RE: MCP2515 - Recovering from Error-Passive state

Chuck,
I think you are being overly conservative. 
Each Tx Error increments the error counter by 8.   That's a transmitted
message flagged as improperly formed by some _other_ node.  Each successful
transmission decrements the counter by 1.

Taking off the node with the high error count doesn't mean that node has the
problem.  It will likely be the node(s) that created error flag not
receiving the message correctly.
You haven't talked much about your protocol.  If you still have the
potential of two nodes sending the same ID with different data you are
hooped.  You will not solve the periodic bus disturbances.  And they will
happen often.  

It's been my experience that with larger networks the nodes tend to drift
together when sending messages so you end up with blocks of nodes
arbitrating.  If you aren't filtering properly then often nodes end up with
buffer overruns when you think you have a bus that is only loaded at 10%.
What you really have then is a bus that is 100% loaded for 10% of the time.


If you have some sort of heartbeat message sent by each node on a periodic
basis then have them include their TEC REC counters within the heartbeat.
Collect that information over a period of time and you might see a cluster
of nodes with problems.  Now you can look at either power supplies,
grounding or even bus reflections that tend to trash messages at certain
physical points.

I could tell you another story about that sort of thing for power line
networking using a CAN like protocol but I must run.

Cheers
John Dammeyer


> -----Original Message-----
> From: [email protected] [mailto:canlist-
> [email protected]] On Behalf Of Chuck Hackett
> Sent: September-10-14 11:31 AM
> To: [email protected]
> Subject: [CANLIST] MCP2515 - Recovering from Error-Passive state
> 
> I have done a lot of trial-and-error work on my MCP2515 driver and I think
I
> have most of the semantics of MCP2515 error recovery figured out.
> 
> Things seem to be in order except for recovery from Error-Passive state.
> 
> Currently I am canceling all xmit buffers and not attempting to send any
bus
> messages if the MCP2515 is not in Error-Active state (I realize this may
be
> overly conservative but it currently makes other things easier).  The
> firmware then monitors EFLG in background (I get no MCP2515 interrupts if
> no
> other nodes are sending) waiting for the MCP2515 to return to Error-Active
> state.
> 
> Apparently, to decrement the TEC counter the MCP2515 needs to actually
> attempt to send a message - or, is there some other way to get the MCP2515
> to exit Error-Passive?
> 
> I can periodically attempt to send a message when in Error-Passive state
but
> this doesn't feel quite right to me.
> 
> 
> 
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