Seeing CAN I/O Type

[robv1234]

I was just wondering if there was a way to see if a CAN signal is readable or writable before you actually deploy it in a session? Whether that's through property nodes or other means. 

[GerdW]

Hi rob,

how do you differ between "read" and "write"?

You know you can send the message containing your signal even though there might be a different device sending the same message on your CAN bus?

[robv1234]

Thanks for the reply, that makes sense from a CAN perspective but to clarify... Is there a way (before I actually deploy a session) to tell which signals in a DBC are intended to be transmitted by my node versus signals that are only ever received from other ECUs?

[Minions]

rob,

It would need to be defined as either a CHARACTERISITC or MEASUREMENT within the DBC file.  As to IF it is writeable, that may be another story.  Some segments are locked and require running a separate flash kernel in order to gain access to some locations.  This all depends on who owns the firmware and how it was designed with respect to expectations of the user/environment.

[GerdW]

Hi rob,

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@robv1234 wrote:

Is there a way (before I actually deploy a session) to tell which signals in a DBC are intended to be transmitted by my node versus signals that are only ever received from other ECUs?

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The DBC files I worked with usually defined the "owner" of the messages defined in the DBC. (My background is "listening to automobile ECU CAN bus" while "commanding devices on a different CAN bus".)

Usually there is a section in the DBC file defining all participants on the CAN bus and (usually) messages are assigned to those devices!

[ZYOng]

DBC file contains ECU information, which store the transmitting and receiving frames.

You could parse this information to see which the direction of the frames from a certain node point of view, but XNET won't stop you from writing/sending a "receiving frames".

[robv1234]

A follow up question I had is can you also parse the information to see which signals are digital and which are analog?

[GerdW]

Hi rob,

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@robv1234 wrote:

A follow up question I had is can you also parse the information to see which signals are digital and which are analog?

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All CAN signals are digital, they consist of one or more bits…

I guess you want to know how many bits are used by the signal?

Yes, this information is in the DBC! Each signal is defined by its bit position inside the message and the number of bits used for the signal…

[Minions]

Also, arrays of values are noted as a MATRIX within a CHARACTERISTIC.  There are several types of arrays.