RE: CANOpen illegal messages

Hi Uwe,
Thanks for the feedback.  The problem showed up when a client's product
appeared to be either producing a 0 length NMT or responding to a 0 length
NMT by entering STOP.
Turns out it was my code that was generating the 0 length NMT and their
product handling it badly.  
On my end it turns out the PIC30 C compiler wasn't catching an array that
was improperly subscripted.  So the data passed to the CAN Send routine had
garbage in it.  Only happened when my software had a heartbeat at exactly
the same time as an SDO and the message was placed into the transmit Q
rather than directly to the CAN hardware.
The up side is we've found an issue in our client's product and they will
fix that on their next revision.  And I've learned to not trust the PIC30 C
compiler.  It was probably doing what I told it but not what I was thinking
I told it.
John
 
 
 
From: [email protected]
[mailto:[email protected]] On Behalf Of Uwe Koppe
Sent: May-03-15 10:56 PM
To: [email protected]
Subject: Re: [CANLIST] CANOpen illegal messages
 
Hi John,

the official CANopen position is that only NMT messages with the correct
DLC value (i.e. 2) are processed, other DLC values are ignored.There
is no service (EMCY) defined to report an incorrect NMT message.

BTW: in our CANopen stack we have a hook function for those "malformed"
NMT messages, because several CAN bootloaders (e.g. ATMEL) use the ID 0
for their own protocol.

Best regards,
Uwe
 
Thanks.  Specifically I'm wondering what the official CANOpen position is on
this.  I believe a node should ignore incorrectly formed messages.  Just
wondering if it's a rule for CANOpen.
 
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