| Author |
Message |
orbitersim
Guest
|
 Posted:
Mon Dec 20, 2004 8:02 pm Post subject:
CANopen PDO |
|
|
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 |
|
| Back to top |
|
 |
Peter Scholz
Guest
|
| Posted:
Tue Dec 21, 2004 1:56 pm Post subject:
Re: CANopen PDO |
|
|
orbitersim wrote:
| Quote: | ...
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 ?
|
That depends on your node. In the description of your node should be
stated what it can map.
| Quote: | ...
Do I need to send something first in order to let the Node send
automaticly some of its input values when they change?
|
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. |
|
| Back to top |
|
|
Tutor at ESAcademy
Guest
|
| Posted:
Mon Jan 03, 2005 10:06 pm Post subject:
Re: CANopen PDO |
|
|
Note: biased answer as we earn some money with the prodicts
mentioned...
orbitersim wrote:
| Quote: | I understand about SDO's, have sent them to a module (Maxon Epos
motor
control).
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?
|
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 |
|
| Back to top |
|
|
|
|
|
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in