Re: [Embedlets-dev] Enterprise Outpost 'Wide fanout' pattern diagram

[Gregg G. W. <gr...@sk...>]

>The reason I am interested in this issue is that my vision for how I think an
>Enterprise Outpost should work includes using a standardized 'intelligent'
>serial bus for I/O expansion (either SPI or I2C).  If a network protocol could
>be standardized for these expansion modules, and if their connector and
>electrical interfaces were also standardized, then the expansion modules and
>driver software could be used with almost any kind of Outpost implementation,
>not just a TStik.
>
>The 'intelligent' part of the bus indicates that since many of the the I/O
>modules are microcontrollers, then the bus could be used as a multimaster
>collaborative network which should be able to ease the processing burden on the
>main controller.
>
>Does anyone have any ideas on what kind of protocols would be good to use for
>an intelligent expansion bus like this?

What we have been doing in our projects is just not trying to simplify this
issue.  In most of our projects, there is only one reasonably close to
standard two way comms protocol that goes over serial, and that is MODBUS.
If we have devices that do MODBUS, we have tools ready to apply.  If not,
then we just bill for custom development.  This pushes customers towards
standards to some degree.

This will be the hard part about any new protocol.  It has to appear at the
I/O point source first.  Then the backend support can be provided for it, and
eventually, we can push customers and vendors both towards adoption.  But,
even modbus has problems with adoption because of hard limits on sizes.

We need to try and separate the actual application protocol from the
transport choices.  The protocol must provide a version number as a
base so that it can be enhanced.  But, more than that, it should have
some compartmentalization that allows optional parts to be specified.

This might allow for signatures, encryption, routing (fan out control), QOS
and other necessities to be optional so that minimal bandwidth could
be achieved for each application.  Bandwidth will become an issue,
no matter what the transport media is, believe me.

-----
gr...@cy...  (Cyte Technologies Inc)