AVR-Chat

The CAN controller in the device needs a fair bit of work to fully
understand it and also a good understanding of CAN to be able to use it
fully.

 

There is quite a bit to setup the device to make it work and it took me
about 1 week with the code from the Atmel website, porting it to the
Codevision compiler before it would work. It is ready to go with the WinAVR
I believe so if you have that compiler, you should be able to figure it out?
I was already familiar with the Microchip MCP2515 before but moving to the
AVR CAN took me a whilst to figure out and I am still working on it.

 

CAN does not work as a request and get data, except for certain situation
where you do a request. Normally, CAN devices just send data on event or at
preset times. For the likes of digital inputs, I would only send a message
on the bus if there was a change. For analog I would send at a preset rate.

 

The beauty of CAN is that you don't have to worry about having a master with
multiple slaves as you would with the likes of RS485. You simple ensure that
each device on the bus sends a unique ID for each message. CAN messages are
based on priority so a higher priority message goes first if 2 devices try
to send data at the same time. This reduces your workload in the processor
to very little and you simple set the buffer to transmit and let the CAN
controller do the work of sending the message and detecting errors.

 

Remember that CAN is source message based. That means there is no
destination address. The remote devices know which messages they are
interested in and are usually setup with the message filters to only receive
those messages. This bit takes a fair bit of work to understand but once you
do, it will be easy to create remote devices listening only for required
messages.

 

Which compiler are you using?

 

Dave.

 

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of blue_eagle74
Sent: 31 December 2009 10:37
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Re: 90can128 can controller

 

  

I have searched and searched but cant find what I need. Can anyone provide a
simple C code in CV using the CANbus. A simple one for transmit and/or
request info from the other AVR. I just want to talk to another AVR and have
it respond and turn on an LED so I can see that it works.

I have found code but dont understand it. Does anyone have a tutorial?

Brian



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