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Re: Identification of modules

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On 3/31/2017 3:21 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.
>
> 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.
>
> 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?
>
> 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.

I'm not clear on what you are using the resistive divider for.  Is that 
to identify the module type or the slot?

The lowest priced 1 wire part I found on Mouser is the DS28E05P+T.  It 
combines the unique 64 bit serial number each 1 wire device has with 112 
bytes of user EEPROM for under $0.50 in quantity.  The EEPROM can be 
programmed in manufacturing to provide a module type identification 
number.

I'm not clear on what your limitations are for identifying the slot 
number.  The easy way is to isolate the 1 wire buses to each slot so you 
are only talking to one at a time.  If you don't want to use that many 
pins on your MCU, an analog switch multiplexer will allow the MCU to 
talk to one slot at a time and only need log2(N) I/Os.

-- 

Rick C

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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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