[sdiy] MIDI phantom power...over 5 pin MIDI connector ?

[Tom Wiltshire]

While this is all true, the typical 5V/220R setup is so common it's become a virtual standard, so I wouldn't bash people for treating it like one. In fact, it even features on the MMA website, although it is

http://www.midi.org/techspecs/electrispec.php

Neil's discussion with the MMA is very interesting too ( http://www.midi.org/cgi-bin/forum/forum.pl/forum.pl?m-1171180161/s-all/ ). The admin clearly says "We feel the specification is unambiguous about the 5V." although that's hardly true, and it makes much more sense to specify a 5mA current rather than a 5V level. It seems to me that they're wanting to retroactively tweak the spec to allow for the MIDI-powered stuff that people have done assuming that there'll be 5V available. There was a time when this was *almost* certainly true, but that was a long while ago now.

Personally, I've been using dsPICs a lot in the last few years, so I've had to think about using MIDI with a 3.3V processor. That requires changing those 220R resistors, but as Neil points out, the spec doesn't deal with voltages, so there's no problem at all either receiving or sending from a 3.3V uP.

However, for the OP, this needs to be something to consider. Will your phantom powered MIDI device still work if I connect it to my (standards compliant) gizmo which uses a 3.3V uP?

Tom


On 10 Sep 2015, at 09:58, Neil Johnson <neil.johnson71 at gmail.com> wrote:

> What I find particularly funny/frustrsating/disappointing is how many
> people don't understand the MIDI spec.
> All this talk of "5V" and "220R resistors" completely misses the point.
> 
> *sigh*
> 
> Here's a clue: the text of the standard makes no mention of voltage.
> Chapter 2, page 1, "HARDWARE".  The circuit given on page 2 is an
> illustration of one implementation.  I've also discussed the wording
> in the standard with the MMA and their response to the vagueness in
> the standard is "well no-one's pointed this out before, and we don't
> quite understand why the spec was written in this way, so, umm, la la
> la la..."
> 
> 
> Neil