[CAN-FD] Vehicle Diagnostic Communication Part 93 [ISO-TP 1]

Click here for back issues.
https://www.simulationroom999.com/blog/diagnostic-communication-en-back-issue/

Introduction.
CAN-FD with can-isotp?
Simulation Configuration
Frame configuration for CAN-FD version
SingleFrame with 8 bytes or more
FirstFrame for multiframes of 4096 bytes or more
Conclusion

Introduction.

Explanation for the simulation of CAN-FD in CAN-ISOTP.
In this article, the simulation configuration and the changes in the frame configuration when it comes to CAN-FD will be explained.

CAN-FD with can-isotp?

Here is an explanation of CAN-FD as ISO 15765-2.
Probably, can-isotp can be used.

There is “can_fd” in the initialization parameter of the CanStack class.
If you enable it, you should be able to use can-isotp.
(I don’t know much about it)

Simulation Configuration

The simulation configuration is depicted as follows.
The configuration itself is the same as at CAN.

can-isotp experiment overall structure,diagnostic request,diagnostic response,python,iso-tp,can.logger,python-can,Virtual CAN Bus

It only changes the initialization parameters, so it does not affect the configuration.

Frame configuration for CAN-FD version

CAN-FD has a 64-byte DLC maximum, so the frame configuration changes in various ways.
Only SingleFrame and FirstFrame will be changed.

SingleFrame with 8 bytes or more

CAN-FD is the same as CAN if it is less than 7 bytes, but if it is more than 8 bytes, it is a little different.
It is as follows.

N_PCI of SingleFrame was 1 byte long, but it will be extended to 2 bytes.
If there is a 0 in the place where the original SingleFrame Length is inserted, the 1 byte after the 0 is considered to be the Length.

However, is it acceptable to send a message with a length of less than 8 bytes in this configuration?
The standard prohibits it.
Whenever this configuration of N_PCI is used, it is for cases that cannot be expressed by CAN.

FirstFrame for multiframes of 4096 bytes or more

Here is the explanation of FirstFrame as CAN-FD.
This is the case when the Length is 4096 bytes or more.
As in the case of SingleFrame, if the length is less than 4095 bytes, the configuration must not be used.

A 4-byte Length can be specified.
Thus, it is possible to set up to 4Gbyte-1byte!

However, it is unlikely that a buffer for communication can be prepared that much, so 8Kbyte or 16Kbyte would be realistic values, which are twice or four times as large as 4Kbyte.