"""
NI-CAN interface module.
Implementation references:
* http://www.ni.com/pdf/manuals/370289c.pdf
* https://github.com/buendiya/NicanPython
TODO: We could implement this interface such that setting other filters
could work when the initial filters were set to zero using the
software fallback. Or could the software filters even be changed
after the connection was opened? We need to document that behaviour!
See also the IXXAT interface.
"""
import ctypes
import logging
import sys
from typing import Optional, Tuple, Type
import can.typechecking
from can import (
BusABC,
CanError,
CanInitializationError,
CanInterfaceNotImplementedError,
CanOperationError,
CanProtocol,
Message,
)
logger = logging.getLogger(__name__)
NC_SUCCESS = 0
NC_ERR_TIMEOUT = 1
TIMEOUT_ERROR_CODE = -1074388991
NC_DURATION_INFINITE = 0xFFFFFFFF
NC_OP_START = 0x80000001
NC_OP_STOP = 0x80000002
NC_OP_RESET = 0x80000003
NC_FRMTYPE_REMOTE = 1
NC_FRMTYPE_COMM_ERR = 2
NC_ST_READ_AVAIL = 0x00000001
NC_ST_WRITE_SUCCESS = 0x00000002
NC_ST_ERROR = 0x00000010
NC_ST_WARNING = 0x00000020
NC_ATTR_BAUD_RATE = 0x80000007
NC_ATTR_START_ON_OPEN = 0x80000006
NC_ATTR_READ_Q_LEN = 0x80000013
NC_ATTR_WRITE_Q_LEN = 0x80000014
NC_ATTR_CAN_COMP_STD = 0x80010001
NC_ATTR_CAN_MASK_STD = 0x80010002
NC_ATTR_CAN_COMP_XTD = 0x80010003
NC_ATTR_CAN_MASK_XTD = 0x80010004
NC_ATTR_LOG_COMM_ERRS = 0x8001000A
NC_FL_CAN_ARBID_XTD = 0x20000000
CanData = ctypes.c_ubyte * 8
class RxMessageStruct(ctypes.Structure):
_pack_ = 1
_fields_ = [
("timestamp", ctypes.c_ulonglong),
("arb_id", ctypes.c_ulong),
("frame_type", ctypes.c_ubyte),
("dlc", ctypes.c_ubyte),
("data", CanData),
]
class TxMessageStruct(ctypes.Structure):
_fields_ = [
("arb_id", ctypes.c_ulong),
("is_remote", ctypes.c_ubyte),
("dlc", ctypes.c_ubyte),
("data", CanData),
]
[docs]
class NicanError(CanError):
"""Error from NI-CAN driver."""
def __init__(self, function, error_code: int, arguments) -> None:
super().__init__(
message=f"{function} failed: {get_error_message(self.error_code)}",
error_code=error_code,
)
#: Function that failed
self.function = function
#: Arguments passed to function
self.arguments = arguments
[docs]
class NicanInitializationError(NicanError, CanInitializationError):
pass
class NicanOperationError(NicanError, CanOperationError):
pass
def check_status(
result: int,
function,
arguments,
error_class: Type[NicanError] = NicanOperationError,
) -> int:
if result > 0:
logger.warning(get_error_message(result))
elif result < 0:
raise error_class(function, result, arguments)
return result
def check_status_init(*args, **kwargs) -> int:
return check_status(*args, **kwargs, error_class=NicanInitializationError)
def get_error_message(status_code: int) -> str:
"""Convert status code to descriptive string."""
errmsg = ctypes.create_string_buffer(1024)
nican.ncStatusToString(status_code, len(errmsg), errmsg)
return errmsg.value.decode("ascii")
if sys.platform == "win32":
try:
nican = ctypes.windll.LoadLibrary("nican")
except Exception as e:
nican = None
logger.error("Failed to load NI-CAN driver: %s", e)
else:
nican.ncConfig.argtypes = [
ctypes.c_char_p,
ctypes.c_ulong,
ctypes.c_void_p,
ctypes.c_void_p,
]
nican.ncConfig.errcheck = check_status_init
nican.ncOpenObject.argtypes = [ctypes.c_char_p, ctypes.c_void_p]
nican.ncOpenObject.errcheck = check_status_init
nican.ncCloseObject.errcheck = check_status
nican.ncAction.argtypes = [ctypes.c_ulong, ctypes.c_ulong, ctypes.c_ulong]
nican.ncAction.errcheck = check_status
nican.ncRead.errcheck = check_status
nican.ncWrite.errcheck = check_status
nican.ncWaitForState.argtypes = [
ctypes.c_ulong,
ctypes.c_ulong,
ctypes.c_ulong,
ctypes.c_void_p,
]
nican.ncWaitForState.errcheck = check_status
nican.ncStatusToString.argtypes = [ctypes.c_int, ctypes.c_uint, ctypes.c_char_p]
else:
nican = None
logger.warning("NI-CAN interface is only available on Windows systems")
[docs]
class NicanBus(BusABC):
"""
The CAN Bus implemented for the NI-CAN interface.
.. warning::
This interface does implement efficient filtering of messages, but
the filters have to be set in ``__init__`` using the ``can_filters`` parameter.
Using :meth:`~can.BusABC.set_filters` does not work.
"""
def __init__(
self,
channel: str,
can_filters: Optional[can.typechecking.CanFilters] = None,
bitrate: Optional[int] = None,
log_errors: bool = True,
**kwargs,
) -> None:
"""
:param channel:
Name of the object to open (e.g. `"CAN0"`)
:param bitrate:
Bitrate in bit/s
:param can_filters:
See :meth:`can.BusABC.set_filters`.
