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Re: I2C Communication between two Microcontrollers

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On 7/7/2022 19:19, chris wrote:
> On 07/06/22 10:52, David Brown wrote:
>> On 06/07/2022 10:27, Stephen Pelc wrote:
>>> On 6 Jul 2022 at 09:52:23 CEST, "pozz" <pozzugno@gmail.com> wrote:
>>>
>>>> I found that I2C peripherals embedded in most of MCUs are very complex
>>>> and most of the time they aren't reliable.
>>>> After some testing, I usually decide to write a bit-banging I2C code.
>>>
>>> I have to agree here. I2C is conceptually simple, bu it is an edge
>>> triggered
>>> protocol and is very sensitive to noise unless you use buffer 
>>> devices. It
>>> is excellent for master devices, but writing the slave software is
>>> much more
>>> complex to cover all cases.
>>>
>>
>> A key problem for I²C is the multi-drop nature of the lines. The edges
>> themselves are not the big problem, it is the weak pull-up that leaves
>> the lines very susceptible to noise and interference. SPI has edges, as
>> do most protocols with a clock signal, but there the master drives high
>> and low, giving a far more "solid" line.
>>
>> I²C can be fine in simple cases, but there are several less-used
>> features that complicate it, especially when used together. That
>> includes multi-master, clock stretching, 10-bit addressing, and newer
>> faster speeds. Good luck trying to make a microcontroller slave that
>> works with all of that!
>>
>> There is also the possibility of bus hang and invalid states. This can
>> hit you during development - if you stop your microcontroller and
>> restart it (perhaps with a new program version) in the middle of an I²C
>> transaction, you can leave the slaves stuck - they may need a reset or
>> power-cycle to recover.
> 
> The original Iic from Philips was for consumer equipment and has
> worked well for that sort of application, but it's not robust enough
> for professional work imho. I would never use it unless an io
> device needed it, such early Teletext devices. As you say spi
> is a far better sorted design...
> 
> Chris

I basically agree but things are not that bad as long as one
does not push things too far. For me the worst part has been dealing
with in-built I2C controllers, used two and both worked but each
took me *days* to defeat - unlike the first time I used I2C
some decades ago, bitbanging it from a HC11, which took me
only an hour or two.  Never used an MCU as an I2C slave yet, may
do so soon but who knows.
The peripherals I have used - some eeprom, RTC, ADC and perhaps
some I can't think of now have all behaved; of course one has to
deal with hanged bus situations, I have not seen a part which
needs repower to get fixed (must have been lucky I guess).
I have managed to upset the bus, being open drain, routing it
too close to a flyback convertor switch, the latter doing 100V
excursions "pretty fast" (tens of ns for the 100V I think).
Changing the pullups on the I2c from 2k to 1k fixed that
(still not that much of "too close", some luck again :).

======================================================
Dimiter Popoff, TGI             http://www.tgi-sci.com
======================================================
http://www.flickr.com/photos/didi_tgi/

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I2C Communication between two Microcontrollers Neelakantappa M <neelakantamaagi253@gmail.com> - 2022-07-05 06:28 -0700
  Re: I2C Communication between two Microcontrollers pozz <pozzugno@gmail.com> - 2022-07-05 16:22 +0200
  Re: I2C Communication between two Microcontrollers Richard Damon <Richard@Damon-Family.org> - 2022-07-05 22:33 -0400
  Re: I2C Communication between two Microcontrollers David Brown <david.brown@hesbynett.no> - 2022-07-06 08:49 +0200
    Re: I2C Communication between two Microcontrollers pozz <pozzugno@gmail.com> - 2022-07-06 09:52 +0200
      Re: I2C Communication between two Microcontrollers Stephen Pelc <stephen@vfxforth.com> - 2022-07-06 08:27 +0000
        Re: I2C Communication between two Microcontrollers pozz <pozzugno@gmail.com> - 2022-07-06 11:20 +0200
          Re: I2C Communication between two Microcontrollers Stef <me@this.is.invalid> - 2022-07-06 13:43 +0200
          Re: I2C Communication between two Microcontrollers Stephen Pelc <stephen@vfxforth.com> - 2022-07-06 15:49 +0000
        Re: I2C Communication between two Microcontrollers David Brown <david.brown@hesbynett.no> - 2022-07-06 11:52 +0200
          Re: I2C Communication between two Microcontrollers chris <chris-nospam@tridac.net> - 2022-07-07 17:19 +0100
            Re: I2C Communication between two Microcontrollers Dimiter_Popoff <dp@tgi-sci.com> - 2022-07-07 19:49 +0300
              Re: I2C Communication between two Microcontrollers Richard Damon <Richard@Damon-Family.org> - 2022-07-07 23:22 -0400
                Re: I2C Communication between two Microcontrollers Mike Perkins <spam@spam.com> - 2022-08-05 22:07 +0100
                Re: I2C Communication between two Microcontrollers Richard Damon <Richard@Damon-Family.org> - 2022-08-05 21:10 -0400

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