Re: Positional/physical addressing

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.

That programs each device with an unique address and the rest can be
done with normal digital handshaking and read/write.  It is a way of
overcoming the 'identicality' of the devices so you don't have to
allocate individual serial numbers to them during manufacture, which
could reduce the cost if a lot have to be made.

That's the goal.  Having to "program" a unique serial number
is an added labor step and tracking issue.
If, OTOH, the manufacturer of a component (e.g., the Dallas serial
number chip that Dennis mentioned -- or, the MCU itself!) could
make that guarantee, then there would be no need to track
which S/Ns have been assigned, to date.

Then they can all be strung out along a two-wire bus (send and return)
to allow individual devices to be removed or changed without a lot of
re-wiring or bridging connectors, so installation and maintenance costs
are reduced too..

The goal is for the end user to be able to change out these devices
(or, install them) just like replacing light bulbs.  You don't want
to have to dispatch paid staff to replace an item that costs pennies!
The semiconductor components are unlikely to need replacement.
But, there are mechanisms involved to provide the haptic feedback.
How long those are likely to remain viable in extended service
(decades) is something with which I wouldn't want to gamble.
[It's relatively easy making devices that have short lifespans
or can be "returned to the place of purchase".  A lot harder
to address things like the physical plant in a residence, etc.]