On Wed, June 6, 2012 8:10 pm, Isaac Marino Bavaresco wrote:
> Em 6/6/2012 20:41, Marcel Duchamp escreveu:
>> Looking for a 1-to-8 mux that will run from a 3.3V PIC32.  It will be
>> driving servo signals. It looks like a '595 is just out of range to
>> reliably work.
>>
>>
>> Any suggestions?
>
>
> You are in the right path. You can use a 74HCT or 74AHCT device powered
> by 5V. Its inputs will understand the 3.3V CMOS outputs
> Fill a shift-register with zeros then walk a single '1' across all the
> outputs, waiting the necessary pulse width for each output. Repeat every
> 20ms.
> It takes just 2 I/Os, clock and data. The chain can have up to 10
> outputs and yet ensure correct timing for all the servos (2ms x 10 =3D
> 20ms).

The PIC32 has 5V compatible pins- you can pull them up to 5V with an
external resistor and run the I/Os as open drains.  Not as fast as an
active pull-up/pull-down, but definitely cheaper, and probably good enough
for RC servos.

Not all the pins are 5V compatible though, you have to double check on the
data-sheet.



Matt Bennett
Just outside of Austin, TX
30.51,-97.91

The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with.
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