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

[Dave Brown]

The AV2313 will work down to 2.7V.  The V version will go lower than that,
but of course you have no headroom to drive the MIDI out current.  I think I
reliably got around 4V of Vcc which is why I selected 150R as the MIDI out
resistors.  I got enough variation from different synths that doing an
internal RC oscillator wasn't stable enough.  Rather than waste headroom for
regulation, I went with the crystal.  Note also that I am stealing power
from both pins on the MIDI input connector.  While the schematic shows
1N4148s I used Schottky diodes to minimize any drop.

Dave

> -----Original Message-----
> From: Tom Wiltshire [mailto:tom at electricdruid.net]
> Sent: Thursday, March 24, 2016 12:53 PM
> To: Dave Brown
> Cc: 'Jean-Pierre Desrochers'; Synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Possible MIDI interface powered by MIDI driving
device...
> 
> Nice work, Dave. I always enjoy having a look at someone else's approach
to
> stuff I've thought about or worked on.
> 
> 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.
> 
> Tom
> 
> 
> On 24 Mar 2016, at 18:47, "Dave Brown" <davebr at modularsynthesis.com>
> wrote:
> 
> > I did my own AVR design of a MIDI processor powered by the MIDI device.
> > Details, including code, are at
> > http://modularsynthesis.com/processor/processor.htm
> >
> > I use this for a variety of reasons, but one of which is filtering out
> > Active Sensing and Timing Clock.  Note that power stealing isn't
> > supported by the MIDI standard and people on this list have criticized
> > me for doing so, but it works quite well on a number of different
> > synths.  Unlike what you posted, I went with an unregulated supply and
> > a crystal for the AVR so the timing would be accurate.  I found that
> > combination worked better.  All you have to do in the code is strip
> > out the commands that echo the byte to the output.  You can strip the
> > transpose and stuff also or just hardwire the pins.
> >
> > Borrow away ...
> >
> > Dave
> >
> >> -----Original Message-----
> >> From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] On
> >> Behalf Of Jean-Pierre Desrochers
> >> Sent: Thursday, March 24, 2016 11:13 AM
> >> To: Synth-diy at dropmix.xs4all.nl
> >> Subject: [sdiy] Possible MIDI interface powered by MIDI driving
device...
> >>
> >> Here is a possible MIDI interface that would sink its power from a
> >> MIDI driving device...
> >>
> >> http://www.arcenson.com/public/MIDI_interface_power_steeler.JPG
> >>
> >> ---> Assuming that the driving MIDI device (keyboard, sequencer,
> >> ---> pedal board, etc..) is powered by internal +5VDC supply..
> >> The CPU would have to sink its 5vdc thru the 220 resistor of the
> >> driving device. Doable..
> >> I also think that it could work since the CPU MIDI output would be
> > 'opticaly'
> >> linked with the final receiving MIDI device.
> >> Both driving and receiving devices would avoid ground loops while a
> >> CPU process is running between them..
> >>
> >> A friend of mine asked for a simple 'MIDI active sensing code (FE)'
> >> hardware filter working without a DC supply..
> >>
> >> JP
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