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"""
Enable basic can over a serial device.
E.g. over bluetooth with "/dev/rfcomm0"
"""
import logging
logger = logging.getLogger('can.serial')
try:
import serial
except ImportError:
logger.error("You won't be able to use the serial can backend without the serial module installed!")
serial = None
from can.bus import BusABC
from can.message import Message
class SerialBus(BusABC):
def __init__(self, channel, *args, **kwargs):
"""A serial interface to CAN.
:param str channel:
The serial device to open.
"""
if channel == '':
raise TypeError("Must specify a serial port.")
else:
self.channel_info = "Serial interface: " + channel
# Note: Some serial port implementations don't care about the baud rate
self.ser = serial.Serial(channel, baudrate=115200, timeout=0.1)
super(SerialBus, self).__init__(*args, **kwargs)
def send(self, msg):
raise NotImplementedError("This serial interface doesn't support transmit.")
def recv(self, timeout=None):
try:
# ser.read can return an empty string ''
# or raise a SerialException
rx_byte = self.ser.read()
except serial.SerialException:
return None
if len(rx_byte) and ord(rx_byte) == 0xAA:
s = bytearray(self.ser.read(4))
timestamp = s[0] + (s[1] << 8) + (s[2] << 16) + (s[3] << 24)
dlc = ord(self.ser.read())
s = bytearray(self.ser.read(4))
arb_id = s[0] + (s[1] << 8) + (s[2] << 16) + (s[3] << 24)
data = self.ser.read(dlc)
rxd_byte = ord(self.ser.read())
if rxd_byte == 0xBB:
# received message data okay
return Message(timestamp=timestamp, arbitration_id=arb_id, dlc=dlc, data=data)
else:
return None
else:
return None
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