def serialize(self):
# serialize header
pkt = self._header()
# compute checksum over data
crc = checksum.crc8(0xFF)
crc.update(self.data)
crc.update(self.optData)
# append data and opt. data (if any)
if len(self.data) > 0:
pkt = pkt + self.data
if len(self.optData) > 0:
pkt = pkt + self.optData
# finaly add data checksum
pkt.append(crc.sum)
return pkt
def _header(self):
# Create header form data length and packet type
header = bytearray(struct.pack(">HBB", len(self.data), len(self.optData), self.pktType))
# compute checksum
crc = checksum.crc8(0xFF)
crc.update(header)
header.append(crc.sum)
# sync byte (not included in checksum)
header.insert(0, 0x55)
return header
def _header(self):
# Create header form data length and packet type
header = bytearray(
struct.pack('>HBB', len(self.data), len(self.optData),
self.pktType))
# compute checksum
crc = checksum.crc8(0xff)
crc.update(header)
header.append(crc.sum)
# sync byte (not included in checksum)
header.insert(0, 0x55)
return header
def serialize(self):
# serialize header
pkt = self._header()
# compute checksum over data
crc = checksum.crc8(0xff)
crc.update(self.data)
crc.update(self.optData)
# append data and opt. data (if any)
if len(self.data) > 0:
pkt = pkt + self.data
if len(self.optData) > 0:
pkt = pkt + self.optData
# finaly add data checksum
pkt.append(crc.sum)
return pkt
def read(self):
# initialize some local variables
pcktType = 0
PcktData = None
OptData = None
optLength = 0
# number of bytes to receive as next
n = 1
self._rxState = States.Idle
while not self._stop.isSet():
data = self._sp.read(n)
if len(data) == n:
# received enough bytes
data = bytearray(data)
if self._rxState == States.Idle:
if data[0] == 0x55:
self._rxState = States.Sync
# next we want to receive 4 header bytes + 1 crc
n = 5
elif self._rxState == States.Sync:
crc = checksum.crc8(0xFF)
crc.update(data)
if crc.valid():
# extract header
dataLength = (data[0] << 8) + data[1]
optLength = data[2]
pcktType = data[3]
# proceed to next rxState
self._rxState = States.Data
n = dataLength
else:
# Go back to idle (could be improved)
self._rxState = States.Idle
n = 1
elif self._rxState == States.Data:
PcktData = data
# proceed to next rxState
self._rxState = States.OptData
n = optLength
elif self._rxState == States.OptData:
OptData = data
# proceed to next rxState
self._rxState = States.Chk
n = 1
elif self._rxState == States.Chk:
# verify data
crc = checksum.crc8(0xFF)
crc.update(PcktData)
crc.update(OptData)
crc.update(data)
if crc.valid():
return ESP3BasePacket.factory(pcktType, PcktData, OptData)
# packet completed => back to idle
self._rxState = States.Idle
n = 1
else:
# timeout => back to idle
self._rxState = States.Idle
n = 1
def read(self):
# initialize some local variables
pcktType = 0
PcktData = None
OptData = None
optLength = 0
# number of bytes to receive as next
n = 1
self._rxState = States.Idle
while not self._stop.isSet():
data = self._sp.read(n)
if len(data) == n:
# received enough bytes
data = bytearray(data)
if self._rxState == States.Idle:
if data[0] == 0x55:
self._rxState = States.Sync
# next we want to receive 4 header bytes + 1 crc
n = 5
elif self._rxState == States.Sync:
crc = checksum.crc8(0xff)
crc.update(data)
if crc.valid():
# extract header
dataLength = (data[0] << 8) + data[1]
optLength = data[2]
pcktType = data[3]
# proceed to next rxState
self._rxState = States.Data
n = dataLength
else:
# Go back to idle (could be improved)
self._rxState = States.Idle
n = 1
elif self._rxState == States.Data:
PcktData = data
# proceed to next rxState
self._rxState = States.OptData
n = optLength
elif self._rxState == States.OptData:
OptData = data
# proceed to next rxState
self._rxState = States.Chk
n = 1
elif self._rxState == States.Chk:
# verify data
crc = checksum.crc8(0xff)
crc.update(PcktData)
crc.update(OptData)
crc.update(data)
if crc.valid():
return ESP3BasePacket.factory(pcktType, PcktData,
OptData)
# packet completed => back to idle
self._rxState = States.Idle
n = 1
else:
# timeout => back to idle
self._rxState = States.Idle
n = 1
