Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Positional/physical addressing
Date: Thu, 26 Jun 2025 13:48:01 -0700
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On 6/26/2025 9:53 AM, Liz Tuddenham wrote:
> Don Y <blockedofcourse@foo.invalid> wrote:
> 
>> On 6/26/2025 1:59 AM, Liz Tuddenham wrote:
>>>> This is too "high tech".  You're effectively trying to build a TDR into
>>>> each device.  Recall, I want these to be dirt cheap because I use so
>>>> many of them in a system.
>>>
>>> Actually the individual devices just need to store the time between two
>>> clear digital pulses as a number.  If the devices are never closer than
>>> one yard apart, a 300 Mc/s clock speed will be sufficient to distinguish
>>> between them.  (The twin identification pulses will be spaced by double
>>> the path length.)
>>
>> Sorry, this is a *display*.  Even as oversized as it is (a few
>> square feet), it is quite possible that devices will be immediately
>> adjacent -- a fraction of an inch apart.
> 
> I hadn't realised they were that close together.  Obviously my
> suggestion fir timing is a non-starter.

There are a *lot* of them (hundreds).  So, I have to try to
pack them as densely as possible.

The best analogy would be the "activity indicators" on
network switches; they exist so you can visually identify
ports that are active, inactive, failed, etc.  A simple
glance is usually enough to spot anomalies.

Now, add to that, being able to make this determination
with your eyes closed.