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Re: Identification of modules

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On 3/31/2017 12:21 AM, Piotr Wyderski wrote:
> My system will be composed of a number of free slots
> which can be populated with some modules (mostly
> containing power electronics). The simplest the module
> is, the better, don't want to use a micro to do the
> job because of its limited FLASH/EEPROM retention time.

Retention *time*?  What sort of product lifespan are you
assuming?

> The module must be able to report its identity to the
> main controller (one from the closed universe of, say,
> 32 possibilities known in advance) and which slot it
> occupies. A very useful feature would be to have
> a temperature sensor of some kind for moderate overload
> detection.

Do you want slots to be wired (nearly) identical?  Or,
are you willing to have a "controller slot", etc.?

> I cannot afford many pins to do that, so the simplest
> 5+5 pin solution of binary encoding the relevant
> information is not an option.
>
> I came up with the idea to (ab)use the Maxim's DS2438
> battery monitor and use its voltage/current sensor A/D
> channels to fetch the value encoded by a resistive divider.
> The temperature sensor is there for free and the cost is
> below a buck for 20 pieces in China. It supports the 1-wire
> bus.
>
> Do you know anything simpler/better or is there
> anything to worry about that Maxim part?

Sole source?

> BTW, why are the Maxim parts so insanely expensive?
> I could find many applications for the 1-wire DS2450
> A/D converter, but the cost makes it pointless -- one
> can emulate it with any SO8 micro for 1/4 of its price.

What's wrong with using a tiny MCU to determine which
slot *it* resides in and then convey its slot number and
"module type" to the controller, regardless of where the
controller happens to be located?

Apply Vref to the "slotID" pin of the leftmost slot
and GND to the same pin on the rightmost slot.  Put
a fixed resistance between the slotID pin on each slot
and the slot to its right.  MCU on the card *in* the
slot can then read the voltage on the slotID pin to
identify itself.

Alternately, put a unique R value between Vref and
each slot's slotID pin then sense this (with a current
sink, RC oscillator, etc.).

[You can also do this with actives -- at a higher cost]

Another pin can act as a bidirectional bus that the
controller assumes ownership of and polls the individual
MCU's on each slot.

Of course, this assumes you are taking precautions to
protect all inputs that are "exposed" on the backplane...

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Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 09:21 +0200
  Re: Identification of modules Don Y <blockedofcourse@foo.invalid> - 2017-03-31 01:31 -0700
    Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 10:36 +0200
      Re: Identification of modules Don Y <blockedofcourse@foo.invalid> - 2017-03-31 02:16 -0700
        Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 11:39 +0200
          Re: Identification of modules Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-03-31 11:32 +0100
            Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 12:59 +0200
          Re: Identification of modules Don Y <blockedofcourse@foo.invalid> - 2017-03-31 11:55 -0700
    Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 11:30 +0200
  Re: Identification of modules rickman <gnuarm@gmail.com> - 2017-03-31 05:20 -0400
    Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 11:53 +0200
      Re: Identification of modules rickman <gnuarm@gmail.com> - 2017-03-31 06:16 -0400
        Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 12:39 +0200
          Re: Identification of modules rickman <gnuarm@gmail.com> - 2017-03-31 13:27 -0400
            Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 22:14 +0200
              Re: Identification of modules rickman <gnuarm@gmail.com> - 2017-03-31 17:48 -0400
                Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-04-03 10:57 +0200
    Re: Identification of modules John Devereux <john@devereux.me.uk> - 2017-03-31 11:39 +0100
      Re: Identification of modules rickman <gnuarm@gmail.com> - 2017-03-31 13:38 -0400
        Re: Identification of modules Piotr Wyderski <peter.pan@neverland.mil> - 2017-03-31 22:21 +0200
  Re: Identification of modules Joe Chisolm <jchisolm6@earthlink.net> - 2017-03-31 13:02 -0500
  Re: Identification of modules Tim Wescott <seemywebsite@myfooter.really> - 2017-03-31 16:18 -0500

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