Hi All
Can the CAN ports on the LPC2200 be configured to be used as RS485
ports?
If so has anyone done or knows how to do it.
I am using an LPC2294 demo board with CAN drivers.
Regards
Jean-Jacques
Can the CAN Ports on the LPC2200 be used as RS485
Started by ●November 23, 2007
Reply by ●November 23, 20072007-11-23
jdauchot schrieb:
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
I am not sure, but isn´t CAN packet based ? The UARTS might be
the right peripheral for this.
--
42Bastian
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
I am not sure, but isn´t CAN packet based ? The UARTS might be
the right peripheral for this.
--
42Bastian
Reply by ●November 23, 20072007-11-23
--- In l..., "jdauchot" wrote:
>
> Hi All
>
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
>
> If so has anyone done or knows how to do it.
>
> I am using an LPC2294 demo board with CAN drivers.
>
RS485 is an physical spec, CAN has a different physical spec and
specifies a packet protocol as well, complete with addressing and
arbitration mechanisms.
What you seem to be asking for would be 'very, very difficult',
(trying not to use the 'i' word).
Rgds,
Martin
>
> Hi All
>
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
>
> If so has anyone done or knows how to do it.
>
> I am using an LPC2294 demo board with CAN drivers.
>
RS485 is an physical spec, CAN has a different physical spec and
specifies a packet protocol as well, complete with addressing and
arbitration mechanisms.
What you seem to be asking for would be 'very, very difficult',
(trying not to use the 'i' word).
Rgds,
Martin
Reply by ●November 23, 20072007-11-23
jdauchot Wrote
>Can the CAN ports on the LPC2200 be configured to be used as RS485
>ports?
If you mean make them behave like a standard asynchronous serial port over
RS485 then I don't see how that would be possible. I don't see a way of
perverting the framing to match 232 type signalling, especially once you
throw in bit-stuffing.
If you mean could you use RS485 drivers for the bus but use CAN framing
then yes. That's how the original CAN networks were built. But with real
CAN drivers widely available that seems pointless.
Robert
--------------------------------
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>Can the CAN ports on the LPC2200 be configured to be used as RS485
>ports?
If you mean make them behave like a standard asynchronous serial port over
RS485 then I don't see how that would be possible. I don't see a way of
perverting the framing to match 232 type signalling, especially once you
throw in bit-stuffing.
If you mean could you use RS485 drivers for the bus but use CAN framing
then yes. That's how the original CAN networks were built. But with real
CAN drivers widely available that seems pointless.
Robert
--------------------------------
mail2web.com Enhanced email for the mobile individual based on Microsoft
Exchange - http://link.mail2web.com/Personal/EnhancedEmail
Reply by ●November 24, 20072007-11-24
jdauchot wrote:
> Hi All
>
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
>
As Robert mentioned yes.
Physical Level = RS485 transceiver
Framing/Arbitration = CAN bus.
This part is suitable for the job, and the data sheet includes CAN pin outs:
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1017,P1713
Joel
> Hi All
>
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
>
As Robert mentioned yes.
Physical Level = RS485 transceiver
Framing/Arbitration = CAN bus.
This part is suitable for the job, and the data sheet includes CAN pin outs:
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1017,P1713
Joel
Reply by ●November 24, 20072007-11-24
I think CAN and RS-485 physical layers are a bit different. The main
difference is that CAN arbitration is based on multiple transceivers
sending at the same time, with RS-485 you try to avoid multiple
transceivers sending at the same time as much as possible. Somebody
correct me if i'm wrong here...
And why would you want to use RS-485 transceivers with a CAN controller
anyway?
Regards,
Richard.
jdauchot wrote:
> Hi All
>
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
>
> If so has anyone done or knows how to do it.
>
> I am using an LPC2294 demo board with CAN drivers.
> Regards
>
> Jean-Jacques
>
>
difference is that CAN arbitration is based on multiple transceivers
sending at the same time, with RS-485 you try to avoid multiple
transceivers sending at the same time as much as possible. Somebody
correct me if i'm wrong here...
And why would you want to use RS-485 transceivers with a CAN controller
anyway?
