CANopen PDO

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I understand about SDO's, have sent them to a module (Maxon Epos motor
control).
I have used them to read/write register entries from the Object
dictionairy successfulley.
Have used this site as reference as well;
http://atlas.web.cern.ch/Atlas/GROUPS/DAQTRIG/DCS/LMB/PROFILE/cano-sdo.htm
By sdo's I can fully control the node, but it creates lots of traffic
over the bus and I have to keep polling to read for example the
statusword.


However, I do not completely understand about PDO's.
What I'd like to know, is how I can make the CAN Node automaticly send
a PDO containing a certain value obtained from one of the specified
address in for example the 1st Mapped Object in TxPDO 1 ?

When I look in the Node's Object dictionairy, I can see that the Pdo
transmission type is set to 0xFF, which is 255, and according to this
site:
http://atlas.web.cern.ch/Atlas/GROUPS/DAQTRIG/DCS/LMB/PROFILE/cano-pdo.htm
, it is asynchronous, device profile specific event, which seems to be
correct to me.

Do I need to send something first in order to let the Node send
automaticly some of its input values when they change?

regards


Re: CANopen PDO

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That depends on your node. In the description of your node should be
stated what it can map.

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CANopen nodes usually are in "preoperational state" on start-up.
The CANopen master or you has to switch it to operational state.
Sending something with identifier 0 ( zero ) will do it, but I can't
remember the exact message format right now.


Re: CANopen PDO
Note: biased answer as we earn some money with the prodicts
mentioned...

orbitersim wrote:
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motor


send
http://atlas.web.cern.ch/Atlas/GROUPS/DAQTRIG/DCS/LMB/PROFILE/cano-pdo.htm
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be


To set a node into the operational state the NMT (Network Management)
master needs to transmit the "all node switch to operational" message:
CAN-ID: zero, 2 data bytes: 01h 00h

See chapter 2.8 "Contents of CANopen Messages" in www.CANopenBook.com
for additional info about message contents.

Once a node is operational the PDOs of type 255 will be transmitted
whenever their data changes.


Which tool do you use to configure your nodes?
CANopen Magic Pro(www.CANopenMagic.com) offers a nice PDO configuration
window as shown in
http://www.canopenmagic.com/peak/images/pcomp_scr_pdocfg.gif
In this example the gree fileds indicate the PDO mapping (which Object
Dictionary entries are mapped to the PDO), the white fields the
communication parameters. Here the Event Time of 333 indicates that
this PDO is transmitted every 333ms.
Olaf, Tutor at ESAcademy
www.canopenbook.com
www.canopenmagic.com


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