Re: Ethernet Boards

[Kevin Hawkins <lists@xxxxxxxxxxxxxxxxx>]

Robert Welsh wrote:

>>Take a look at the Rabbit boards too - the dev kits come with
>>the C development software and are fairly fast and have large
>>amounts of RAM / Flash.   I use them in the xAP to C-Bus gateway.
>>[..]
>>http://www.rabbitsemiconductor.com/
>>
>>
>>
>
>What's the downsides to Rabbit, Kevin ?
>
>Taking a look at the site, you're right, the basic board is rather
cheap
>($55 for the RCM2250).
>
>However, as a total new-guy to this stuff, I'm correct in saying that
I'd
>need to create a PCB with power etc when I get past the point of using
the
>prototype board? I couldn't see anything of that nature on the Rabbit
>website - which, is entirely possible, as I assume you're
likely/supposed to
>have stuff other than just power (e.g user control inputs) on your
mainboard
>(ie it'll be mothered to something application specific)
>
>

Yes, the Rabbit is a 'core' meaning you normally plonk it into another
pcb in production. Some of the Rabbits use standard .1" connectors and
some use more dense connectors that are more expensive and awkward to
source. The .1" of course would fit veroboard or the plug in
breadboard
type prototyping systems.  The 'core' has a lot of inbuilt I/O pins so
you don't need to add circuitry for these unless of course you have
level shifting, isolation or protection circuitry to add. Often however
you will need to add the latter. Yes you need to add power of course and
some units are 3.3V but have TTL compatible tolerance. If you are
wanting true RS232 level I/O then you need to add the ubiquotous Maxim
chip but you may be happy with 5V serial data which is inbuilt.  In a
real 'hack' situation I guess you could have wires just coming of a
.1"
header cable supplying power etc.   I am unfortunately not at the low
level of component integration that Ian can achieve - basically I just
don't have the skills or patience (or eyesight !) to do it anymore.
However it is obviously technically the most flexible route to go.

I am now very fond of the Rabbits (after a steep learning curve for me
in C) - I have some issues with the way Rabbit handle updates to the C
complier and also some software modules are extra and chargeable, should
you need them.  Reprogramming devices over Ethernet I believe is still
an extra cost for example. There is a very knowledgeable support list
for Rabbit which is a great plus.

I am not sure what I/O functionality you would be looking for in your
design, perhaps I missed an earlier thread..   What do you need onboard ?

There are a couple of very basic I/O boards for Rabbit processors - and
I guess even my board might be useful to some, if so I would happily
make that available, indeed I have sold a couple just for taht purpose.
It has 4 RS232 serial ports and all the I/O brought to an IDC edge
connector and onboard power circuitry (uses the 3700 family)  It also
has  matrix keypad support and  some basic lcd circuitry. The parallel
I/O is straight to Rabbit pins however so not protected in any way.

>The Ethernut board (I hate to go back to it - it's just that what I've
been
>reading about over the weekend) has all that already on the PCB - but
it's
>more expensive because of that.
>
>

I think a lot of teh onboard I/O on that board is much teh same as a
Rabbit - ie signlas just brought to an edge connector. It does have teh
psu regulation on board though. £100 vs say £40 for a Rabbit and £40
for  a custom and appropriate daughter board might make sense though.
How many units are you building ??

>Rob
>
>
>
I would mention also there are some very capable designs built around
the Basic Stamp (Milford Instruments) , or the Scenix  BasicX processor
board and even the Siteplayer plus the CoBox/XPort designs from
Lantronix..  What would your preferred development environment be
(assembler / C / high level eg Basic) >>?? Those earlier boards don't
have Ethernet but could maybe be data collection or I/O handlers into a
serial port on a Rabbit.

Kevin