AVR-Chat

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Ned Konz
Sent: 17 September 2009 10:08
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] CAN Bus - usefull for long distances of outdoor
cable?

On Sep 5, 2009, at 11:15 AM, Chuck Hackett wrote:

>CAN is also used in much larger environments (chemical plants, 
>semiconductor fabs, etc.).



Is even recognised now for aviation, such is the robustness of the standard.


>If you're thinking about using CAN you want to also use a CAN physical 
>layer (for robustness).



I would opt to use on the many CAN physical devices out there. If the AVR
you use does not have it built in, then look at the Microchip MCP2510 as
this interfaces easily to the AVR using SPI bus.


>Should be.
>
>Message priority in CAN is handled by the message itself: that is, the 
>actual message, taken as a number, is its own priority. So you have 
>quite a bit of flexibility (though existing CAN schemes like CANopen, 
>DeviceNet, etc. have their own meaning attached to various bits within 
>the CAN messages).



Once you have used CAN for control you won't go back so easily to the likes
of RS485 and its inherent master/slave operation. With the mult-master in
the CAN bus you can concentrate on sending or receiving data instead of
working out who is going to play master. Adding new nodes to send additional
data does not require an update to any other device unless it is going to
act on that data.

In fact, I used to have a weather station and a boiler control system
running in my old house all on the same CAN bus network. I built the weather
station first then add the boiler control. It basically operated independent
of the weather station but it used the data from the outside temp sensor to
control the heating level. I didn't have to make any changes to the weather
station nodes and simply added the boiler nodes into the network. They then
sent data on the bus which the required boiler nodes would receive and
process.


-- 
Ned Konz
Seattle, WA
360-629-1091
http://bike-nomad.com



[Non-text portions of this message have been removed]