[time-nuts] Form factor

Chris Albertson albertson.chris at gmail.com
Wed Dec 22 23:03:18 UTC 2010


On Wed, Dec 22, 2010 at 2:41 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> In message <AANLkTikLKD2Z15kwbPEwXTFGFf=wqWsiNv+To7OuPf61 at mail.gmail.com>, Chri
> s Albertson writes:
>
>>Can "CAN" do this?
>
> CANbus is mostly intented for hostile environments, and for anything
> "in-box" less can do.
>
> The problem with I2C is that it is not well suited for systems with
> more than one master on the bus.  It can be done, but it's messy.
>
> MODBUS is also an option.

Quick reading says that MODBUS allows only one master unless the
physical media is TCP/IP over Ethernet.  I don't think we want
something that complex.

How hard is it to do multi-master I2C.   I still like I2C because it
can be doe on the smallest of uP with zero extra hardware.   But
something else might be better.

If I try to make a prototype I2C multi-master system what are some
problems I should look out for.

I think prototypes or simulations are the way to decide this.  Seems
we are not going to know which is best for this purpose without taking
each proposal to the next level of design detail

Maybe we should have a budget in square mm and dollars for bus
interface  would be good to say "100 mm^2 and $2. but I don't know
what's realisticMaybe use those numbers as a figure of merit when
comparing two designs
-- 
=====
Chris Albertson
Redondo Beach, California



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