BBB GPIO pin output capability

[Chris Green]

I can't find this anywhere in the System Reference Manual. What is
the drive capability of the BBB output pins? Also what is the best way
of buffering them so they won't get any bad voltages fed back into
them?

--
Chris Green
·

[Stephen Lentz]

6 mA.

Voltage dividers, 5k1 resistors going into the pin, filter capacitors and TVSS. Use more than one, better yet all of them. Or buy a crate of BBs cause you’ll burn out a few while prototyping. Don’t ask me how I know.

Best Regards,
Steve Lentz

> On Nov 15, 2022, at 4:33 PM, Chris Green <c...@isbd.net> wrote:
>
> I can't find this anywhere in the System Reference Manual. What is

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[Chris Green]

Stephen Lentz <stl...@gmail.com> wrote:
> > On Nov 15, 2022, at 4:33 PM, Chris Green <c...@isbd.net> wrote:
> >
> > I can't find this anywhere in the System Reference Manual. What is
> > the drive capability of the BBB output pins? Also what is the best way
> > of buffering them so they won't get any bad voltages fed back into
> > them?
> >

> 6 mA.
>
OK, thank you, that's loads more than I need so no problem there.

> Voltage dividers, 5k1 resistors going into the pin, filter capacitors and
> TVSS. Use more than one, better yet all of them. Or buy a crate of BBs
> cause you’ll burn out a few while prototyping. Don’t ask me how I know.
>

:-) I've not killed any of my (3) BBBs yet. I was very careful with
buffering on the one that is actually doing live monitoring. It's
outputs drive the 'outside world' through some Hobbytronics level
converters and that seems to have kept the BBB safe.

I think I'll probably just use another of the level converters on the
one more output I'm going to use.

--
Chris Green
·

[Steve Lentz]

Yep, be careful of things like 4-20 mA sensors, they often send 24V to the output when being turned on. That’s where some capacitance across the input pins will really help. For motor controllers or anything vaguely industrial, it’s best to use optocouplers, I’ve had good results with VO618As. I2C devices are pretty tame, not a lot needed for these.

-Cheers

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