[TriEmbed] "Latching" device

Carl Nobile carl.nobile at gmail.com
Thu Apr 10 09:31:29 CDT 2014


Something to be aware of is that the MCP23017 is a 5V device not a 3.3V
device. It seems to work without a level converter, but could fail on some
occasions like when adding more than one load to the output pins of the
RPi, so it's best practice to always use a level converter between the RPi
and a MCP23017.

Carl



On Thu, Apr 10, 2014 at 9:31 AM, Bill Farrow <bill at arrowsreach.com> wrote:

> I was wondering if there is a "tricky" way you could do this using
> only a single pin, a capacitor, and a resistor.
>
> When the push button connects it charges the capacitor. The MCU pin,
> configured as an input, can read the state of the capacitor. When the
> MCU wants to reset the latch it can change the pin to an output and
> set it to 0 (low) which discharges the capacitor to ground via the
> resistor.
>
> Let's see how bad my ascii art is:
>
> mcu pin --- resistor --- switch --- 3.3v
>                              |
>                        capacitor
>                              |
>                            GND
>
> Bill
>
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> TriEmbed web site: http://TriEmbed.org
>



-- 
-------------------------------------------------------------------------------
Carl J. Nobile (Software Engineer)
carl.nobile at gmail.com
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