CAN-FD transport MAX_DLC_REQUIRED
danielhrisca opened this issue · 4 comments
I think that the way MAX_DLC_REQUIRED
is handled for CAN-FD should be revised.
In the current implementation this is automatically set to True for CAN-FD (see
Line 316 in 60a38cb
SRS_Can_01160
does not state that a maximum frame length must be used, it only talks about padding the frame up to the next CAN-FD DLC value, which is also correctly implemented in the pad_frame
function (
Line 78 in 60a38cb
SWS_Can_00502] ⌈ If PduInfo->SduLength does not match possible DLC values
CanDrv shall use the next higher valid DLC for transmission with initialization of
unused bytes to the value of the corresponding CanFdPaddingValue (see
ECUC_Can_00485).⌋ ( SRS_Can_01160)
On the other hand the XCP on CAN specification only talks about MAX_DLC_REQUIRED
which would then result in 8 or 64 bytes frames.
Yes, FD-frame padding is only required if SduLength does not exactly matches a discrete DLC value.
The fix will be included in the next big release.
And only for autosar
(disclaimer: I don't know XCP-over-CAN specification) The Autosar implementation from EB seem to require minimal DLC=8 on CANfd. It ignores shorter frames. C'est la vie...
The FD padding behavior is fixed in the (hopefully soon) coming release.