def _port_pollin(self):
chars = self._port.drain()
if self._buffer is None:
self._buffer = array.array('c')
self._packet_length = 4 #shortest legit packet
self._buffer.extend(chars)
if len(
self._buffer
) >= self._packet_length: #might be a good packet, otherwise wait for more
packet_type = ord(self._buffer[1])
if not packet_type_vs_length.has_key(
packet_type): #don't crock this one
self._buffer = None #reset the packet processing
return
packet_length = packet_type_vs_length[packet_type]
if packet_length < 0: #must be variable length packet
packet_length = abs(packet_length)
if len(self._buffer
) < packet_length: #not enough of the packet in yet
return #try again when more comes in
packet_length = packet_length + ord(
self._buffer[packet_length -
3]) #calc variable length packet size
if len(self._buffer) >= packet_length: #enought to test the crc
chars = self._buffer
self._buffer = None #reset packet parsing regardless of what happens below
bbuffer = array.array('B', chars[:packet_length].tostring())
#is checksum good?
if crc(bbuffer) == 0: #things is gud
if debug:
print 'command'
dump(chars)
response = self.owner.command(chars)
if response is None: # message sent to a Modbus that does not exist
return
response.append_crc()
if debug:
print 'response:', response
dump(response.buffer)
self._port.write(response.buffer)
# If this is a Megatron RS485 port then consume echoed transmit characters
# Wait for up to 2 seconds to see our echoed transmit data.
if self.megatron_485:
try:
self.port.read(array.array('c'),
len(response.buffer), 2.0)
except:
msglog.exception()
else:
if debug:
print 'crc failed - might be response'
return
def _port_pollin(self):
chars = self._port.drain()
if self._buffer is None:
self._buffer = array.array("c")
self._packet_length = 4 # shortest legit packet
self._buffer.extend(chars)
if len(self._buffer) >= self._packet_length: # might be a good packet, otherwise wait for more
packet_type = ord(self._buffer[1])
if not packet_type_vs_length.has_key(packet_type): # don't crock this one
self._buffer = None # reset the packet processing
return
packet_length = packet_type_vs_length[packet_type]
if packet_length < 0: # must be variable length packet
packet_length = abs(packet_length)
if len(self._buffer) < packet_length: # not enough of the packet in yet
return # try again when more comes in
packet_length = packet_length + ord(self._buffer[packet_length - 3]) # calc variable length packet size
if len(self._buffer) >= packet_length: # enought to test the crc
chars = self._buffer
self._buffer = None # reset packet parsing regardless of what happens below
bbuffer = array.array("B", chars[:packet_length].tostring())
# is checksum good?
if crc(bbuffer) == 0: # things is gud
if debug:
print "command"
dump(chars)
response = self.owner.command(chars)
if response is None: # message sent to a Modbus that does not exist
return
response.append_crc()
if debug:
print "response:", response
dump(response.buffer)
self._port.write(response.buffer)
# If this is a Megatron RS485 port then consume echoed transmit characters
# Wait for up to 2 seconds to see our echoed transmit data.
if self.megatron_485:
try:
self.port.read(array.array("c"), len(response.buffer), 2.0)
except:
msglog.exception()
else:
if debug:
print "crc failed - might be response"
return
def crc(self, byte_array):
return base.crc(byte_array)
def crc(self, byte_array):
return base.crc(byte_array)