Re: Positional/physical addressing

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Sujet : Re: Positional/physical addressing
De : blockedofcourse (at) *nospam* foo.invalid (Don Y)
Groupes : sci.electronics.design
Date : 25. Jun 2025, 10:14:28
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <103gem6$2lhen$2@dont-email.me>
References : 1 2
User-Agent : Mozilla Thunderbird
On 6/25/2025 1:52 AM, Liz Tuddenham wrote:
Don Y <blockedofcourse@foo.invalid> wrote:
 
I have a large group (hundreds) of switches and displays.
Their state needs to be determined/updated rather slowly
(a few hertz).  Each has local smarts so it can retain
some state information and processing capability.
>
Their physical arrangement varies from one installation to
the next.  So, there is no economy of scale available by
"settling" on a specific configuration or physical arrangement.
>
I would like to be able to address them (the entire *set*) -- and
pass data to/fro -- with a small, fixed number of conductors /having
built them all identically/.  The amount of data exchanged being
traded off vs.  update rate for a given interface bandwidth.
>
The obvious "one wire" scheme would have a gazinta and cumzouta
for each device so the device could modify a serial bit stream
to account for its "position" in that stream.
>
I can pipeline processing between devices so the overall access
rate remains high (though latency obviously suffers).
>
But, a single device failure renders all downwind devices
inaccessible (or, possibly ALL devices, depending on implementation)
>
I'm looking at a two wire solution that piggybacks the data
stream on power and ground (those "two wires").  But, it
adds complexity to the devices (I want to keep them REALLY
small and dirt cheap)
>
Any existing schemes that allow this without the failure mode cited?
 Philips I2c  ?
Again, the devices would need unique addresses to be individually
addressable.  If you want them to be *identical*, then this
contraindicates unique addresses.
Imagine buying ethernet adapters where they were all truly identical.
I.e., each had the exact same MAC address!  How could you use them
(without resorting to a star topology that assigned meaning to
each arm of the star)?
There have been numerous "hacks" to allow identical devices to
coexist and remain individually addressable.  But, all rely on
making the "uniqueness" part of some external interconnect.
E.g., a trick I use for addressing plug-in modules is to
run, for example, two "select lines" to each "slot".
The module will respond if it sees both lines "low"
(for example -- or, some other CONSISTENT combination).
I run the two select OUTPUTS (from controller) to the first
slot.  Then, invert one of them and swap it with the other
when running it to the next slot.  Then, repeat the process
again.  And again.
This results in each slot seeing (for example, invert lsb then swap):
Controller    1    2    3    4
00           00   10   11   01
01           01   00   10   11
10           10   11   01   00
11           11   01   00   10
[assuming I haven't f*cked things up in my head while typing this]
You can see that only one slot ends up with the necessary "00"
to enable selection.
But, this requires "logic" in the interconnect fabric.  My goal
is just to "run wires" between devices and let the devices sort
it all out.

Date Sujet#  Auteur
24 Jun 25 * Positional/physical addressing25Don Y
24 Jun 25 +* Re: Positional/physical addressing8Martin Rid
24 Jun 25 i`* Re: Positional/physical addressing7Don Y
24 Jun 25 i `* Re: Positional/physical addressing6Don Y
24 Jun 25 i  +* Re: Positional/physical addressing4Jeroen Belleman
25 Jun18:30 i  i`* Re: Positional/physical addressing3Ian
25 Jun18:43 i  i +- Re: Positional/physical addressing1Don Y
25 Jun22:29 i  i `- Re: Positional/physical addressing1Jeroen Belleman
24 Jun 25 i  `- Re: Positional/physical addressing1Don Y
25 Jun09:52 +* Re: Positional/physical addressing11Liz Tuddenham
25 Jun10:14 i`* Re: Positional/physical addressing10Don Y
25 Jun11:14 i `* Re: Positional/physical addressing9Liz Tuddenham
25 Jun18:04 i  `* Re: Positional/physical addressing8Don Y
26 Jun09:59 i   +* Re: Positional/physical addressing4Liz Tuddenham
26 Jun10:46 i   i`* Re: Positional/physical addressing3Don Y
26 Jun17:53 i   i `* Re: Positional/physical addressing2Liz Tuddenham
26 Jun21:48 i   i  `- Re: Positional/physical addressing1Don Y
26 Jun20:58 i   +* Re: Positional/physical addressing2bitrex
26 Jun21:50 i   i`- Re: Positional/physical addressing1Don Y
26 Jun21:00 i   `- Re: Positional/physical addressing1bitrex
25 Jun18:40 +* Re: Positional/physical addressing4Ian
25 Jun20:41 i`* Re: Positional/physical addressing3Don Y
25 Jun21:35 i `* Re: Positional/physical addressing2Dennis
25 Jun22:53 i  `- Re: Positional/physical addressing1Don Y
25 Jun19:25 `- Re: Positional/physical addressing1john larkin

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