View Full Version : Confused about usbMIDI

04-13-2016, 03:16 PM
HI folks,

I'm a french user of teensy boards and although musician.

I'm new in this forum but already used a teensy to build an IR driven time counter for archery competitions...

As I recently got an akai LPD8 USB-midi controller from a friend, I decided I'd build a (very) simple drone synth which synthesis parameters would be modified using the LPD 8. So I +5V powered my LPD8 and soldered its D+ and D- to the D+ and D- pads of the teensy.....but the controller stays asleep when I power my setup....(but it's recognized when I plug it in a computer)...

I'm now a bit confused because on one hand, I read this thread: https://forum.pjrc.com/threads/33639-Directly-connect-a-USB-MIDI-controller-to-a-Teensy. So if I'm not wrong, this means that teensy is NOT a usb midi host and then won't recognize the usb-midi gear attached to it.

And on the other hand I read the presentation page of usbMIDI library that tells teensy is capable of receiving USB-midi messages....

Except by bying a usbhost adapter to connect to the teensy so it can receive usbMIDI messages, is there a way for my LPD8 to be directly recognized by the teensy 3.2 I own ?

Thank you by advance !



04-13-2016, 10:04 PM
USB doesn't work this way. USB devices only talk to USB hosts. Teensy is a USB device. That LPD8 controller is (probably) also a USB device. They can not communicate with each other directly.

usbMIDI can receive message, when they are sent from the USB host.

But the USB hardware and protocol simply does not support device-to-device communication. Normally USB cables are made to only allow device-to-host connections. Cables that would create device-to-device connections are forbidden by the USB specification. If you make one by soldering wires, it will not work, because USB protocol does not support device-to-device communication.

04-14-2016, 09:05 PM
I use these (http://www.hobbytronics.co.uk/usb-host-mini) host adapters then connect to the teensy just like a simple serial interface which seems to work well with the midi controlers that I have tried (Korg and Novation).....

04-15-2016, 09:44 AM
Hi all !

@Paul: Thanks a lot for this really clear answer !! I now understand why my midi controller couldn't be recognized when plugged in teensy !

@houtson: Does this mean that I only need to solder RX and TX of the usb host to teensy's RX1 and TX1 ? Won't this RX and TX connections mess with the RX and TX used by the audio adaptor ?