:param log_errors:
If True, communication errors will appear as CAN messages with
``is_error_frame`` set to True and ``arbitration_id`` will identify
the error (default True)
:raise ~can.exceptions.CanInterfaceNotImplementedError:
If the current operating system is not supported or the driver could not be loaded.
:raise ~can.interfaces.nican.NicanInitializationError:
If the bus could not be set up.
"""
if nican is None:
raise CanInterfaceNotImplementedError(
"The NI-CAN driver could not be loaded. "
"Check that you are using 32-bit Python on Windows."
)
self.channel = channel
self.channel_info = f"NI-CAN: {channel}"
self._can_protocol = CanProtocol.CAN_20
channel_bytes = channel.encode("ascii")
config = [(NC_ATTR_START_ON_OPEN, True), (NC_ATTR_LOG_COMM_ERRS, log_errors)]
if not can_filters:
logger.info("Filtering has been disabled")
config.extend(
[
(NC_ATTR_CAN_COMP_STD, 0),
(NC_ATTR_CAN_MASK_STD, 0),
(NC_ATTR_CAN_COMP_XTD, 0),
(NC_ATTR_CAN_MASK_XTD, 0),
]
)
else:
for can_filter in can_filters:
can_id = can_filter["can_id"]
can_mask = can_filter["can_mask"]
logger.info("Filtering on ID 0x%X, mask 0x%X", can_id, can_mask)
if can_filter.get("extended"):
config.extend(
[
(NC_ATTR_CAN_COMP_XTD, can_id | NC_FL_CAN_ARBID_XTD),
(NC_ATTR_CAN_MASK_XTD, can_mask),
]
)
else:
config.extend(
[
(NC_ATTR_CAN_COMP_STD, can_id),
(NC_ATTR_CAN_MASK_STD, can_mask),
]
)
if bitrate:
config.append((NC_ATTR_BAUD_RATE, bitrate))
AttrList = ctypes.c_ulong * len(config)
attr_id_list = AttrList(*(row[0] for row in config))
attr_value_list = AttrList(*(row[1] for row in config))
nican.ncConfig(
channel_bytes,
len(config),
ctypes.byref(attr_id_list),
ctypes.byref(attr_value_list),
)
self.handle = ctypes.c_ulong()
nican.ncOpenObject(channel_bytes, ctypes.byref(self.handle))
super().__init__(
channel=channel,
can_filters=can_filters,
bitrate=bitrate,
log_errors=log_errors,
**kwargs,
)
def _recv_internal(
self, timeout: Optional[float]
) -> Tuple[Optional[Message], bool]:
"""
Read a message from a NI-CAN bus.
:param timeout:
Max time to wait in seconds or ``None`` if infinite
:raises can.interfaces.nican.NicanOperationError:
If reception fails
"""
if timeout is None:
timeout = NC_DURATION_INFINITE
else:
timeout = int(timeout * 1000)
state = ctypes.c_ulong()
try:
nican.ncWaitForState(
self.handle, NC_ST_READ_AVAIL, timeout, ctypes.byref(state)
)
except NicanError as e:
if e.error_code == TIMEOUT_ERROR_CODE:
return None, True
else:
raise
raw_msg = RxMessageStruct()
nican.ncRead(self.handle, ctypes.sizeof(raw_msg), ctypes.byref(raw_msg))
# http://stackoverflow.com/questions/6161776/convert-windows-filetime-to-second-in-unix-linux
timestamp = raw_msg.timestamp / 10000000.0 - 11644473600
is_remote_frame = raw_msg.frame_type == NC_FRMTYPE_REMOTE
is_error_frame = raw_msg.frame_type == NC_FRMTYPE_COMM_ERR
is_extended = bool(raw_msg.arb_id & NC_FL_CAN_ARBID_XTD)
arb_id = raw_msg.arb_id
if not is_error_frame:
arb_id &= 0x1FFFFFFF
dlc = raw_msg.dlc
msg = Message(
timestamp=timestamp,
channel=self.channel,
is_remote_frame=is_remote_frame,
is_error_frame=is_error_frame,
is_extended_id=is_extended,
arbitration_id=arb_id,
dlc=dlc,
data=raw_msg.data[:dlc],
)
return msg, True
def send(self, msg: Message, timeout: Optional[float] = None) -> None:
"""
Send a message to NI-CAN.
:param msg:
Message to send
:param timeout:
The timeout
.. warning:: This gets ignored.
:raises can.interfaces.nican.NicanOperationError:
If writing to transmit buffer fails.
It does not wait for message to be ACKed currently.
"""
arb_id = msg.arbitration_id
if msg.is_extended_id:
arb_id |= NC_FL_CAN_ARBID_XTD
raw_msg = TxMessageStruct(
arb_id, bool(msg.is_remote_frame), msg.dlc, CanData(*msg.data)
)
nican.ncWrite(self.handle, ctypes.sizeof(raw_msg), ctypes.byref(raw_msg))
# TODO:
# ncWaitForState can not be called here if the recv() method is called
# from a different thread, which is a very common use case.
# Maybe it is possible to use ncCreateNotification instead but seems a
# bit overkill at the moment.
# state = ctypes.c_ulong()
# nican.ncWaitForState(self.handle, NC_ST_WRITE_SUCCESS, int(timeout * 1000), ctypes.byref(state))
def reset(self) -> None:
"""
Resets network interface. Stops network interface, then resets the CAN
chip to clear the CAN error counters (clear error passive state).
Resetting includes clearing all entries from read and write queues.
:raises can.interfaces.nican.NicanOperationError:
If resetting fails.
"""
nican.ncAction(self.handle, NC_OP_RESET, 0)
def shutdown(self) -> None:
"""Close object."""
super().shutdown()
nican.ncCloseObject(self.handle)