Groups > sci.electronics.design > #453679

Re: Output boards, SPI vs I2C

From	David Lesher <wb8foz@panix.com>
Newsgroups	sci.electronics.design
Subject	Re: Output boards, SPI vs I2C
Date	2017-03-26 04:11 +0000
Organization	NRK Clinic for habitual NetNews Abusers - Beltway Annex
Message-ID	<ob7f1h$ktg$1@reader1.panix.com> (permalink)
References	<ob4lm9$k58$1@reader1.panix.com> <ob6b9p$9a2$1@dont-email.me>

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rickman <gnuarm@gmail.com> writes:

....

>All things being equal (whatever that means as I2C and SPI
>have very little equal) I would pick SPI for driving 24 relays
>because the "protocol" should be very simple (shift out the
>data) and I2C can be more complex to implement.

>I'd probably wire three boards serially and see if that works.
>If not, I would wire them in parallel with three separate chip
>selects.

This would be driven by a
<http://www.digital-loggers.com/plchw.html> 
which claims to support both flavors.

Data rate is virtally irrelevent here; I need a response time
far slower than the relays themselves are.....

My hand may be forced by what boards are actually available. I
found <https://www.industrologic.com/r8spiprod.htm> and 
<http://lightsosoft.com/sites/default/files/I2C-Relay8-H_040813_1240.pdf>
but many other boards are not what they seem to be, or are from across the pond.
<http://jap.hu/electronic/relay_module.html>

Not sure I grasp "wire three boards serially" but we can spare chip select 
outputs.
-- 
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Thread

Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-25 02:46 +0000
  Re: Output boards, SPI vs I2C krw@notreal.com - 2017-03-24 23:25 -0400
    Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 04:13 +0000
  Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-25 14:04 -0400
    Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 04:11 +0000
      Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-26 02:37 -0400
        Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 14:41 +0000
          Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-26 12:47 -0400
            Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 19:49 +0000
              Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-27 10:49 -0400
                Re: Output boards, SPI vs I2C Jasen Betts <jasen@xnet.co.nz> - 2017-03-27 18:41 +0000
                Re: Output boards, SPI vs I2C Martin Riddle <martin_ridd@verizon.net> - 2017-03-27 19:07 -0400
                Re: Output boards, SPI vs I2C Jasen Betts <jasen@xnet.co.nz> - 2017-03-28 08:03 +0000
                Re: Output boards, SPI vs I2C Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-28 10:44 -0400
                Re: Output boards, SPI vs I2C Jasen Betts <jasen@xnet.co.nz> - 2017-03-28 18:59 +0000
                Re: Output boards, SPI vs I2C Martin Riddle <martin_rid@verizon.net> - 2017-03-28 15:37 -0400
                Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-04-03 17:49 +0000
                Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-04-03 15:18 -0400
                Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-04-04 02:59 +0000
                Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-04-04 00:54 -0400
                Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-28 05:08 +0000
                Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-28 02:16 -0400
  Re: Output boards, SPI vs I2C Martin Riddle <martin_ridd@verizon.net> - 2017-03-27 19:03 -0400
    Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-28 03:28 +0000
      Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-28 00:38 -0400
        Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-28 14:47 +0000

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