Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
I understand about SDO's, have sent them to a module (Maxon Epos motor
I have used them to read/write register entries from the Object
dictionairy successfulley.
Have used this site as reference as well;
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

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
, 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?


Re: CANopen PDO

Quoted text here. Click to load it

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

Quoted text here. Click to load it

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

orbitersim wrote:
Quoted text here. Click to load it

Quoted text here. Click to load it

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
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( offers a nice PDO configuration
window as shown in
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

Site Timeline