Ao.Can

The Ao.Can namespace contains some useful stuff for dealing with CAN messages.

I have been using this code in conjunction with a self-made CAN sniffer, in order to log all messages being sent on a particular CAN bus, such as a vehicle’s powertrain bus.

CAN Message

The CAN struct carries all properties that a CAN message can possibly have. Note that depending on the message format (standard or extended) and message type (data or remote), some properties are irrelevant and need to be ignored.

Property
`Data`	Each data message carries up to 8 bytes of data or payload. Single bytes or bits can be gotten or set using the extension methods defined in the Ao.Bits namespace. The property is irrelevant for remote messages, since these do not carry data.
`DLC`	The data length code indicates the number of data bytes in data messages. It is irrelevant in remote messages.
`EID`	The extension identifier specifies the 18 least significant bits of the identifier of an extended message. It is irrelevant for standard messages.
`IDE`	The identifier extension specifies whether the message is a standard message (`false`) or an extended messages (`true`).
`RTR`	The remote transmission request specifies whether the message is a data message (`false`) or a remote messages (`true`).
`SID`	The standard identifier is the identifier of a standard message. In case of an extended message, this property specifies the 11 most significant bits of its identifier.
`XID`	This property gets or sets the entire 29-bit identifier and is thus relevant only for extended messages.

CAN Message Statistics

When logging traffic on a CAN bus in order to track down software bugs or general misbehavior of embedded controllers in a vehicle, it is quite useful to have an outline of all types of messages being sent, as well as their frequencies.

The CANStat class generates such an outline.

var Stat = new CANStat();

Whenever a new message arrives, simply hand it over, together with a time stamp.

void OnCAN(Time T, CAN C)
{
    Stat.Add(T, C);
}

Afterwards, the outline can be accessed via the object’s properties.

Property	Outline for all recorded …
`Extended.Data`	… extended data messages.
`Extended.Remote`	… extended remote messages.
`Standard.Data`	… standard data messages.
`Standard.Remote`	… standard remote messages.

Example 1

Print a list of all 29-bit identifiers of extended data messages.

foreach (var i in Stat.Extended.Data.XID)
{
    Console.WriteLine("{0:X8}", i);
}

...
18FDC40B
18FE4AEF
18FE592F
18FEAD0B
18FEBF0B
18FEC1EE
18FECAEF
18FEDFEF
18FEE617
18FEE6EE
18FEEA2F
18FEEEEF
18FEF111
18FEF1EF
...

Example 2

Print a list of all periods of extended data messages.

var T = Stat.Extended.Data.Time;

foreach (var i in T.Keys)
{
    var t1 = T[i].TimespanAverage.Milliseconds;

    var t2 = Round.HalfUp(t1);

    Console.WriteLine("{0:X8} : {1} ms", i, t2);
}

...
18FDC40B : 101 ms
18FE4AEF : 116 ms
18FE592F : 100 ms
18FEAD0B : 101 ms
18FEBF0B : 51 ms
18FEC1EE : 1008 ms
18FECAEF : 5906 ms
18FEDFEF : 288 ms
18FEE617 : 9998 ms
18FEE6EE : 1000 ms
18FEEA2F : 1009 ms
18FEEEEF : 443 ms
18FEF111 : 100 ms
18FEF1EF : 116 ms
...

Example 3

For the extended data message, whose 29-bit identifier is 18FEAD0B, print a list of all distinct data values.

var E1 = Stat.Extended.Data.Data[0x18FEAD0B].Entries;

var E2 = from x in E1 select x.Data;

var E3 = E2.Distinct();

var E4 = from x in E3 orderby x select x;

foreach (var x in E4)
{
    Console.WriteLine("{0:X16}", x);
}

...
FFFFFFFF211F2020
FFFFFFFF21211111
FFFFFFFF23231515
FFFFFFFF322F1D1D
FFFFFFFF33321E1E
FFFFFFFF35322323
FFFFFFFF37372121
FFFFFFFF3D3D2525
FFFFFFFF3E3B2525
FFFFFFFF3E3C2525
FFFFFFFF3E3F2626
FFFFFFFF40422727
FFFFFFFF40442A2A
FFFFFFFF41432929
...