MIDI Sprout

Discussion (*ask your questions here!) => Development => Topic started by: drc3p0 on December 24, 2017, 03:48:45 PM

Title: USB midi not working
Post by: drc3p0 on December 24, 2017, 03:48:45 PM
I have a generic USB midi adapter that I've been using to send midi data to my raspberry pi.  it works with my midi keyboard but not with the midisprout.  Has anyone found a USB midi device that actually works?  I don't think the USB midi device is even transmitting the midi signal since the indicator light isn't turning on.  This is going into a python script so I don't know a workaround since software isn't an option. 

Any ideas?
here's a short video demoing the led not turning on. 
Title: Re: USB midi not working
Post by: Nicola Alexandra Hajdu on February 27, 2018, 04:48:02 AM
Looks like there are not many around having an experience with MIDI-Sprout connected through Raspberry instead PC, Mac, iOS & Android. Your remaining choice is a meager path, where you have to try out a couple of USB MIDI devices. If i were in your situation i would start with Creative Emu xmidi & then Roland UM-One MkII etc...

Much Love
Title: Re: USB midi not working
Post by: manuel on April 14, 2018, 09:59:43 AM
Also had problems with these cheap USB2MIDI adapters initially.

They seem to be not very MIDI style, as the opto-isolator is not populated in many of them.

I followed this blog post to fix mine, by adding that optocoupler:

May not be feasible for everyone.

But I'll see if it works with one of my fixed adapters and a Raspberry Pi, so you know if its worth getting another adapter.
Title: Re: USB midi not working
Post by: sam on April 14, 2018, 04:58:48 PM
Excellent work manuel!!  repairing the low cost USB/MIDI units is definitely a challenge.  if a manufacturer skimped on the opto isolator, the unit probably doesn't have a very strong clock or power regulation.

So I know many of you are wondering, "why does this cheap adapter work with a MIDI keyboard by doesn't work with the Sprout?"

Because the MIDI Sprout is measuring conductivity, I try to isolate the Sprout circuit as much as possible from the host Synth/computer.  In a perfect MIDI environment, the optoisolator is all that would be needed.  But ... most MIDI Keyboards and devices don't really care about isolation, they are perfectly happy to 'share a ground' between the MIDI Keyboard and the host.  When looking at the 5 pin DIN MIDI Jack, I do not attach 'ground' (the middle pin).  Ground connection should not be required between a MIDI source and host. 

On those cheap MIDI cables, the Ground is 'connected' and the optoisolator is 'bridged', this would result in the MIDI Sprout being connected to both the plant and the host computer which is essentially a noisy loaded mess.  Medical equipment is isolated using a variety of expensive components, the Sprout is expecting the host to have an isolator installed.

On the side of the board with the LEDs and solder connections, you can see pads which can be used to 'bridge' MIDI ground pin to the Sprout board Ground, this will allow some usage (albeit not great functionality) with hosts which require Ground connection.  But .... Please don't do it, i disconnected ground for a reason ;)

Title: Re: USB midi not working
Post by: Nicola Alexandra Hajdu on April 16, 2018, 01:17:26 PM
This is an interesting read which needs to be shared, so potential MIDI-Sprout Users won't ever thinking on acquiring a cheap USB-MIDI adapter or IF they are versed enough in electronics EXPECT to fix it. I can wholeheartedly & confidently recommend the Creative's E-MU Xmidi 1x1 Tab.

Thank you Sam & Manuel for brainstorming!

Much Love