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|
"""
To Support the Seeed USB-Can analyzer interface. The device will appear
as a serial port, for example "/dev/ttyUSB0" on Linux machines
or "COM1" on Windows.
https://www.seeedstudio.com/USB-CAN-Analyzer-p-2888.html
SKU 114991193
"""
import io
import logging
import struct
from time import time
import can
from can import BusABC, CanProtocol, Message
logger = logging.getLogger("seeedbus")
try:
import serial
except ImportError:
logger.warning(
"You won't be able to use the serial can backend without "
"the serial module installed!"
)
serial = None
class SeeedBus(BusABC):
"""
Enable basic can communication over a USB-CAN-Analyzer device.
"""
BITRATE = {
1000000: 0x01,
800000: 0x02,
500000: 0x03,
400000: 0x04,
250000: 0x05,
200000: 0x06,
125000: 0x07,
100000: 0x08,
50000: 0x09,
20000: 0x0A,
10000: 0x0B,
5000: 0x0C,
}
FRAMETYPE = {"STD": 0x01, "EXT": 0x02}
OPERATIONMODE = {
"normal": 0x00,
"loopback": 0x01,
"silent": 0x02,
"loopback_and_silent": 0x03,
}
def __init__(
self,
channel,
baudrate=2000000,
timeout=0.1,
frame_type="STD",
operation_mode="normal",
bitrate=500000,
**kwargs,
):
"""
:param str channel:
The serial device to open. For example "/dev/ttyS1" or
"/dev/ttyUSB0" on Linux or "COM1" on Windows systems.
:param baudrate:
The default matches required baudrate
:param float timeout:
Timeout for the serial device in seconds (default 0.1).
:param str frame_type:
STD or EXT, to select standard or extended messages
:param operation_mode
normal, loopback, silent or loopback_and_silent.
:param bitrate
CAN bus bit rate, selected from available list.
:raises can.CanInitializationError: If the given parameters are invalid.
:raises can.CanInterfaceNotImplementedError: If the serial module is not installed.
"""
if serial is None:
raise can.CanInterfaceNotImplementedError(
"the serial module is not installed"
)
self.bit_rate = bitrate
self.frame_type = frame_type
self.op_mode = operation_mode
self.filter_id = bytearray([0x00, 0x00, 0x00, 0x00])
self.mask_id = bytearray([0x00, 0x00, 0x00, 0x00])
self._can_protocol = CanProtocol.CAN_20
if not channel:
raise can.CanInitializationError("Must specify a serial port.")
self.channel_info = "Serial interface: " + channel
try:
self.ser = serial.Serial(
channel, baudrate=baudrate, timeout=timeout, rtscts=False
)
except ValueError as error:
raise can.CanInitializationError(
"could not create the serial device"
) from error
super().__init__(channel=channel, **kwargs)
self.init_frame()
def shutdown(self):
"""
Close the serial interface.
"""
super().shutdown()
self.ser.close()
def init_frame(self, timeout=None):
"""
Send init message to setup the device for comms. this is called during
interface creation.
:param timeout:
This parameter will be ignored. The timeout value of the channel is
used instead.
"""
byte_msg = bytearray()
byte_msg.append(0xAA) # Frame Start Byte 1
byte_msg.append(0x55) # Frame Start Byte 2
byte_msg.append(0x12) # Initialization Message ID
byte_msg.append(SeeedBus.BITRATE[self.bit_rate]) # CAN Baud Rate
byte_msg.append(SeeedBus.FRAMETYPE[self.frame_type])
byte_msg.extend(self.filter_id)
byte_msg.extend(self.mask_id)
byte_msg.append(SeeedBus.OPERATIONMODE[self.op_mode])
byte_msg.append(0x01) # Follows 'Send once' in windows app.
byte_msg.extend([0x00] * 4) # Manual bitrate config, details unknown.
crc = sum(byte_msg[2:]) & 0xFF
byte_msg.append(crc)
logger.debug("init_frm:\t%s", byte_msg.hex())
try:
self.ser.write(byte_msg)
except Exception as error:
raise can.CanInitializationError("could send init frame") from error
def flush_buffer(self):
self.ser.flushInput()
def status_frame(self, timeout=None):
"""
Send status request message over the serial device. The device will
respond but details of error codes are unknown but are logged - DEBUG.
