Re: CANOpen Object Dictionary Help

Hi John;

One thing that you should realize is that CAN and CANopen aren't exactly 
the same thing.  CAN is a type of low level serial bus which supports 
sending messages containing up to 8 bytes of data at a time.  Lots of 
microcontrollers have CAN peripherals built in. CANopen is a higher 
level protocol built on top of the CAN bus. It's popular in industrial 
applications.

You may not even need to worry about the CANopen protocol unless you're 
trying to interface to a device that implements it.  If your small 
project just involves communicating between a couple devices that you 
will be writing the software for, then you can just send CAN messages 
back and forth between them.  If you're trying to interface to a device 
that talks CANopen then you will need to implement that protocol.

In CANopen, the main way that you communicate with a device is by 
reading / writing parameters on the device.  These parameters are called 
'objects' in CANopen, and the set of all the objects that the device 
supports is called the object dictionary.  CANopen defines a couple 
different ways to read and write these objects by sending specially 
formatted CAN messages.

If you're interested in implementing CANopen on your device, you should 
download the CiA 301 specification from here:
http://www.can-cia.org/

That's the spec that defines the basic methods for reading / writing 
objects using CAN messages.

Rgds,
Steve

On 06/11/2014 07:24 AM, Spam Spam wrote:
> Hi all,
>
> I am new to CAN and am using it  for a small project I'm doing. I was 
> wondering what the use of the object dictionary in CANOpen is. I am 
> very sorry if this sounds basic, but I have thoroughly searched google 
> and have come up with nothing that can explain to me clearly the use 
> of the object dictionary and if/how I can implement it on my own. I 
> was wondering if there are alternatives to CANOpen/if I really needed 
> the object dictionary as all I am doing is communication using CAN.
>
> Thanks you very much for your help,
> John