Re: Rabbit vs. AVR

[ian.bird@xxxxxxxxxxxxxxxxxxxxxxx]

Hi Andy

I am indeed a convert to the AVR but from the PIC not Rabbit

I know quite a few people using the Rabbit and all seem pretty happy with
them but at the same time they are doing relatively lightweight things. I
read somewhere that Rabbits are poor on timing ability - read into this
what you will as I don't know exactly what they were referring to. I think
at the time the conversation was about timers on the AVR and Rabbit. The
AVR is well endowed in this area and this was the conclusion of the
discussion.

The JTAG ICE is a stunner for debugging your programs and the latest
version of the AVR Studio fixes a lot of the problems I was having with it,
- great tool. There is also the STK500 and STK501 which enable you to
prototype the smt Mega64/128 without actually soldering it. These work well
although I never managed to get I2C working on it. Works fine on my dev
board though.

I think the setup cost for Rabbit is less and it has Ethernet out of the
box. It will always need some sort of add on board (PCB) to make your
project come to life as Dave says.

As for the AVR, again you will need a PCB making to make the most of it so
no real difference there. I have learnt a lot of tricks for making and
soldering smt boards and components. In truth if you get adventurous you
cannot avoid smt as some chips are only available in this package - it's
just a matter of time. If you want to know more then ask away.

PCB's - you can get these made for 21 or 26 dollars (single or double
sided) over the Web although I have not tried them out yet but I plan to
soon (hopefully). At this sort of cost it is hardly worth doing your own
unless you make as many mistakes as I do ;-).
http://www.olimex.com/pcb/index.html

It is best to get some sort of PCB design software in the future as this
helps a lot with the creation of you project. There is a host of packages
available from truly crap to stunning. Prices follow the same range i.e.
shareware to more than I can afford in several years of working.

I have Ethernet on AVR working a treat although not hammered just yet. I am
happy to share designs etc. but you would need to buy the source code
rights ($150) from the writers in order to share these.

I went for the AVR because of the versatility of making my own packages and
design up without limitations. My current project would not be possible in
the way I am planning it with a Rabbit simply because of the Rabbit board
layout. As for complex abilities - I am making a graphic display with touch
screen, several touch sensitive buttons, Ethernet ability, several external
EEPROM chips, external RAM and sensors including temperature, humidity and
a light sensor with a human eye response curve. All this should operate in
real time with no noticeable delays to the user. Pretty impressive for a
128k chip. I guess this is a pretty advanced project and has taken me a
while to get to where I am. A lot of the code can be shared as I wrote it
e.g. the graphic display driver, I2C driver etc.

Finally I am very impressed with the CodeVision compiler and the support
its author offers. Excellent all round with good pricing to boot.
http://www.hpinfotech.ro/

Ask away if you have more questions - on or off list, no problems.

Ian




---------+------------------------------>
Dave McLaughlin
<dave@xxxxxxx
ipse.co.uk>

27/11/2004 12:14
Please respond to
ukha_d

---------+------------------------------>
>-----------------------------------------------------------------------------------------------------------------------------

To:       ukha_d@xxxxxxx
cc:       (bcc: Ian Bird/CV/Novartis)
Subject:  Re: [ukha_d] Rabbit vs. AVR
>-----------------------------------------------------------------------------------------------------------------------------





Hi Andy,

Depends on what you want to use the devices for. The AVR devices are
great if you want a simple interface and no Ethernet, such as working
with RS485, CAN , RS232 etc. The cost of the Rabbit modules are much
higher than an AVR device. You still need to build a PCB for both if you
are doing your own design. This is always the case with the Rabbit Core
Modules as they are not standalone boards and require power etc.

Your initial costs of getting on the AVR trail is the development tools
but once you have these, they suit all future projects too, much the
same as the Rabbit. One tool I would suggest you get is the JTAGICE for
in circuit debugging. If after using the Rabbit and having the ability
to debug your code by setting breakpoints and stepping through the code,
you will be at a loss without this capability. It will also take longer
to figure out what is happening in your code without one. Ask Ian Bird,
he is a convert on the AVR and an expert with the JTAGICE now. Right
Ian?  :o)

For Ethernet, the Rabbit is your best bet. All the hardware and
libraries are done and the larger code space in the Rabbit makes it
easier to do larger projects. The largest AVR at present is only 128K of
Flash so a wee bit limited on the same as the Rabbit with up to 512K of
flash. That is not to say that the AVR won't do what you want, it all
depends on the needs of your project.

I happily use both alongside each other on my CAN bus network. The AVR
devices handle all the simple IO etc and the Rabbit is used (or will be
when completed) as a touch screen interface to it all.

As for the SMD side of things, there are some excellent ready built
boards out there that you can use (check on AVR freaks under tools).
Nearly all of then have 0.1" pins you can connect to which is easier
to
make a PCB for than SMD. Saying that, even the 128K ATMega128 is not too
difficult to solder onto a board. All you need is a steady hand, a fine
tip soldering iron and some solder braid to clean up any pins you
accidentally soldered together. A bit of practice and you can do them
without thinking about it :o)

If you have any more questions, give me a shout.

Regards
Dave...

---
Very funny Scotty, now beam down my clothes!!
---
http://www.v8carlton.com
http://www.embeddedcomputer.co.uk
---



UKHA wrote:

> Hi,
>
> I've been looking to improve my electronics capabilities (yet again)
> and have noticed a lot of you here use AVR stuff. I've been working
> with Rabbit RCM 2200's but wanted to know what one gives over the
other.
>
> I've had a look around and concluded (perhaps wrongly)  that anything
> that I want to have an ethernet network connection should probably go
> on a Rabbit since the cost appears so much lower. It just seems to me
> that there are a lot of people who rave about the AVR stuff, and I
> don't know enough about them to make a real decision as to what's
> better for me. I do see that the AVR stuff seems to all be surface
> mount, which is a big minus in my book (soldering skills are limited).
> I've taken a look at avrfreaks but there's just way too much
> information there to be of any real use to me (or I guess anyone
> starting out)...
>
> Has anyone got/used both the rabbit series and AVR? Any comparisons or
> opinions?
>
>
> Thanks
>
> Andy
>
>
>
>
>
>
>
>
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