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Discussion Groups | LPC2000 | Can Bus termination on MCB2100
Discussion group dedicated to the Philips LPC2000 family of ARM MCUs
Can Bus termination on MCB2100 - David Jones - Feb 27 0:28:07 2008
WRT: Can Bus using MCB2100
In the notes under "Can Drivers" -Notes it says that you need to remove
the termination resistors 18 and 19 if using an external CAN Bus.
I propose to use the board in-vehicle so need to remove the termination.
It says that the termination resistors are R18 and R19
Looking at the circuit diagram, aren't R10, R16 , R17 and R18 the
termination resistors. Do all of these have to be removed?
Also R19 is on the 3.3V power LED ??
Thanks in advance
David Jones
[Non-text portions of this message have been removed]
(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )
In the notes under "Can Drivers" -Notes it says that you need to remove
the termination resistors 18 and 19 if using an external CAN Bus.
I propose to use the board in-vehicle so need to remove the termination.
It says that the termination resistors are R18 and R19
Looking at the circuit diagram, aren't R10, R16 , R17 and R18 the
termination resistors. Do all of these have to be removed?
Also R19 is on the 3.3V power LED ??
Thanks in advance
David Jones
[Non-text portions of this message have been removed]
(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )
Re: Can Bus termination on MCB2100 - mjames_doveridge - Feb 27 3:19:58 2008
--- In l...@yahoogroups.com, "David Jones" wrote:
>
> WRT: Can Bus using MCB2100
>
>
>
> In the notes under "Can Drivers" -Notes it says that you need to remove
> the termination resistors 18 and 19 if using an external CAN Bus.
> I propose to use the board in-vehicle so need to remove the termination.
The termination should be a at both ends of the network & so, ideally,
the need for termination on the board depends on where you intend to
connect the board to the vehicle wrt. the topology of the vehicle
network. If you tap in on the end, you should leave the termination
in on the board and remove it on the 'old' end-node in the vehicle.
I'm guessing that this is not practical
>
>
> It says that the termination resistors are R18 and R19
>
> Looking at the circuit diagram, aren't R10, R16 , R17 and R18 the
> termination resistors.
They are. The diagram, the silk-screen on the board and the physical
placement of the components all say 'R10-R16 for CAN1', 'R17-R18 for
CAN2'.
Do all of these have to be removed?
Well, this question only arises if you are connecting both CAN ports
to the vehicle.
As above, you should take into account the physical topology of the
vehcle network to decide whether your ports need the terminators or not.
The network may well work fine with incorrect terminators, (depending
on how bad the topology is made, bus speed and many other things),
but your testing may be be suspect.
I would probably take out the terminators, try to keep any 'stub'
short and see how many CAN errors I get.
At 50KHz, (the rate I use becasue of long networks in the field), it
does not seem to matter much where I put the terminators or how I wire
up the boards in the lab. Nevertheless, I have kept the network
terminated correctly for testing by leaving the MBC2100 terminators in
and making both CAN ports the physical ends of the network.
Rgds,
Martin
(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )
>
> WRT: Can Bus using MCB2100
>
>
>
> In the notes under "Can Drivers" -Notes it says that you need to remove
> the termination resistors 18 and 19 if using an external CAN Bus.
> I propose to use the board in-vehicle so need to remove the termination.
The termination should be a at both ends of the network & so, ideally,
the need for termination on the board depends on where you intend to
connect the board to the vehicle wrt. the topology of the vehicle
network. If you tap in on the end, you should leave the termination
in on the board and remove it on the 'old' end-node in the vehicle.
I'm guessing that this is not practical
>
>
> It says that the termination resistors are R18 and R19
>
> Looking at the circuit diagram, aren't R10, R16 , R17 and R18 the
> termination resistors.
They are. The diagram, the silk-screen on the board and the physical
placement of the components all say 'R10-R16 for CAN1', 'R17-R18 for
CAN2'.
Do all of these have to be removed?
Well, this question only arises if you are connecting both CAN ports
to the vehicle.
As above, you should take into account the physical topology of the
vehcle network to decide whether your ports need the terminators or not.
The network may well work fine with incorrect terminators, (depending
on how bad the topology is made, bus speed and many other things),
but your testing may be be suspect.
I would probably take out the terminators, try to keep any 'stub'
short and see how many CAN errors I get.
At 50KHz, (the rate I use becasue of long networks in the field), it
does not seem to matter much where I put the terminators or how I wire
up the boards in the lab. Nevertheless, I have kept the network
terminated correctly for testing by leaving the MBC2100 terminators in
and making both CAN ports the physical ends of the network.
Rgds,
Martin
(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )