Maximum number of USB devices – also shifting MIDI port assignments in MT (Revisited)


With Florian’s help, the issue of shifting MIDI port assignments was resolved.  For reference, what was happening is that, from one session to the next, the seven Akai APC Mini controllers in my setup would get reassigned to arbitrary MIDI in ports in MT.

Now, having added another two APC Mini controllers (for a total of 15 USB devices), the setup has become unstable again.  Depending on how I set up my USB hubs, I can only get 14 of the USB devices to be seen, and I seem to see the same shifting of MIDI ports as I had before… though I can usually get the assignments back to what I want by plugging them in – in a certain order.

What is troubling is that all the devices are always seen by Midiox, but that MT doesn’t see them until I fiddle around quite a bit.

Before I install another piece of software which may cause problems, I’d like to know if  the solution to shifting ports referred to in the link below has a chance of working.  It’s not clear to me that it would work for anything other than USB drives.

The pieces of software in question are referred to in the third post in this forum.

I’m hoping Florian gets to see this, since his efforts certainly helped before, and he understands my problem in depth.


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Posted by (Q&A Forum: 21, Answers: 116)
November 30, 2017 11:50 pm

Hi Gabriel,
I let Florian know about this posting. The only time I’ve had problems with MIDI USB recognition was
1) If I had my Iconnectivity monitoring the input and connected to my PC. Iconnectivity uses very generice port names when exposing to a controller
2) If there was another program holding the MIDI port.

Of course I seldom have more than about 6 USB MIDI devices attached at a given time.

( at December 1, 2017 5:39 am)

Hi Gabriel,
as you know, MT Pro has a bit more logic to not only support any number of MIDI devices, but also to keep consistent naming for differentiating multiple same devices. There is no limit in MT Pro regarding the maximum number of MIDI devices. We have run tests with hundreds of MIDI devices. So if a device is missing in your setup, it can be some kind of bug in MT Pro.

When you encounter the problem of the missing device, is it always an APC or can it also be a different device? Or are these 15 APC minis?

And just for the record, the “shifting” of same-name devices can occur with APC controllers because they don’t have a USB serial number. So MT resorts to the topology as reported by the OS — but that can change when rebooting, depending on the order the OS detects the USB hubs and the USB devices.


( at December 1, 2017 12:24 pm)
Private answer

Your explanation certainly helps.  I always wondered why there were 7 port hubs and not 8 port.  I do use all 4 USB ports on my laptop.  I think you know how I’m plugging my devices in, so I won’t belabor that point.  It sounds as if it may be stable if I use four 4 port hubs, and since I have 4 USB ports on my laptop, plug the hubs directly into the ports.  I’ll try that.

I have been using a 7 port hub with switches because it’s easier to get the system to map correctly by using the switches rather than to unplug and replug the cables, but since you are somewhat disinclined to use this type of hub, I’ll try 4 port hubs instead.

I’ll let you know about exclamation points in the device manager next time I have a failure.



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Posted by (Q&A Forum: 21, Answers: 116)
December 4, 2017 7:39 pm
Private answer

Hi Florian,

I previously thought that Midiox always saw all inputs no matter which hubs or laptop ports they’re plugged into, but this isn’t the case.  Instead, with Midiox, one of the X-touches isn’t seen.

The breakdown of MIDI devices is as follows:
8 Akai APC Minis
2 Novation ReMote Zero SLs
1 USB Roll Up Piano (61 keys)
2 Behringer X-Touch Minis

Additionally there are the following:
1 Qwerty keyboard
1 Mouse
1 Trackball

I believe the only way I’ve been successful in getting all devices to be seen simultaneously by MT is to do this:
– Input APC1-7 to the inputs of a 7 port hub (with its own power supply).
– Connect the output of this hub to an input of a 4 port USB powered hub
– Connect the output of the 4 port hub to USB port 1 on the laptop

– Input the following into another 7 port hub (which also has a power supply):
—- APC8
—- X-Touch 1
—- X-Touch 2
—- Roll UP Piano
—- Trackball
—- Mouse
—- Qwerty keyboard
– Connect the output of this hub to USB port 2 on the laptop

– Connect Zero SL 1 to USB port 3 on the laptop
– Connect Zero SL 2 to USB port 4 on the laptop

If I plug the output of the 7 port hub with APC 1-7 directly into the port on the laptop, one or more of the APCs is not seen by MT, but I believe that sometimes, one of the X-touches or Zero SLs is not seen.
This is all rather fluid, and plugging in and unplugging over and over gets tiring.  I’m quite sure this is what I see.  I think I’ll try a 10 input hub to see if I can eliminate plugging the 7 port hub into the 4 port, but I’m somewhat pessimistic.

Since the ports sometimes still get scrambled, I use a 7 port hub with switches to disable individual inputs.  That way I don’t have to actually unplug the devices.  I found that disconnecting them all then reconnecting in a certain order gave me a repeatably good mapping.


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Posted by (Q&A Forum: 21, Answers: 116)
December 2, 2017 10:46 pm

I wish I could shed some light here! Because of the flakiness, my first hunch would be some kind of hardware issue. Either with the hubs, or the devices, or power distribution.

In practice, USB hubs can get problematic the more you cascade them, some (cheaper) hubs just don’t handle it well. Also note that technically, there exist only 4-port hubs. So a 7-port hub is internally made of 2 cascaded 4-port hubs, and a 10-port hub uses 3 of them internally (that also explains why 7-port hubs are common and not 8-port hubs). Different ports on such hubs will be behind more or fewer hubs!
To minimize the hub cascades, you might get better off using a 4-port master hub, and connecting four 4-port hubs to it, giving you 16 USB ports, all of them on a 2-hub cascade.
That’s mostly theory, though, because different hubs work better or worse, and also in theory there shouldn’t be a problem with cascading a handful of hubs. A 10-port hub might in practice work better than a different 4-port hub…

And leveraging all USB ports on your computer also helps.

Very interesting would be to know if the device manager shows an exclamation mark with a failing device (if you’re on Windows).

Also note that technically, most USB hubs with switches do not conform to the USB specification. Physical unplugging/replugging is “safer” if you want to eliminate possible problem sources.

As said, I’m quite sure that MIDI Translator Pro handles any number of MIDI devices. We already have some internal automated tests for handling multiple devices of same name in MT Pro, but I’ll see if we can reproduce any problems with a setup like yours.

( at December 4, 2017 12:50 pm)