[sdiy] Possible MIDI interface powered by MIDI driving device...

[Dave Leith]

MIDI Solutions still make a series of MIDI utility boxes that run off MIDI
power. Spliters, mergers and filters...mostly they work as they should, but
occasionally they don't. I own a DSI Tempest which will not work with them.
I am pretty that the boxes are the problem not the MIDI specifications and
build from Dave Smith. I haven't ever opened them up to see what's inside
which would ruin the cosmetic finish....

On Thu, Mar 24, 2016 at 9:16 PM, <rsdio at audiobanshee.com> wrote:

>
> On Mar 24, 2016, at 5:09 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
> > On 24 Mar 2016, at 20:24, Olivier Gillet <ol.gillet at gmail.com> wrote:
> >>> Steve T's comment about 5V not being a reliable supply suggests to me
> that for things like this (let's call it "creative rule-bending"?!) we
> should use uPs that can operate from 5V down to 3V or so. There are such
> things, so this shouldn't be too difficult to organise.
> >>
> >> The value of the resistors on the OUT side depend on the supply
> >> voltage. If the MCU is powered by 3.3V, they should be much lower than
> >> 220 ohm (about 50 ohm) - otherwise you won't be sending enough current
> >> in the loop!
> >
> > Ah, yes, of course. Good point, Olivier. I was only thinking of the IN
> side.
> >
> > I suppose you could use the uP to detect its own power supply voltage
> and adjust the outgoing current accordingly, but at that point, it's all
> starting to get a bit more complicated than it's worth for a thing that
> removes 0xFE from a MIDI stream.
>
> It is not typical for a uP to have adjustable control over the outgoing
> current from a GPIO port pin. It is fairly common for a uP to have some
> sort of A/D pin that could be used to measure the supply voltage, but
> turning that into a variable output current would require additional
> resources. In other words, I agree that this is getting a bit more
> complicated than it's worth for something that is desired to be "simple."
>
> Brian
>
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