == 0 and not (tail & 0x80):
raise TransferError("Start of transmission not set on frame 0")
elif idx > 0 and tail & 0x80:
raise TransferError("Start of transmission set unexpectedly on frame {0}".format(idx))
elif idx == len(frames) - 1 and not (tail & 0x40):
raise TransferError("End of transmission not set on last frame")
elif idx < len(frames) - 1 and (tail & 0x40):
raise TransferError("End of transmission set unexpectedly on frame {0}".format(idx))
elif (tail & 0x20) != expected_toggle:
raise TransferError("Toggle bit value {0} incorrect on frame {1}".format(tail & 0x20, idx))
expected_toggle ^= 0x20
self.transfer_id = expected_transfer_id
self.message_id = frames[0].message_id
payload_bytes = bytearray(b''.join(bytes(f.bytes[0:-1]) for f in frames))
# Find the data type
if self.service_not_message:
kind = dsdl.CompoundType.KIND_SERVICE
else:
kind = dsdl.CompoundType.KIND_MESSAGE
datatype = uavcan.DATATYPES.get((self.data_type_id, kind))
if not datatype:
raise TransferError("Unrecognised {0} type ID {1}"
.format("service" if self.service_not_message else "message", self.data_type_id))
# For a multi-frame transfer, validate the CRC and frame indexes
if len(frames) > 1:
transfer_crc = payload_bytes[0] + (payload_bytes[1] << 8)
payload_bytes = payload_bytes[2:]
crc = common.crc16_from_bytes(payload_bytes, initial=datatype.base_crc)
if crc != transfer_crc:
raise TransferError("CRC mismatch: expected {0:x}, got {1:x} for payload {2!r} (DTID {3:d})"
.format(crc, transfer_crc, payload_bytes, self.data_type_id))
self.data_type_id = datatype.default_dtid
self.data_type_signature = datatype.get_data_type_signature()
self.data_type_crc = datatype.base_crc
if self.service_not_message:
self.payload = datatype(_mode="request" if self.request_not_response else "response")
else:
self.payload = datatype()
# noinspection PyProtectedMember
self.payload._unpack(bits_from_bytes(payload_bytes))
def to_frames(self, datatype_crc=None):
# Broadcast frames support up to 8 bytes, other frames have a
# destination node ID which consumes the first byte of the message
if self.dest_node_id is None:
bytes_per_frame = 8
else:
bytes_per_frame = 7
out_frames = []
remaining_payload = self.payload
# Prepend the transfer CRC to the payload if the transfer requires
# multiple frames
if len(remaining_payload) > bytes_per_frame:
crc = common.crc16_from_bytes(self.payload, initial=datatype_crc)
remaining_payload = bytearray([crc & 0xFF, crc >> 8]) + \
remaining_payload
# Generate the frame sequence
while True:
frame = Frame(message_id=0)
frame.transfer_priority = self.transfer_priority
frame.transfer_id = self.transfer_id
frame.frame_index = len(out_frames)
frame.last_frame = len(remaining_payload) <= bytes_per_frame
frame.source_node_id = self.source_node_id
frame.data_type_id = self.data_type_id
frame.dest_node_id = self.dest_node_id
frame.payload = remaining_payload[0:bytes_per_frame]
frame.request_not_response = self.request_not_response
frame.broadcast_not_unicast = False if self.dest_node_id else True
out_frames.append(frame)
remaining_payload = remaining_payload[bytes_per_frame:]
if not remaining_payload:
break
return out_frames
def test_bytearray(self):
self.assertEqual(
common.crc16_from_bytes(bytearray('123456789', 'utf-8')),
0x29B1)
def test_bytes(self):
self.assertEqual(common.crc16_from_bytes(b'123456789'), 0x29B1)
def test_str(self):
self.assertEqual(common.crc16_from_bytes("123456789"), 0x29B1)
def test_bytearray(self):
self.assertEqual(common.crc16_from_bytes(bytearray("123456789", "utf-8")), 0x29B1)