:param timeout:
This parameter will be ignored. The timeout value of the channel is
used instead.
"""
byte_msg = bytearray()
byte_msg.append(0xAA) # Frame Start Byte 1
byte_msg.append(0x55) # Frame Start Byte 2
byte_msg.append(0x04) # Status Message ID
byte_msg.append(0x00) # In response packet - Rx error count
byte_msg.append(0x00) # In response packet - Tx error count
byte_msg.extend([0x00] * 14)
crc = sum(byte_msg[2:]) & 0xFF
byte_msg.append(crc)
logger.debug("status_frm:\t%s", byte_msg.hex())
self._write(byte_msg)
def send(self, msg, timeout=None):
"""
Send a message over the serial device.
:param can.Message msg:
Message to send.
:param timeout:
This parameter will be ignored. The timeout value of the channel is
used instead.
"""
byte_msg = bytearray()
byte_msg.append(0xAA)
m_type = 0xC0
if msg.is_extended_id:
m_type += 1 << 5
if msg.is_remote_frame:
m_type += 1 << 4
m_type += msg.dlc
byte_msg.append(m_type)
if msg.is_extended_id:
a_id = struct.pack("<I", msg.arbitration_id)
else:
a_id = struct.pack("<H", msg.arbitration_id)
byte_msg.extend(a_id)
byte_msg.extend(msg.data)
byte_msg.append(0x55)
logger.debug("sending:\t%s", byte_msg.hex())
self._write(byte_msg)
def _write(self, byte_msg: bytearray) -> None:
try:
self.ser.write(byte_msg)
except serial.PortNotOpenError as error:
raise can.CanOperationError("writing to closed port") from error
except serial.SerialTimeoutException as error:
raise can.CanTimeoutError() from error
def _recv_internal(self, timeout):
"""
Read a message from the serial device.
:param timeout:
.. warning::
This parameter will be ignored. The timeout value of the
channel is used.
:returns:
Received message and False (because not filtering as taken place).
:rtype:
can.Message, bool
"""
try:
# ser.read can return an empty string
# or raise a SerialException
rx_byte_1 = self.ser.read()
except serial.PortNotOpenError as error:
raise can.CanOperationError("reading from closed port") from error
except serial.SerialException:
return None, False
if rx_byte_1 and ord(rx_byte_1) == 0xAA:
try:
rx_byte_2 = ord(self.ser.read())
time_stamp = time()
if rx_byte_2 == 0x55:
status = bytearray([0xAA, 0x55])
status += bytearray(self.ser.read(18))
logger.debug("status resp:\t%s", status.hex())
else:
length = int(rx_byte_2 & 0x0F)
is_extended = bool(rx_byte_2 & 0x20)
is_remote = bool(rx_byte_2 & 0x10)
if is_extended:
s_3_4_5_6 = bytearray(self.ser.read(4))
arb_id = (struct.unpack("<I", s_3_4_5_6))[0]
else:
s_3_4 = bytearray(self.ser.read(2))
arb_id = (struct.unpack("<H", s_3_4))[0]
data = bytearray(self.ser.read(length))
end_packet = ord(self.ser.read())
if end_packet == 0x55:
msg = Message(
timestamp=time_stamp,
arbitration_id=arb_id,
is_extended_id=is_extended,
is_remote_frame=is_remote,
dlc=length,
data=data,
)
logger.debug("recv message: %s", str(msg))
return msg, False
else:
return None, False
except serial.PortNotOpenError as error:
raise can.CanOperationError("reading from closed port") from error
except serial.SerialException as error:
raise can.CanOperationError(
"failed to read message information"
) from error
return None, None
def fileno(self):
try:
return self.ser.fileno()
except io.UnsupportedOperation as excption:
logger.warning(
"fileno is not implemented using current CAN bus: %s", str(excption)
)
return -1
|
