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#
# Serial communication
#
# Copyright (c) 2013 Michael Buesch <m@bues.ch>
# Licensed under the terms of the GNU General Public License version 2.
#
import sys
import struct
import time
try:
import serial
except ImportError as e:
print("PLEASE INSTALL pyserial (https://pypi.python.org/pypi/pyserial)")
input("Press enter to exit.")
sys.exit(1)
class SerialError(Exception):
pass
class SerialMessage(object):
SER_HDR_LEN = 4
SER_FCS_LEN = 2
# Frame control
COMM_FC_RESET = 0x01
COMM_FC_REQ_ACK = 0x02
COMM_FC_ACK = 0x04
COMM_FC_ERRCODE = 0xC0
COMM_FC_ERRCODE_SHIFT = 6
# Frame error codes
COMM_ERR_OK = 0
COMM_ERR_FAIL = 1
COMM_ERR_FCS = 2
COMM_ERR_Q = 3
@classmethod
def crc16Update(cls, crc, data):
crc ^= data
for i in range(8):
if crc & 1:
crc = (crc >> 1) ^ 0xA001
else:
crc = crc >> 1
return crc
@classmethod
def crc16(cls, data):
crc = 0xFFFF
for d in data:
crc = cls.crc16Update(crc, d)
return crc ^ 0xFFFF
def __init__(self, fc=0, payload=b'', serialComm=None):
self.fc = fc
self.seq = 0
self.sa = 0
self.da = 0
self.payload = payload
self.fcs = 0
self.serialComm = serialComm
def copyHeaderFrom(self, fromMsg):
self.fc = fromMsg.fc
self.seq = fromMsg.seq
self.sa = fromMsg.sa
self.da = fromMsg.da
self.serialComm = fromMsg.serialComm
def calcFrameDuration(self):
"""Returns the duration of this frame, in seconds (float)."""
nrBytes = self.SER_HDR_LEN +\
self.serialComm.payloadLen +\
self.SER_FCS_LEN
symbolsPerByte = 1 + self.serialComm.serial.getByteSize() +\
(0 if (self.serialComm.serial.getParity() == serial.PARITY_NONE) else 1) +\
self.serialComm.serial.getStopbits()
return (nrBytes * symbolsPerByte) / self.serialComm.serial.getBaudrate()
def getErrorCode(self):
return (self.fc & self.COMM_FC_ERRCODE) >> self.COMM_FC_ERRCODE_SHIFT
def setSerialComm(self, serialComm):
self.serialComm = serialComm
def __calcFcs(self):
return self.crc16(self.__getBytes()[0 : -self.SER_FCS_LEN])
def getPayload(self):
return self.payload
def __getBytes(self):
payload = self.getPayload()
assert(len(payload) <= self.serialComm.payloadLen)
if len(payload) < self.serialComm.payloadLen:
payload += b'\x00' * (self.serialComm.payloadLen - len(payload))
fmtString = "%dB" % (self.SER_HDR_LEN +
self.serialComm.payloadLen +
self.SER_FCS_LEN)
arguments = [ self.fc & 0xFF,
self.seq & 0xFF,
(self.sa & 0xF) | ((self.da & 0xF) << 4),
0, ]
arguments.extend(list(payload))
arguments.extend([ self.fcs & 0xFF,
(self.fcs >> 8) & 0xFF, ])
return struct.pack(fmtString, *arguments)
def getBytes(self):
self.fcs = self.__calcFcs()
return self.__getBytes()
def __setBytes(self, data):
if len(data) != self.SER_HDR_LEN + self.serialComm.payloadLen + self.SER_FCS_LEN:
raise SerialError("Msg: Invalid number of bytes")
fmtString = "%dB" % (self.SER_HDR_LEN +
self.serialComm.payloadLen +
self.SER_FCS_LEN)
fields = struct.unpack(fmtString, data)
self.fc = fields[0]
self.seq = fields[1]
self.sa = fields[2] & 0xF
self.da = (fields[2] >> 4) & 0xF
self.payload = bytes(fields[self.SER_HDR_LEN :
self.SER_HDR_LEN + self.serialComm.payloadLen])
fcsLow = fields[self.SER_HDR_LEN +
self.serialComm.payloadLen]
fcsHigh = fields[self.SER_HDR_LEN +
self.serialComm.payloadLen + 1]
self.fcs = (fcsLow & 0xFF) | ((fcsHigh & 0xFF) << 8)
def setBytes(self, data):
self.__setBytes(data)
if self.__calcFcs() != self.fcs:
raise SerialError("Msg: FCS mismatch")
def __repr__(self):
ret = "SerialMessage: "
for b in self.getBytes():
ret += "%02X" % b
return ret
def send(self, destinationAddress=0, serialComm=None):
if not serialComm:
serialComm = self.serialComm
assert(serialComm)
serialComm.send(self, destinationAddress)
class SerialComm(object):
def __init__(self, device, baudrate=9600, nrbits=8,
parity=serial.PARITY_NONE, nrstop=1,
localAddress=1,
payloadLen=8,
debug=False):
try:
self.serial = serial.Serial(device, baudrate, nrbits,
parity, nrstop)
except (serial.SerialException, OSError) as e:
raise SerialError(str(e))
self.localAddress = localAddress
self.payloadLen = payloadLen
self.sendDelay = 0
self.seq = 0
self.debug = debug
def close(self):
try:
self.serial.close()
except (serial.SerialException, OSError) as e:
raise SerialError("Failed to close serial line: %s" % str(e))
def setSendDelay(self, seconds):
self.sendDelay = seconds
def poll(self):
try:
messageLength = SerialMessage.SER_HDR_LEN +\
self.payloadLen +\
SerialMessage.SER_FCS_LEN
if self.serial.inWaiting() < messageLength:
return None
while 1:
b = self.serial.read(messageLength)
msg = SerialMessage(serialComm = self)
msg.setBytes(b)
if msg.da == self.localAddress:
if self.debug:
print("Received raw message: %s" %\
str(msg))
return msg
if self.serial.inWaiting() < messageLength:
return None
except (serial.SerialException, OSError) as e:
raise SerialError("Serial receive failed: %s" % str(e))
def send(self, msg, destinationAddress=0):
try:
msg.sa = self.localAddress & 0xF
msg.da = destinationAddress & 0xF
msg.seq = self.seq
self.seq = (self.seq + 1) & 0xFF
msg.setSerialComm(self)
if self.debug:
print("Sending raw message: %s" % str(msg))
data = msg.getBytes()
if self.sendDelay:
for b in data:
self.serial.write(bytes((b,)))
self.serial.flush()
time.sleep(self.sendDelay)
else:
self.serial.write(data)
self.serial.flush()
except (serial.SerialException, OSError) as e:
raise SerialError("Serial send failed: %s" % str(e))
def sendSync(self, msg, destinationAddress=0, timeout=1.0):
self.send(msg, destinationAddress)
if msg.fc & msg.COMM_FC_REQ_ACK:
timeoutCount = timeout
while timeoutCount > 0.0:
res = self.poll()
if res is not None:
return res
time.sleep(0.01)
timeoutCount -= 0.01
raise SerialError("Serial send-sync failed: "
"Timeout of %.01f seconds exceed." %\
timeout)
return None
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