[TriEmbed] Raspberry Pi & Port Expanders

[Robert Gasiorowski]

Also, if you want to abandon expander and still have isolation, why not use
74HC540 or similar?

Rob.

On Mon, Nov 9, 2015 at 9:53 AM, Carl Nobile <carl.nobile at gmail.com> wrote:

> Brian,
>
> The only reason you may not want to use a port expander chip is if there
> are enough GPIO pins on the RPi to do what you need and in general serial
> communication whether it's I2Cor SPI will be slower than a parallel setup
> which you would get directly off the GPIO pins. I don't think speed is an
> issue with you though. The newer RPis have more pins on them and may lessen
> the need for port expander chips. Anyway, I feel you are doing fine the way
> you are.
>
> ~Carl
>
>
> On Mon, Nov 9, 2015 at 9:45 AM, Robert Gasiorowski via TriEmbed <
> triembed at triembed.org> wrote:
>
>> Yes there is, MCP23S17 and MCP23S08, both SPI.
>>
>> Rob.
>>
>> On Mon, Nov 9, 2015 at 9:22 AM, Grawburg via TriEmbed <
>> triembed at triembed.org> wrote:
>>
>>> as many of you already know I'm a big fan of using an I/O port expander
>>> (MCP23017 or MCP23008) when I'm working with anything that uses voltage
>>> other than 3.3 VDC. I want to make sure the Pi is fully isolated from the
>>> devices.  I realize that the Python coding is a bit more involved when
>>> using an I2C device and that it doesn't currently run on Python 3. I just
>>> think the trade-off with protecting the Pi is worth it.  Now, here's my
>>> question: Is there a situation when I should not use an I2C chip, keeping
>>> in mind the projects I'm dealing with are, by most standards, relatively
>>> basic?
>>>
>>> At tonight's meeting I'll have part of my pipeline valve and pump
>>> project that is using a single MCP23017 because I need more than 8 I/O
>>> pins. If there is an interesting alternative to the I2C I'd like to know
>>> about it.
>>>
>>>
>>> Thanks,
>>> Brian Grawburg
>>>
>>>
>>>
>>>
>>>
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>>
>>
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>>
>
>
> --
>
> -------------------------------------------------------------------------------
> Carl J. Nobile (Software Engineer)
> carl.nobile at gmail.com
>
> -------------------------------------------------------------------------------
>
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