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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: Re:Positional/physical addressing
Date: Tue, 24 Jun 2025 20:18:36 +0200
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On 6/24/25 19:05, Don Y wrote:
> On 6/24/2025 9:49 AM, Don Y wrote:
>> On 6/24/2025 9:18 AM, Martin Rid wrote:
>>> CAN network?
>>
>> Each CAN node either needs a unique address to which messages can be
>> directed;  *or*, to KNOW to listen for particular BROADCAST messages.
>>
>> So, you either send a message to node 5 to do something
>> OR, you send a message about that something and expect
>> that node to know that *it* should process that message.
>>
>> If all of the nodes are *identical* (hardware and software),
>> there is nothing to distinguish one device from any other.
> 
> By way of example, in the 70's, we would do "poor man's networking"
> by daisy-chaining IDENTICAL devices with serial ports:
> 
> HOST---->[]----->[]---->[]----->[]
> 
> (each set of brackets represents a device with its serial input
> on the left side and output on the right)
> 
> If I pass a message (from the host) of the form "1xxxxxx", the
> first device receives the message, notices that it begins with
> a '1' and assumes it is meant for it; the message is absorbed
> by that device.

WS2812 LED chips do something like that. The first chip in the chain
absorbs the first three bytes and passes on all that come after, and
so on down the chain. Wait 50 us and the first chip in the chain is
ready again to intercept its three bytes.

It's common for driving LED strips.

Jeroen Belleman