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CAN-FIX Protocol Implementation Library

Project Description

python-canfix is a Python package that abstracts the details of the CAN-FIX communication protocol.

CAN-FIX is the CAN bus implementation of a set of protocols and specifications known as FIX. FIX stands for Flight Information eXchange and is an attempt to standardize communication among aircraft systems in small aircraft.

The project is hosted on GitHub at…

https://github.com/birkelbach/python-canfix

Installation

Install can with pip:

$ pip install python-canfix

You can also install directly from the source directory by running:

$ python setup.py install

The only dependency is python-can, which should be automatically installed by the above commands.

API

You should be familiar with the CANFIX protocol specification before using this library. CANFIX has several different message types. Each of these types is representd by a class in this library.

NodeAlarm Class

The constructor can take one named parameter. msg can be assigned a python-can Message and the instantiated object will be initialized with the correct information.

Properties

NoneAlarm.node - Sets or returns the node address of the node that sent (or will send) the Alarm Message. Should be an integer between 1 and 254

NodeAlarm.alarm - Sets or returns the alarm type. The meaning of this data is dependent on the individual node type. Should be an integer between 0 and 65,535.

NodeAlarm.data - Sets or returns a list that represents the data for this alarm. What the data represents is dependent on the specific type of node and the alarm type. It should be a list of bytes of up to 6 bytes in length.

NodeAlarm.msg - Sets or returns a can.Message class that is suitable for use with a python-can bus. If this property is set with a message received from the can bus then the message will be parsed and the node, alarm and data properties will be set accordingly. If it is read then the message will be constructed with the node, alarm and data properties that should have been previously set.

Example Usage:

>>> na = canfix.NodeAlarm()
>>> na.node = 12
>>> na.alarm = 45321
>>> na.data = [4,5,6,7]
>>> na.msg
>>> na.msg
can.Message(timestamp=0.0, is_remote_frame=False, extended_id=False, is_error_frame=False, arbitration_id=0xc, dlc=0,
data=[0x9, 0xb1, 0x4, 0x5, 0x6, 0x7])

>>> msg = bus.recv() # Assume we read the same message that we created above
>>> na = canfix.NodeAlarm(msg)
>>> print(na)
[12] Node Alarm 45321 Data 04050607

Parameter Class

The constructor can take one named parameter. msg can be assigned a python-can Message and the instantiated object will be initialized with the correct information.

Properties

Parameter.node - Sets or returns the node address of the node that sent (or will send) the Parameter. Should be an integer between 1 and 254

Parameter.identifier - Sets or returns the CAN bus identifier for this parameter. If the identifier is out of of range for Parameter messages a ValueError exception will be raised. Setting this will also cause protocol specific information to be set in the object. This includes the data type, the engineering units, name etc.

Parameter.name - Sets or returns the name of the parameter. i.e. “Indicated Airspeed” If the name is not found in the protocol ValueError exception will be raised. Setting this will also cause protocol specific information to be set in the object. This includes the data type, the engineering units, identifier etc.

Parameter.index - Sets or returns the index of the parameter. Should be an integer between 0 and 255.

Parameter.failure - Sets or returns the flag that indicates data failure. Should be True or False

Parameter.quality - Sets or returns the flag that indicates data quality. Should be True or False

Parameter.annunciate - Sets or returns the flag that indicates the paramter should be annunciated. Should be True or False

Parameter.meta - Sets or returns the meta data index for the Parameter. Should be an integer between 0 and 15

Parameter.value - Sets or returns the value for the parameter. It can be a list of multiple values if the particular parameter is expecting multiple values. It can also be a string

Parameter.msg - Sets or returns a can.Message class that is suitable for use with a python-can bus. If this property is set with a message received from the can bus then the message will be parsed and the properties will be set accordingly. If it is read then the message will be constructed with properties that should have been previously set.

Parameter.fullName - Returns a string that represents the parameter that includes the index and the index name. This property is read only.

Parameter.units - Read only property that returns a string indicating the engineering units for this Parameter. This is a protocol specific piece of information and should not change.

Parameter.type - Read only property that returns a string indicating the datatype for the Parameter. This is a protocol specific piece of information and should not change.

Parameter.min - Read only property that returns a value that indicates the minimum value for the Parameter. This is a protocol specific piece of information and should not change.

Parameter.max - Read only property that returns a value that indicates the maximum value for the Parameter. This is a protocol specific piece of information and should not change.

Parameter.format - Read only property that returns the format of the data in the Parameter value. This is typically used to indicated what WORD and BYTE type data means. This is a protocol specific piece of information and should not change.

Parameter.remarks - Read only property that returns a list of remarks that are associated with this Parameter in the protocol specification. This is a protocol specific piece of information and should not change.

Parameter.indexName - Read only property that retuns he name of what the index represents. i.e. Cylinder This is a protocol specific piece of information and should not change.

Parameter.multiplier - Read only property that returns the multiplier for the Parameter. Some paramters use an integer with a multiplier as the value in the message. For example if we had a Parameter value of 123.4 and the multiplier is 0.1 then the data that would be communicated on the bus would be 1234. The receiver would then multiply by 0.1 to get the original value of 123.4. The python-canfix library handles these details for you so you don’t need to concern yourself with this detail. It is a part of the protocol and is included here for applications that want to display protocol specific information to the user. This is a protocol specific piece of information and should not change.

Example Usage:

>>> pa = canfix.Parameter()
>>> pa.node = 2
>>> pa.value = 123.4
>>> print(pa)
[2] Indicated Airspeed: 123.4 knots
>>> pa.msg
can.Message(timestamp=0.0, is_remote_frame=False, extended_id=False, is_error_frame=False, arbitration_id=0x183,
dlc=0, data=[0x2, 0x0, 0x0, 0xd2, 0x4])

TwoWayMsg Class

The constructor can take one named parameter. msg can be assigned a python-can Message and the instantiated object will be initialized with the correct information.

Properties

TwoWayMsg.channel - Sets the channel that this message will be sent on. There are 16 channels numbered 0-15

TwoWayMsg.type - Set to either ‘Request’ or ‘Response’ This determines which side of the channel to use.

TwoWayMsg.data - Up to eight bytes

NodeSpecific Class

The constructor can take one named parameter. msg can be assigned a python-can Message and the instantiated object will be initialized with the correct information.

Properties

NodeSpecific.destNode - Represents the node address of the node that this message is addressed to. Should be an integer between 1 and 254.

NodeSpecific.controlCode - The control code for the messge. Currently, valid values are 0-10. Future versions of the CAN-FIX specification may use 11-127 and values from 128 to 255 are reserved for user defined functions. The control code is basically the function of the message. See the CAN-FIX specification for details.

NodeSpecific.data - Up to 8 bytes of data that is dependent on which type of message that is being sent.

Functions

parseMessage(msg) - When passed a Message this function figures out what the message type is, instantiates the correct object type and returns that object. This function would be used for most all received messages.

Example Usage:

>>> msg = bus.recv()
>>> msg
can.Message(timestamp=0.0, is_remote_frame=False, extended_id=False,
is_error_frame=False, arbitration_id=0x183, dlc=5,
data=[0xc, 0x0, 0x0, 0xd2, 0x4])
>>> p = canfix.parseMessage(msg)
>>> p
<canfix.Parameter object at 0x7f6984fe9c10>
>>> print(p)
[12] Indicated Airspeed: 123.4 knots

Release history Release notifications

This version
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0.1.0

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