Regards,
Richard.
jdauchot wrote:
> Hi All
>
> Can the CAN ports on the LPC2200 be configured to be used as RS485
> ports?
>
> If so has anyone done or knows how to do it.
>
> I am using an LPC2294 demo board with CAN drivers.
> Regards
>
> Jean-Jacques
>
>
Reply by ●November 25, 20072007-11-25
Richard Duits wrote:
> I think CAN and RS-485 physical layers are a bit different. The main
> difference is that CAN arbitration is based on multiple transceivers
> sending at the same time, with RS-485 you try to avoid multiple
> transceivers sending at the same time as much as possible. Somebody
> correct me if i'm wrong here...
>
> And why would you want to use RS-485 transceivers with a CAN controller
> anyway?
>
Primarily flexible wiring topologies. This combined with:
1. Offload fault tolerance to silicon and minimize interrupts to CPU.
2. Silicon handles arbitration.
3. Prioritized messaging.
Using RS485 transceivers with Lonwork Nueron chips is pretty common as well.
Joel Winarske
> I think CAN and RS-485 physical layers are a bit different. The main
> difference is that CAN arbitration is based on multiple transceivers
> sending at the same time, with RS-485 you try to avoid multiple
> transceivers sending at the same time as much as possible. Somebody
> correct me if i'm wrong here...
>
> And why would you want to use RS-485 transceivers with a CAN controller
> anyway?
>
Primarily flexible wiring topologies. This combined with:
1. Offload fault tolerance to silicon and minimize interrupts to CPU.
2. Silicon handles arbitration.
3. Prioritized messaging.
Using RS485 transceivers with Lonwork Nueron chips is pretty common as well.
Joel Winarske
Reply by ●November 25, 20072007-11-25
Joel Winarske wrote:
> Primarily flexible wiring topologies. This combined with:
> 1. Offload fault tolerance to silicon and minimize interrupts to CPU.
> 2. Silicon handles arbitration.
> 3. Prioritized messaging.
>
You can get all this with CAN transceivers too.
> Using RS485 transceivers with Lonwork Nueron chips is pretty common as well.
>
>
Don't know Lonwork Nueron.
Regards,
Richard.
> Primarily flexible wiring topologies. This combined with:
> 1. Offload fault tolerance to silicon and minimize interrupts to CPU.
> 2. Silicon handles arbitration.
> 3. Prioritized messaging.
>
You can get all this with CAN transceivers too.
> Using RS485 transceivers with Lonwork Nueron chips is pretty common as well.
>
>
Don't know Lonwork Nueron.
Regards,
Richard.
Reply by ●November 25, 20072007-11-25
> You can get all this with CAN transceivers too.
>
Not so much the flexible wiring topology.
>>
>>
> Don't know Lonwork Nueron.
>
It's an off shoot of Apple Talk targeting building automation and such.
http://www.echelon.com/developers/lonworks/neuron.htm
Joel
>
Not so much the flexible wiring topology.
>>
>>
> Don't know Lonwork Nueron.
>
It's an off shoot of Apple Talk targeting building automation and such.
http://www.echelon.com/developers/lonworks/neuron.htm
Joel
Reply by ●November 25, 20072007-11-25
Joel Winarske wrote:
>> You can get all this with CAN transceivers too.
>>
>>
>
> Not so much the flexible wiring topology.
>
>
When we wire our CAN nodes together we do not pay much attention to
network topology and it always seems to work. We have had networks with
up to about 100 nodes. Most important is to limit the slew rate for the
CAN driver (the latest NXP CAN transceivers do this automatically). This
will limit the reflections on the network even if your network is not
the ideal bus topology.
Regards,
Richard.
>> You can get all this with CAN transceivers too.
>>
>>
>
> Not so much the flexible wiring topology.
>
>
When we wire our CAN nodes together we do not pay much attention to
network topology and it always seems to work. We have had networks with
up to about 100 nodes. Most important is to limit the slew rate for the
CAN driver (the latest NXP CAN transceivers do this automatically). This
will limit the reflections on the network even if your network is not
the ideal bus topology.
Regards,
Richard.
