def encode_datagram(self, value):
protocol_version = value.get(
'protocol_version', PROTOCOL_MAJOR_VERSION)
timestamp = get_timestamp_or_now(value)
packet_seq = value.get('packet_seq', get_packet_sequence_number())
packet_type = value.get('packet_type', 0)
plugin_id = value.get('plugin_id', 0)
plugin_major_version = value.get('plugin_major_version', 0)
plugin_minor_version = value.get('plugin_minor_version', 0)
plugin_patch_version = value.get('plugin_patch_version', 0)
plugin_instance = value.get('plugin_instance', 0)
plugin_run_id = value.get('plugin_run_id', RUN_ID)
body = value['body']
body_length = len(body)
body_crc = crc8(body)
self.encode_uint(1, START_FLAG)
self.encode_uint(3, body_length)
self.encode_uint(1, protocol_version)
self.encode_uint(4, timestamp)
self.encode_uint(2, packet_seq)
self.encode_uint(1, packet_type)
self.encode_uint(2, plugin_id)
self.encode_uint(1, plugin_major_version)
self.encode_uint(1, plugin_minor_version)
self.encode_uint(1, plugin_patch_version)
self.encode_uint(1, plugin_instance)
self.encode_uint(2, plugin_run_id)
self.encode_bytes(body)
self.encode_uint(1, body_crc)
self.encode_uint(1, END_FLAG)
def request_data(self, sensors):
# Packaging
buffer = bytearray()
buffer.append(0xAA) # preamble
buffer.append(0x02) # data type (request) | protocol version (2)
buffer.append(len(buffer))
third_byte = 0x80 | self.SQN
if self.SQN < 0x7F:
self.SQN += 1
else:
self.SQN = 0
buffer.append(third_byte) # sequence ( 0 )
data = bytearray()
while (len(sensors) != 0):
if sensors[0] <= 0x06:
data.append(sensors[0]) # function type
data.append(0x01)
data.append(sensors[1]) # sensor id
sensors = sensors[2::]
elif sensors[0] >= 0x11 and sensors[0] <= 0x16:
data.append(sensors[0]) # function type
data.append(sensors[1]) # bus type
data.append(sensors[2]) # bus address
data.extend(sensors[3:sensors[1] + 2]) # parameters
sensors = sensors[sensors[1] + 2::]
buffer.extend(data)
buffer[2] = len(data) + 1
buffer.append(crc8(buffer[3:])) # crc
buffer.append(0x55) # postscript
self.serial.write(bytes(buffer))
return self.read_response()
def test_crc8(self):
test_cases = [
(bytes([]), 0),
(bytes([0x80]), 0x8c),
(bytes([1, 2, 3]), 216),
(bytes([0xff] * 1024), 201),
]
for data, crc in test_cases:
self.assertEqual(crc8(data), crc)
def read_response(self, timeout=180):
data = bytearray()
packets = bytearray()
# The response must be received within 3 minutes
for i in range(timeout * 2):
if self.serial.inWaiting() > 0 or len(data) > 0:
data.extend(self.serial.read(self.serial.inWaiting()))
while True:
try:
del data[:data.index(self.START_BYTE)]
except ValueError:
del data[:]
if len(data) >= self.HEADER_SIZE:
packet_length = data[2]
if len(
data
) >= self.HEADER_SIZE + packet_length + self.FOOTER_SIZE:
packet = data[:self.HEADER_SIZE + packet_length +
self.FOOTER_SIZE]
crc = packet[-2]
if crc != crc8(packet[self.HEADER_SIZE:-2]):
return None
sequence = data[3]
packets.extend(packet)
del data[:len(packet)]
if (sequence & 0x80) == 0x80:
return packets
else:
time.sleep(0.5)
break
else:
time.sleep(0.5)
break
else:
time.sleep(0.5)
# TIMEOUT: return packet that have been received
return packets
def decode_datagram(self):
start_flag = self.decode_uint(1)
if start_flag != START_FLAG:
raise ValueError('Invalid start flag.')
body_length = self.decode_uint(3)
protocol_version = self.decode_uint(1)
timestamp = self.decode_uint(4)
packet_seq = self.decode_uint(2)
packet_type = self.decode_uint(1)
plugin_id = self.decode_uint(2)
plugin_major_version = self.decode_uint(1)
plugin_minor_version = self.decode_uint(1)
plugin_patch_version = self.decode_uint(1)
plugin_instance = self.decode_uint(1)
plugin_run_id = self.decode_uint(2)
body = self.decode_bytes(body_length)
body_crc = self.decode_uint(1)
if crc8(body) != body_crc:
raise ValueError('Invalid body CRC.')
end_flag = self.decode_uint(1)
if end_flag != END_FLAG:
raise ValueError('Invalid end flag.')
return {
'timestamp': timestamp,
'packet_seq': packet_seq,
'packet_type': packet_type,
'plugin_id': plugin_id,
'plugin_major_version': plugin_major_version,
'plugin_minor_version': plugin_minor_version,
'plugin_patch_version': plugin_patch_version,
'plugin_instance': plugin_instance,
'plugin_run_id': plugin_run_id,
'body': body,
}